沖縄への夏季帰省が沖縄より本土に移住したヒトの耐熱性, 耐寒性および局所耐寒性に及ぼす影響について

Sweating test and peripheral cold tolerance test were performed on 10 young male university students born and raised in Okinawa (the subtropical zone) but moved to the Japanese Main Islands (the temperate zone) within last three years and cold tolerance test was made on five subjects. Two series of experiments were performed in Nishinomiya, using a climatic chamber. The first series of experiments was performed in July before the return of the subjects to Okinawa (the experiment 2). The second series of experiments was performed in September after a month's stay in Okinawa in August (the experiment 1). Sweating reaction was examined on the subjects dressed in shorts only 60 min by immersing both legs in stirring water of 42 C in a room of 30 C with 70% R.H. Cold tolerance test was performed on the subjects clothed with 1.8 clo by taking off a blanket after covering with a blanket in supine position for 20 min in a room of 10 C with 70% R.H. Physiological responses of the subjects to cold were observed for 60 min. Peripheral cold tolerance test was made by dipping the left middle finger with a thermocouple attached to the nail bed into ice water for 30 min and changes of the skin temperature were measured continuously. Greater sweat volume, lower sodium concentration in sweat at the given sweat rate and less rise in oral temperature in the experiment 1 than in the experiment 2 were observed.<BR>These results indicate acclimatization to heat of the subjects was induced by the return to Okinawa in summer and heat tolerance of the subjects was slightly improved when assessed by numetrical heat tolerance index after a month's stay in Okinawa in summer.<BR>In cold tolerance test, significantly greater increase in the metabolic rate, greater frequency of shivering and considerably lower drop of the mean skin temperature in the experiment 1 than in the experiment 2 were observed. These results indicate the ratio of increase in the metabolic rate to thedrop in the mean skin temperature during cold exposure was greater in the experiment 1 than in the experiment 2. Thus it might be said that cold tolerance was reduced by the return to Okinawa in summer and living in a hot and humid climate. The mean value of time for first temperature rise of the vascular reaction of finger in the cold was significantly greater in the experiment 1 than in the experiment 2. The mean value of resistance index of frost bite caluculated by the Nakamura's method was significantly smaller in the experiment 1 than in the experiment 2. It may thus be concluded that the vascular reaction of finger in the cold is depressed and peripheral cold tolerance is reduced after the returnto Okinawa in summer.