The aim of the present study was to investigate the effect of wearing a cooling jacket on thermoregulatory responses and endurance exercise performance in a warm environment. Nine untrained male subjects cycled for 60 minutes at 60% VO2max (Ex1) and then immediately exercised to exhaustion at 80% VO2max (Ex2) in 32.0 +/- 0.28C and 70-80% relative humidity. Four separate conditions were set during exercise: no water intake (NW), water intake (W), wearing a cooling jacket (C) and the combination of C and W (C1W). Rectal temperatures (Tre) before Ex1 were not different between the 4 conditions, whereas at the end of Ex1 Tre of C1W was significantly lower than the C and W (p < 0.05). Mean skin temperature (Tsk) was significantly lower in C and C1W than the NW and W during Ex1. Heart rate of C and C1W were significantly lower than the NW and W, and rating of perceived exertion (RPE) in C1W was lower than in the other conditions. Exercise time to exhaustion was significantly longer in C1W than in the other conditions (NW < W, C < C1W; p < 0.05), whereas Tre at exhaustion was not different. Our results indicate that the combination of wearing a cooling jacket and water intake enhances exercise endurance performance in a warm environment because of a widened temperature margin before the critical limiting temperature is reached and also because of decreased thermoregulatory and cardiovascular strain.
(C) 2005 National Strength and Conditioning Association