Abstract
Anthropometric measurements, measurements of skin temperatures and rectal temperature at 30°C and measurements of physiological responses to heat were made on 30 young male residents of Okinawa who were born and raised in Okinawa (Group O) and 30 young male residents of Okinawa who were born and raised in main islands of Japan but move to Okinawa less than two years (Group M) in summer. Sweating reaction was examined for 60 min by immersing both legs in stirred water bath of 42°C in room of 30°C and 70 R. H. Group O showed thinner skinfold thickness, slender body shape, higher skin temperature at 30°C, smaller sweat volume with lower Na concentration in sweat, less rise in core temperature, and less increase in heart rate during heat exposure than group M. It is assumed that group O might have superior capacity for nonevaporative heat dissipation and better efficiency of sweating for cooling the body that group M. It is concluded that the acclimatization to heat of subjects in group O, subtropical natives, had advanced further than those in group M, immigrants of temperate natives to subtropical zone, and heat tolerance of the former is superior to that of the latter.
