In the present study, we examined subjective evaluation and physiological responses to heat stress for the purpose of finding out an effective themoregulatory method to prevent heat stroke and deterioration of work performance during sports activity in a hot environment. Subjects were five healthy male students. They were exposed to a hot environment at the ambient temperature of 37 ℃ and relative humidity of 60 % for 60 minutes. In that environment they rested in sitting position for 10 minutes and performed bicycle exercise for 20 minutes twice separated by a 10 minutes rest interval. In the cold water intake test, they took 250 ml of cooled sports drink (7 ℃) 30 minutes after the beginning of the exposure. In the head cooling test, the forehead and vertex were continuously cooled by the cold water of 10 ℃. In the combination test of water intake and head cooling, subject's forehead was cooled and the 250 ml of sports drink was consumed. During the hot environment exposure, the body temperature and heart rate were increased, suggesting that thermoregulatory mechanism was well functioning. In the no water intake test, the increase in tympanic temperature was the largest, and the perspiration rate was almost twice as much as observed in other conditions. In the water intake test, the increase in rectal temperature could not be suppressed but the increase of mean skin temperature was suppressed. In the head-cooling test, the difference of cooling site did not show any difference in thermoregulatory function. The combination test of water intake and head cooling suppressed the increase in tympanic temperature.

DESCENTE SPORTS SCIENCE Vol.20/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE