Study on Mechanisms of Heat Acclimatization Due to Thermal Sweating : Comparison of Heat-tolerance between Japanese and Thai Subjects

Abstract: Heat tolerance and sweat response to heat load of tropical subjects in Chiang Mai and temperate subjects in Nagasaki were compared under identical conditions. Male students in Chiang Mai (n=10) and in Nagasaki (n=10) volunteered for this study. The Thai subjects were a little shorter and slightly leaner than the Japanese. Heat load was applied on the legs by immersion into hot water (43•Ž) for 30 min in the room at 26.6•Ž and 33%rh. Sublingual (oral) temperature was measured with a thermistor probe and local sweat rate was measured by the capacitance hygrometer-sweat capsule method. Change in oral temperature, sweat onset time and local sweat volume were compared between Japanese and Thai. Initial oral temperatures (36.76•}0.11•Ž in Japanese, 36.71•}0.23•Ž in Thai) were identical, and no sweat was observed before heat load. Mean sweat onset time (9.3•}2.1 min chest in Japanese, 16.6•}5.6 min chest in Thai) were significantly longer and local sweat volume (10.19•}5.00 mg/cm2, chest in Japanese, 1.39•}0.91 mg/cm2, chest in Thai) was significantly smaller in Thai subjects than Japanese, however, oral temperature (37.18•}0.32•Ž) of Thai subjects was kept slightly lower than oral temperature