Assessing the efficacy of duration and intensity prescription for physical activity in mitigating cardiometabolic risk after spinal cord injury

Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR. Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity. Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI. To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al. [80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI. Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52. 12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53]. Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59. 6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3). Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31].Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1).Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e., upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity.In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives.We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.Purpose of reviewSpinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (>= 6 METs) and dedicating 250-300 min/week (approximate to 2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.Papers of particular interest, published within the annual period of review, have been highlighted as:Spinal cord injury (SCI) leads to the disruption of motor and sensory signals due to traumatic or atraumatic insult to the ascending and descending tracts of the spinal cord. Following the injury, rapid physical deconditioning ensues in an obesogenic environment [1] due to autonomic dysregulation [2], "adaptive" cardiac atrophy [3], attenuated vital capacity [4], and sublesional myopenia [5]. Consequently, this leads to an 18% reduction in basal energy metabolism [6] and a 27% reduction in resting energy metabolism [7-9]. In conjunction with reduced whole-body energy expenditure, sedentary behavior [10], and a concomitant accumulation of total body fat [11], a heightened cardiometabolic risk (CMR) emerges (Fig. 1). The early progressive nature of the CMR substantially contributes to the deterioration of overall health and physical function [12], thereby underscoring the pivotal role of countermeasures in mitigating CMR.Cardiometabolic Risk Cascade in the Context of Spinal Cord Injury (SCI). The diagram illustrates the complex interconnected pathways of risk factors through the interplay of modifiable and nonmodifiable risk factors, leading to the progression of cardiometabolic risk and subsequent development of cardiovascular disease and mortality. Specifically, neurogenic obesity, resulting from spinal cord injury, is depicted as an essential instigator and is linked to many modifiable and nonmodifiable risk factors related to cardiometabolic risk. Nonmodifiable risk factors interact with modifiable ones, enhancing the vulnerability to chronic diseases. However, modifiable risk factors modulate the trajectory of nonmodifiable risk factors and their disease progression. Cardiometabolic risk, fueled by both categories of risk factors, propels the advancement of cardiovascular disease and mortality. Cardiometabolic syndrome also directly contributes to various chronic neuroendometabolic disorders. Major modifiable risk factors are denoted by an asterisk (*). Arrows indicate the connection and progression between factors and chronic diseases. HDL-C, high-density lipoprotein cholesterol; T2DM, type 2 diabetes mellitus. Visualization was created using Biorender.For persons with and without SCI, authoritative guidelines established by expert panels endorse physical activity (PA) interventions as a practical approach to mitigating CMR [13-15,16,17,18-20]. However, compared to those without SCI, these PA guidelines may benefit from an additional evaluation of the diminished cardiorespiratory response to physical exertion in individuals with SCI [21-23]. Consequently, the initial prescription of PA may inadvertently lead to an insufficient PA volume by underestimating the duration and intensity required to address CMR effectively. To counteract physical deconditioning, optimize function, and mitigate CMR after SCI, a reevaluation of PA prescriptions is necessary to account for physiological responses that differ from those without SCI. By considering these unique physiological factors, the PA prescription can be tailored to better meet the specific needs and limitations of individuals with SCI, thereby optimizing their outcomes and minimizing the impact of CMR. This monograph assesses the duration and intensity of PA needed to manage CMR after SCI. In the present paper, we aim to concentrate on the PA-induced energy expenditure aspect of the energy balance equation and direct readers to other papers that delve into energy intake [24,25,26,27]. no caption availableCMR denotes a constellation of modifiable and nonmodifiable risk factors that heighten the susceptibility to cardiovascular disease (Fig. 1) [28], with hypertension, heart failure, cardiac dysrhythmias, and atherosclerosis as significant contributions to cardiovascular morbidity in SCI [29]. Similarly, cardiometabolic syndrome (CMS) arises from the clustering of