亜熱帯生育者と温帯生育者の暑熱負荷時の生理的反応の比較

抄録

Anthropometric measurements and observation of physiological responses to heat were made in July on 25 young male residents in Okinawa who were born and reared in Okinawa, subtropical zone (group 0) and 23 young male residents in Okinawa born and reared in the Main Islands (temperate zone) but moved to Okinawa in less than three years (group M) . Sweat tests were performed by immersion of both legs up to the knees in a stirred water bath of 42°C in a room of 30°C, 70% relative humidity for 60 min. Subjects in group O were shorter in height, lighter in body weight with a less subcutaneous fat layer than those in group M, and showed greater value of the ratio of body surface area to body weight. Group O showed higher mean skin temperature and less metabolic rate at 30°C than group M. Since higher mean skin temperature indicates greater capacity for non-evaporative heat dissipation, higher skin temperature in addition to less metabolic rate for group O might explain the longer latent period of sweating, a smaller sweat volume and less rise in core temperature in heat. Sweating reaction for subjects in group O was characterized by longer latent period of sweating, lower sweat rate and lower Na concentration in sweat, and was similar to that of tropical natives. Difference in physiological responses to heat between two groups might reflect more advanced heat acclimatization of subjects in group O when compared with those in group M.