Exercise Performance In Sport-related Concussion Is Not Limited By Peripheral Cardiovascular Function

PURPOSE: Exercise intolerance is a hallmark of sport-related concussion (SRC) and there is growing evidence for using aerobic exercise to treat concussed adolescents. It is not known if the limitation to exercise performance after concussion is central (i.e., altered cerebral blood flow regulation) or peripheral (i.e., cardiovascular limitation of oxygen delivery to muscles). We examined aspects of pulmonary, cardiac and vascular function during cycle exercise in concussed adolescents within days of injury and again upon clinical recovery. METHODS: 26 concussed adolescents (age 15.42 ± 1.1.4 y, 46.5% female) presenting within 10 days of concussion and 24 age and sex matched healthy controls (age 15.83 ± 1.55 y, 41.7% female) were included. Concussed participants completed the Buffalo Concussion Bike Test (BCBT) within 1 week of injury and once after clinical recovery. Controls completed the test twice, 4-6 weeks apart. Respiratory and cardiovascular measures were recorded each minute during the BCBT. RESULTS: Heart rate (146.90 vs 144.89 bpm), stroke volume (115.25 vs 108.13 cm3), cardiac output (16.57 vs 15.89 L/min), ventilation (0.65 vs 0.61 L/sec), and VO2 (20.24 vs 20.17 L/kg/min) were not significantly different between concussed participants and controls at any time during exercise. There were statistically significant but small, not clinically meaningful, differences in diastolic and systolic blood pressure at various time points between concussed and healthy participants. CONCLUSION: Acutely concussed adolescent athletes did not differ significantly from healthy controls, or after recovery, in their cardiovascular responses to a graded exercise bike test that measured their exercise tolerance after SRC. Importantly, there was no physiological evidence of aerobic deconditioning in the concussed athletes within 10 days of their injury. The data suggest that the reduced exercise performance (i.e., exercise intolerance) of concussed adolescent athletes within 10 days of SRC is not from limited peripheral oxygen delivery to exercising muscles and that concussed athletes are not aerobically deconditioned during the timeframe that early exercise treatment is being prescribed.