Abstract
Anthropometric measurements and measurements of body temperature and latent period for onset of sweating were made in the summer in Okinawa on 7 young male Japanese who were born andreared in Okinawa, subtropical zone (Group O), and 7 young male Japanese who were born and reared in the Main Islands of Japan, temperate zone, but moved to Okinawa in less than three years (Group M). Measurement of numbers of active sweat glands were made on 30 subjects in Group O and 20 subjects in Group M in Nishinomiya.
After staying at rest for 30 min in a room with a temperature of 30 C and 70 per cent R. H., oral temperature and skin temperatures at 10 sites were measured. Sweating was induced by immersing the legs just below the knees and the time of the onset of sweating was determined by measuring the weight of the filter paper mounted on the back which was changed at 2 min intervals. Counting of numbers of the active sweat glands at seven sites was made by the Minor's calorimetric methods after sweating was induced by the foot bath method.
Group O showed a little shorter height, lighter body weight and higher ratio of body surface to body weight than Group M. The skinfold thickness for Group O was thinner than that for Group M. The mean values of oral temperature and skin temperatures for Group O were slightly greater than those for Group M. The mean value of Tor-Ts gradient for Group O was slightly smaller than that for Group M. The mean value of the density of active sweat gland for Group O was greater than that for Group M.These results suggest that the capacity of Group O for non-evaporative heat dissipation is superior to that of Group M, Group O has higher conductive-convective heat transfer coefficient from core to skin than Group M, and the efficiency and capacity of evaporative heat dissipation for Group O are superior to those for Group M.The anthropometrical characteristics, higher skin temperature, higher conductive-convective heat transfer coefficient, longer latent period of sweating reflex, and greater density of the active sweat gland for Group O might be explained as due to a result of long-term heat acclimatization to hot climate.
