Individual Difference in Physiological Responses to Cold

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In March when the maxmal seasonal acclimatization to cold induced, five naked Japanese adults were exposed to 10°C for 2 hours. Ten parameters concerning physiological responses to cold were compared each other, and comparisons of these parameters between the subjects were made.Measurements were made of oxygen uptake, mean skin temperature, rectal temperature, electromyogram and electrocardiogram before and during cold exposure. From these data, following parameters were calculated; heat production, increase in heat production, percent increase in heat production, decrease in mean skin temperature, ratio of increase in heat production to decrease in mean skin temperature, skin insulation, initial rise in rectal temperature, change in rectal temperature, initial change in heart rate and change in heart rate.The heat production has a correlation with skin insulation. Parameters calculaled out of heat production correlate with initial rise in rectal temperature, and they generally correspond to shivering patterns shown by electromyography. Parameters relating to heart rate correlate with some of those relating to rectal temperature and to heat production.From a view point of heat balance, heat production, skin insulation and change in rectal temperature or decrease in mean skin temperature were applied to three variables of a two variate multiple regression. Consequently multiple correlation coeficients approximate to 1.000 or are statistically significant. Responses to cold of these four parameters for the five subjects are summarized into three types. The first, owing to large skin insulation, rectal temperature does not fall although heat production is small. The second, due to small skin insulation, rectal temperature finally falls although they produce a considerable amount of heat. The third, in spite of the smallest skin insulation, rectal temperature does not fall because of excessive heat production. Decrease in mean skin temperature is slight for the second type, moderate for the first type and marked for the third type. These different responses to cold among individuals were suggested to form a foundation to elucidate the difference among human groups.