The Studies on Cold Tolerance in Subtropical and Temperate Natives

This experiment with the intention of investigating differences in cold resistance between those who grew in the subtropical zone and are now living in the temperate zone and those who grew in the temperate zone has been performed in Nagasaki for 4 years; twice (summer and winter) a year. All the subjects were young males: 13 subjects who grew in the temperate zone of Japan (Group M), 11 who grew in Okinawa (Group 0) and 17 who grew in Taiwan (Group T); some subjects of Group 0 and T are those who have lived in the temperate zone of Japan for 6 years. Physical measurement was made on these subjects and then these subjects, in clothes of 1, 8 do, were exposed to cold air for 60 min under the following conditions: room temperature of 10°C, relative humidity of 70 - 80% and wind velocity of 0.5/sec. Skin temperature was continuously measured for 60 min along the exposure to cold air through thermistors attached on 9 spots on the skin, The Douglassbag method was employed for the metabolic measurement; the measurement was made 2 times along the exposure to cold air: 0 min and 60 min from the beginning. Blood samples were also taken both at the beginning and the end of the exposure; measurement was made on haematocrit and free fatty acid (FFA). The following are differences in physique and in response to the exposure to cold air among these three groups. Physique: subjects of Gfoup T were taller and weighed lighter than those of the other groups but had the thickest subcutaneous fat; these results are opposite to the current leading theory that those who have grown in the tropical zone have less subcutaneous fat.Cold resistance: Group M> Group O> Group T; this is the result calculated from the comparative data of distribution on the correlation diagram, that is ?φT: ?φM (decrease in mean skin temperature: metabolic increase), which was designed by the author. With this method, a comparison of cold resistance was made, for each Groups O and T, between those who have long lived in the temperate zone and those who have just come from the subtropical zone: no significant differences were observed for each group. These three groups had differences in correlation between increases in FFA and decreases in RQ, which indicate increases in the fat-combustion quotient: positive corelation was observed for Group O and no correlation for Group M; as for Group T, positive correlation was observed for Group O and no correlation for Group M; as for Group T, positive correlation was observed only for data in winter. The hemoconcentration was calculated through changes in haematocrit as follows:Group T> Group O > Group M.