The Effect of Heat Acclimation on Hand Cooling Efficacy During Exercise Heat Stress

The Effect of Heat Acclimation on Hand Cooling Efficacy During Exercise Heat Stress Adams EL, Vandermark LW, Pryor JL, Pryor RR, Vanscoy RM, Denegar CR, Huggins RA, Armstrong LE, Casa DJ. Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT. CONTEXT: Heat acclimation (HA) and body cooling during exercise in the heat both help to mitigate the rise in body temperature; however, the effects of HA and hand cooling combined remain unexplored. OBJECTIVE: To determine the separate and combined effects of HA and hand cooling efficacy, during and after exercise in the heat. DESIGN: Randomized, counterbalanced, crossover design. SETTING: Research laboratory. PARTICIPANTS: Seventeen non-HA (NHA) males (mean±SE; age, 23±1y; height, 179.5±1.6cm; mass, 75.30±2.27kg; VO2 max, 54±1.3ml/kg/min) completed 2 pre-HA heat stress tests (HST1 and HST2), 10 days of HA, and 2 post-HA heat stress tests (HST3 and HST4) in an environmental chamber (40°C; 40%RH). INTERVENTION: HST consisted of two 60-min bouts of treadmill exercise (~45% VO2 max, 2%grade) with 10-min of hand cooling or passive rest following each bout. HA sessions consisted of 90-240 min of treadmill or stationary bike exercise at various intensities. MAIN OUTCOME MEASURES: Cooling rate, hand grip strength, hand volume, palm surface area, and physiological and perceptual measures associated with HA. A 3-way (acclimation x cooling x bout) repeated measures ANOVA with Fishers LSD post hoc (α RESULTS: Compared to NHA, once HA, participants experienced a lower rectal temperature (39.21±0.18°C vs. 38.66±0.15°C, p≤0.05) and heart rate (158±5bpm vs.140±5bpm, p0.05). CONCLUSIONS: Hand cooling improved cooling rates, beyond that of passive rest, in NHA conditions, however, no benefits occurred after HA. Passive cooling after HA provided the greatest cooling rate. Key Words: rectal temperature, cooling rate, grip strength, hyperthermia, peripheral coolin