distinct endometabolic and vascular abnormalities, presenting itself as both a "silent killer" and an "early warning signal" for chronic and potentially disabling disorders (Fig. 1). While the definitions for specific component risk factors of CMS may not entirely align [28], their collective presence amplifies the threat of common chronic cerebrovascular, cardiovascular, endocrine, and neurological disorders associated with disability [30]. Commonly recognized component risk factors for CMS are dyslipidemia, hypertension, dysglycemia/insulin resistance, and obesity [31]. Obesity, resulting from a positive energy balance in which total energy intake exceeds expenditure [32], is widely recognized as a major contributor to CMR, CMS, and disability [33]. The Spinal Cord Medicine Clinical Practice Guidelines on CMR after SCI identify obesity as the predominant CMR factor within the population with SCI [18]. Several studies have also demonstrated that CMS is associated with a decline in independence [34], cognition [34], strength [35], and mobility [35-38], such that obesity is itself a risk factor for mobility limitations [37]. Where individuals with SCI co-present with obesity and CMS [39-41], they will likely encounter additional disability, partly due to increasing body weight resulting from excess body fat. While PA is now recognized as a vital sign [42], the absence of it should be regarded as a CMR factor for persons with SCI.Although this monograph focuses on PA, defining PA relative to rehabilitation and exercise programs is essential in understanding effective PA prescription and long-term management. PA, exercise, and rehabilitation programs share the common objective of enhancing overall health and well being through the utilization of aerobic and resistance training modalities. However, their definitions and foci diverge in their emphasis and implementation approaches (Table 1). Both PA (including exercise) and rehabilitation incorporate progressive physical exertion to reduce the physical, psychological, and economic burden of morbidity by decreasing disability, optimizing mobility, improving coordination and balance, strengthening muscles, and increasing activity-based energy expenditure (i.e., "exercise" energy expenditure). Independent of an SCI, these are universal benefits of PA. Particularly for people with SCI, often presenting with multiple comorbidities, an increase in physical activity is needed to improve and maintain physical function and health and offset physical deconditioning [14].Glossary of terms [1]The volume of PA is determined by frequency, duration, and intensity [36], components utilized in prescribing PA and rehabilitative therapies. Frequency is the number of days per week dedicated to PA, whereas duration is the cumulative amount of activity completed within a specified period, usually one week. Duration is commonly expressed in measures of energy expenditure over the specified period (kilocalories [kcal]/week). Intensity can be categorized into light, moderate, and vigorous intensity levels [43]. These levels are determined by the exerted effort during the activity and the subsequent rise in cardiorespiratory activity and energy expenditure, without consideration of physiological capacity. While important throughout the lifespan and continuum of care, rehabilitation activities after SCI are likely conducted at insufficient intensities to reduce CMR factors [44]. This highlights the importance of lifelong engagement in PA to address such risks. However, there is a need to assess whether the prescribed duration and intensity of PA are sufficient for effectively managing the pathogenic associations between dyslipidemia, dysglycemia/insulin resistance, hypertension, and obesity and their role in the development of cardiovascular disease (Fig. 1). Authoritative PA guidelines from the American College of Sports Medicine (ACSM) [13], the World Health Organization (WHO) [14], the United States (US) Department of Health and Human Services [15], and the European Association for the Study of Obesity PA Working Group [16] are in similar agreement with the WHO PA Guidelines for People Living with Disability [17] and the Paralyzed Veterans of America Clinical Practice Guidelines on CMR after SCI [18]. These guidelines generally recommend that individuals participate in at least 150 min/week of moderate-intensity PA, with some guidelines providing an upper limit of up to 300 min/week [14,15,17]. Regarding vigorous-intensity activity, the ACSM [13], WHO [14], the WHO PA Guidelines for People Living with Disability [17], and the US Department of Health and Human Services [15] recommend between 75-150 min/week. Alternative guidelines to meet recommendations include engaging in at least three 10-min bouts of PA throughout the day to interrupt periods of prolonged sedentary behavior [18]. PA is recommended as soon as possible following the SCI according to individual ability, given that individuals with SCI often spend a considerable amount of time, if not the entire day, sitting in their wheelchairs [14]. This will maintain functional, physical, and muscular fitness to reduce