The aim of the present study was to determine the combined effects of pre-cooling and water ingestion on thermoregulatory responses and exercise capacity at 32 degrees C and 80% relative humidity. Nine untrained males exercised for 60 min on a cycle ergometer at 60% maximal oxygen uptake (VO2max) (first exercise bout) under four separate conditions: No Water intake, Pre-cooling, Water ingestion, and a combination of pre-cooling and water ingestion (Combined). To evaluate the efficacy of these conditions on exercise capacity, the participants exercised to exhaustion at 80% VO2max (second exercise bout) following the first exercise bout. Rectal and mean skin temperatures before the first exercise bout in the Pre-cooling and Combined conditions were significantly lower than in the No Water and Water conditions. At the end of the first exercise bout, rectal temperature was lower in the Combined condition (38.5 +/- 0.1 degrees C) than in the other conditions (No Water: 39.1 +/- 0.1 degrees C; Pre-cooling: 38.7 +/- 0.1 degrees C; Water: 38.8 +/- 0.1 degrees C) (P < 0.05). Heat storage was higher following pre-cooling than when there was no pre-cooling (P < 0.05). The final rectal temperature in the second exercise bout was similar between the four conditions (39.1 +/- 0.1 degrees C). However, exercise time to exhaustion was longer (P < 0.05) in the Combined condition than in the other conditions. Total sweat loss was less following pre-cooling than when there was no pre-cooling (P < 0.001). Evaporative sweat loss in the Water and Combined conditions was greater (P < 0.01) than in the No Water and Pre-cooling conditions. Our results suggest that the combination of pre-cooling and water ingestion increases exercise endurance in a hot environment through enhanced heat storage and decreased thermoregulatory and cardiovascular strain.

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Hasegawa, H., T. Takatori, T. Komura, and M. Yamasaki. Wearing a cooling jacket during exercise reduces thermal strain and improves endurance exercise performance in a warm environment. J. Strength Cond. Res. 19(1):122-128. 2005.-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% V O 2 max (Ex1) and then immediately exercised to exhaustion at 80% V O 2 max (Ex2) in 32.0 Ϯ 0.2ЊC 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 (CϩW). Rectal temperatures (T re ) before Ex1 were not different between the 4 conditions, whereas at the end of Ex1 T re of CϩW was significantly lower than the C and W (p Ͻ 0.05). Mean skin temperature (T sk ) was significantly lower in C and CϩW than the NW and W during Ex1. Heart rate of C and CϩW were significantly lower than the NW and W, and rating of perceived exertion (RPE) in CϩW was lower than in the other conditions. Exercise time to exhaustion was significantly longer in CϩW than in the other conditions (NW Ͻ W, C Ͻ CϩW; p Ͻ 0.05), whereas T re 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. KEY WORDS. hot and humid environment, core temperature, skin temperature, body cooling