The Thermoregulatory Responses To Palm Cooling During Intermittent And Continuous Exercises In Endurance Athletes

The effects of palm cooling on thermoregulatory parameters like body fluid losses have not been quantified and the value of palm cooling during high intensity intermittent exercise is not known. PURPOSE: To examine the effects of palm cooling on the thermoregulatory responses to continuous and intermittent exercises in well trained endurance athletes. METHODS: Twenty endurance trained athletes were recruited to participate in 2 baseline, 4 randomized experimental and 1 post-intervention visit. Participants performed continuous (30 min at lactate threshold) and intermittent (10 high intensity intervals - 2 min on/2 min off) exercise conditions with and without palm cooling. Palm cooling was applied during the entire continuous exercises and during the rest intervals for the intermittent exercises. Core/skin temperatures, sweat loss, intravascular volumes, plasma osmolality, and metabolic/cardiorespiratory parameters were measured. Values were reported as mean difference [95% CI] of the change scores between palm cooling and control while significance was set at p < 0.05. RESULTS: During continuous exercise, palm cooling resulted in significantly lower core temperature (-0.26 °C [-0.41 to -0.12]), finger skin temperature (-12.2 °C [-14.71 to -9.77], sweat loss (-70.2 mL [-104.3 to -36.0]), HR (-3.9 bpm [-6.1 to -1.8]), VE (-3.2 L/min [-5.5 to -0.8]), VO2 (-97.4 mLO2/min [-121.7 to -73.0]) and EE (-0.49 kcal/min [-0.62 to -0.36]). During intermittent exercise, palm cooling resulted in significantly lower core temperature (-0.25 °C [-0.34 to -0.17]), finger skin temperature (-7.20 °C [-9.12 to -5.29]), sweat loss (-113.4 mL [-197.7 to -29.2]) and HR (-4.4 bpm [-4.9 to -3.3]). For both continuous and intermittent exercises, there were no significant differences for the observed changes in plasma volume and osmolality. CONCLUSIONS: Palm cooling is a potential strategy to mitigate the rise in core temperature and decrease thermoregulatory responses during continuous and intermittent exercise resulting in improved fluid balance. In addition, since the exercise changes in plasma volume and osmolality were not affected by cooling, these parameters might not be ideal markers for examining hydration status during exercise intensities at and above lactate threshold. Supported by Pac-12 SAHWBGP 1554240