CMR.Meeting specific thresholds for PA intensity, duration, and energy expenditure is imperative to address CMR. While the initial emphasis of PA recommendations was placed on promoting moderate-intensity activity due to its perceived attainability for a wider population [45], research consistently indicates the superior physiological effects of engaging in sustained, vigorous-intensity PA in reducing CMR factors, cardiovascular disease, and all-cause and cause-specific mortality [46-52]. ACSM particularly recommends utilizing intensities exceeding an oxygen consumption of 1.5 L/min or 21 ml/kg/min (denoting vigorous intensity) to reduce the risk of cardiovascular disease [53].Multiple mechanisms likely mediate the cardiometabolic benefits of regular PA by increasing high-density lipoprotein cholesterol and decreasing triglycerides [54], lowering blood pressure [55], improving glucose metabolism and insulin sensitivity [56], reducing inflammatory markers [57], increasing energy expenditure [58,59], and decreasing body mass [60-62]. Improvements in these CMR factors explain 59% of the reduction in cardiovascular disease [63]. In contrast, the remaining 41% may originate from enhanced endothelial function [64], improved vagal tone resulting in lower heart rates [65], vascular remodeling producing larger vessel diameters, and enhanced bioavailability of nitric oxide [66,67]. These findings are also reinforced by a curvilinear dose-response relationship between PA intensity [68] and duration [69] and the mitigation of cardiovascular risks. As PA volume increases, it places heightened demands on the cardiorespiratory system, improving endurance [70], and promoting muscular endurance and hypertrophy [71]. In persons with SCI, the evidence on the effectiveness of vigorous-intensity PA in reducing CMR factors has predominantly documented improvements in glycemia/insulin resistance [72-77] while observing limited enhancements in lipid profiles [78] and blood pressure [78]. At face value, these findings may indicate that vigorous-intensity PA is insufficient to reduce CMR after SCI. However, these findings can be attributed to several factors, including the limited statistical power, type of PA (i.e. , upper-body PA, functional electrical stimulation, etc.), the definition of vigorous/high-intensity, and the specific duration of training implemented by the investigators.The utilization of metabolic equivalents of task (METs) enables quantifying light-, moderate-, and vigorous-intensity PA, facilitating comprehensive assessments of physical fitness and metabolism [79]. A MET signifies the oxygen consumption per unit of body mass during seated rest; it enables the prescription and evaluation of PA intensity as a multiplier of resting metabolism and can be used to express oxygen consumption and exercise energy expenditure [13,43]. A single MET is 3.5 mL/kg/min (0.245 L/min) in individuals without SCI. After SCI, a MET is 2.7 mL/kg/min (0.189 L/min) [80], approximately 30% lower than persons without SCI. This reduced MET value, first reported by Collins et al.[80] in SCI, is based on multiple factors, including decreased energy metabolism [6], limited oxygen utilization in sublesional active skeletal muscle [81], sympathetic nervous system dysfunction [82], an injury level-reduced cardiorespiratory response [83], and circulatory hypokinesis that hampers the hemodynamic response by restricting venous return and subsequently diminishing cardiac output [23]. Higher injury levels, often necessitating hand-securing devices for upper body PA modalities [84], exacerbate these factors [80]. In cases of tetraplegia, individuals exhibit a weighted mean peak oxygen consumption of 0.87 L/min, in contrast to the 1.51 L/min in paraplegia, reflecting a notable 54% difference [83]. Achieving and maintaining these peak values of oxygen consumption after SCI over extended periods of time poses considerable challenges because of muscle and cardiorespiratory limitations and fatigue [85,86]. To engage in vigorous-intensity activity, a sustained minimum oxygen consumption of approximately 1.13 L/min would be required. Therefore, PA may require a longer duration for most individuals with SCI, as tetraplegia accounts for 59.6% of the population with SCI [87].In 2001, the ACSM recommended 200-300 min/week of moderate-intensity PA for long-term weight loss related to CMR reduction of obesity [88], and other published guidelines also recommend that greater amounts of PA may be needed to prevent weight regain after weight loss [89]. In a recent ACSM position statement on weight loss and prevention, Donnelly et al.