Effects of heat acclimation on hand cooling efficacy following exercise in the heat

This study examined the separate and combined effects of heat acclimation and hand cooling on post-exercise cooling rates following bouts of exercise in the heat. Seventeen non-heat acclimated (NHA) males (mean +/- SE; age, 23 +/- 1 y; mass, 75.30 +/- 2.27 kg; maximal oxygen consumption [ VO2 max], 54.1 +/- 1.3 ml center dot kg(-1) center dot min(-1)) completed 2 heat stress tests (HST) when NHA, then 10 days of heat acclimation, then 2 HST once heat acclimated (HA) in an environmental chamber (40 degrees C; 40% RH). HSTs were 2 60-min bouts of treadmill exercise (45% VO2 max; 2% grade) each followed by 10 min of hand cooling (C) or no cooling (NC). Heat acclimation sessions were 90-240 min of treadmill or stationary bike exercise (60-80% VO2 max). Repeated measures ANOVA with Fishers LSD post hoc (a < 0.05) identified differences. When NHA, C (0.020 +/- 0.003 degrees C center dot min(-1)) had a greater cooling rate than NC (0.013 +/- 0.003 degrees C center dot min(-1)) (mean difference [95% CI]; 0.007 degrees C [0.001,0.013], P = 0.035). Once HA, C (0.021 +/- 0.002 degrees C center dot min(-1)) was similar to NC (0.025 +/- 0.002 degrees C center dot min(-1)) (0.004 degrees C [- 0.003,0.011], P = 0.216). Hand cooling when HA (0.021 +/- 0.002 degrees C center dot min(-1)) was similar to when NHA (0.020 +/- 0.003 degrees C center dot min(-1)) (P = 0.77). In conclusion, when NHA, C provided greater cooling rates than NC. Once HA, C and NC provided similar cooling rates.