[90] reported that achieving significant weight loss and effectively preventing weight regain requires an exercise energy expenditure of 2000 kcal/week through approximately 250-300 min/week of moderate-intensity exercise. Additional evidence suggests that a modest 5-10% reduction in body weight produces significant clinically relevant improvements in CMR, with greater weight loss having greater benefits [91-94]. Notably, substantial improvements in blood pressure, glycemic control, and lipids are linked to the extent of weight loss at the one-year mark [91]. Considering the reduced response to physical exertion, achieving sustained levels of oxygen consumption necessary for engaging in vigorous-intensity activity may become a formidable task for many with SCI. Therefore, extending the duration of PA may prove vital in increasing energy expenditure and effectively addressing CMR factors, with a particular focus on combating obesity. In the quest to optimize PA prescription for individuals with SCI, it is prudent to briefly consider psychosomatic intensity measures such as the Borg scale and the talk test (Table 2) as surrogates for physiological response. The Borg scale aligns perception with physiological responses in the subpeak PA range. Similarly, the talk test correlates speech comfort with PA ventilatory threshold [95]. However, in contrast to the talk test in persons with paraplegia [96], caution is advised when applying the Borg scale to subjects with autonomic impairment (e.g., injury level T6 and above) due to potential deviations from the linear heart rate responses established for subpeak PA ranges [96,97]. Therefore, careful consideration is essential when employing these psychosomatic indicators to evaluate PA intensity, given their variance from physiological responses observed in individuals without SCI.Physical activity intensity levels with corresponding oxygen consumption and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI)1 L of oxygen is equivalent to 5 kcal [4,5].Table 2 illustrates intensity levels with their corresponding MET equivalents, oxygen consumption, and exercise energy expenditure in theoretical gender (male)- and weight (70 kg)-matched individuals with and without SCI. The calculations using constants from the ACSM [13] demonstrate diminished oxygen consumption and energy expenditure levels across all intensity levels in persons with SCI compared to individuals without SCI. By employing population-specific METs and the recommended 150-300 min/week of moderate-intensity PA, individuals with SCI would expend approximately 425.3-1672.9 kcal/week, whereas individuals without SCI are estimated to expend 551.3-2168.3 kcal/week (Table 3). When applying 75-150 min/week of vigorous-intensity PA recommendations, persons with and without SCI would expend about 425.3-850.5 and 551.3-1102.5 kcal/week, respectively (Table 3).Weekly volume (kcal/week) in theoretical gender (male)- and weight (70 kg)-matched individuals with and without a spinal cord injury (SCI) based on volume physical activity guidelines [1,6-9]1 L of oxygen is equivalent to 5 kcal [4,5].The above values allow for estimating the duration required to expend 2000 kcal, as Donnelly et al.[90] recommended, and the timeframe needed to achieve a one-pound reduction in body weight (assuming 3500 kcal/pound). When performing 150-300 min of weekly moderate-intensity PA, individuals with and without SCI would need 1.2-4.7 weeks and 0.9 (6 days)-3.6 weeks, respectively, to expend 2000 kcal, as reported by Donnelly et al.[90]. To achieve a one-pound reduction in body weight at this volume, persons with SCI require 2.1-8.2 weeks compared to the 1.6-6.4 weeks needed by individuals without SCI. At 75-150 min/week of vigorous-intensity PA, to expend 2000 kcal, individuals with SCI require 2.4-4.7 weeks, while persons without SCI require 1.8-3.6. A one-pound body weight loss at this volume would require persons with SCI to spend 4.1-8.2 weeks compared to the 3.2-6.4 weeks needed by individuals without SCI engaging in PA. Collectively, independent of the intensity level, individuals with SCI require approximately 23% more time under current PA guidelines to expend 2000 kcal or accomplish a one-pound reduction in body weight compared to those without SCI.PA contributes to an increase in energy expenditure during activity. However, there is also a sustained elevation in energy expenditure that does not immediately return to the preactivity level after PA. This phenomenon is called excess postexercise oxygen consumption (EPOC) [98]. EPOC has been estimated at approximately 15% of the increment in energy expenditure during the exertion [99,100] and can be elevated up to days following PA/exercise [100]. In individuals with SCI, few studies have reported an extended elevation in EPOC [101,102], suggesting EPOC's magnitude is insufficient to produce cardiometabolic benefits after SCI [103]. Furthermore, during the EPOC, there is an increased reliance on lipid oxidation compared to glucose oxidation observed during exercise. The impact of physical activity on lipids as a fuel source is noteworthy since lipid storage in body fat is associated with CMR factors after SCI, independent of activity and fitness levels [104]. Collectively, these findings underscore the necessity of an increase in PA duration and intensity to achieve significant reductions in CMR factors, particularly regarding exercise energy expenditure aimed at mitigating obesity.Because the current evidence highlights the necessity of attaining a minimum intensity level exceeding 6 METs to elicit cardiometabolic health benefits [46-52], the necessity for a prolonged duration of PA to impact obesity [90], and a dose-response relationship in mitigating cardiovascular risk [68,69], it may warrant consideration for other populations. Addressing obesity requires an advanced duration of PA to facilitate weight loss and enhance weight maintenance and prevention [90]. Therefore, individuals with SCI should prioritize engaging in or approaching vigorous-intensity PA for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Table 4 provides a compilation of expected activity-related energy expenditures and durations required for various exercise modalities and injury levels. This compilation utilizes injury level-specific oxygen consumption data from published studies [25,83,105-109], offering guidance to healthcare and fitness professionals in prescribing suitable PA regimens for SCI to reduce CMR.Activity energy expenditure and duration for a given modality at injury-specific oxygen consumptions1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-62.2. Stucki G, Bickenbach J, Gutenbrunner C, Melvin J. Rehabilitation: The health strategy of the 21st century. J Rehabil Med. 2018;50(4):309-16.3. Integrated care for older people (icope): Guidance for person-centred assessment and pathways in primary care. Geneva2019.4. Liguori G, Feito Y, Fountaine C, Roy B. ACSM's guidelines for exercise testing and prescription. Eleventh edition. American College of Sports Medicine's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer; 2021.5. Jacobs PL, Mahoney ET, Nash MS, Green BA. Circuit resistance training in persons with complete paraplegia. J Rehabil Res Dev. 2002;39(1):21-8.6. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity guidelines for americans. JAMA. 2018;320(19):2020-8.7. Oppert JM, Bellicha A, van Baak MA, et al. Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European association for the study of obesity physical activity working group. Obes Rev. 2021;22 Suppl 4(Suppl 4):e13273.8. Carty C, van der Ploeg HP, Biddle SJH, et al. The first global physical activity and sedentary behavior guidelines for people living with disability. J Phys Act Health. 2021;18(1):86-93.9. Nash MS, Groah SL, Gater DR, et al. Identification and management of cardiometabolic risk after spinal cord injury. J Spinal Cord Med. 2019;42(5):643-77.10. Donnelly JE, Blair SN, Jakicic JM, et al. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc. 2009;41(2):459-71.11. Haisma JA, van der Woude LH, Stam HJ, et al. Physical capacity in wheelchair-dependent persons with a spinal cord injury: A critical review of the literature. Spinal Cord. 2006;44(11):642-52.12. Hettinga DM, Andrews BJ. Oxygen consumption during functional electrical stimulation-assisted exercise in persons with spinal cord injury: Implications for fitness and health. Sports Med. 2008;38(10):825-38.13. Nash MS, Bilsker MS, Kearney HM, et al. Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons. Paraplegia. 1995;33(2):80-9.14. Deley G, Denuziller J, Babault N. Functional electrical stimulation: Cardiorespiratory adaptations and applications for training in paraplegia. Sports Med. 2015;45(1):71-82.15. Figoni SF, Dolbow DR, Crawford EC, et al. Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review. J Spinal Cord Med. 2021;44(5):690-703.16. McMillan DW, Kressler J, Jacobs KA, Nash MS. Substrate metabolism during recovery from circuit resistance exercise in persons with spinal cord injury. Eur J Appl Physiol. 2021;121(6):1631-40.17. Farkas GJ, Sneij A, McMillan DW, et al. Energy expenditure and nutrient intake after spinal cord injury: A comprehensive review and practical recommendations. Br J Nutr. 2021;128(5):863-87.Adhering to these proposed intensity and duration prescriptions for PA may effectively address excess body weight and other contributing factors of CMS risk, thereby enhancing CMR outcomes in individuals with SCI. Future research is needed to test the feasibility, safety, and efficacy of this proposed PA prescription and its impact on CMR.Research indicates that a greater volume of PA provides significantly greater health benefits. This suggests that after SCI, a "more is better" approach is advantageous regarding the amount of PA needed for CMR reduction. Individuals with SCI face heightened CMR due to the physiological changes induced by the injury. Diminished physiological responses to PA pose challenges in addressing CMR, especially obesity. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/week. At the same time, those unable to reach such intensities should engage in longer durations of at least 250-300 min/week at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their individual abilities. Given the potential to decrease CMR and the demonstrated efficacy in weight loss and maintenance, increasing PA intensity and duration merit testing in clinical trials and careful consideration in future PA directives. We pay tribute to the legacy of Dr David R. Gater, Jr., M.D., Ph.D., M.S., whose pioneering efforts in understanding and treating neurogenic obesity and metabolic dysfunction following spinal cord injury have profoundly influenced the landscape of SCI rehabilitation as we know it today.