Seasonal adaptation of thermal and metabolic responses in men wearing different clothing at 10 degrees C.

Thermoregulatory responses at ambient temperatures of 20 and 10 degrees C in six male subjects wearing two different kinds of clothing were compared between summer and winter. The two different kinds of clothing were one insulating the upper half of the body lightly and the lower half of the body heavily (clothing A, the weight in the upper and lower halves of the body being, respectively, 489 g and 1278 g) and the other insulating the upper half of the body heavily and the lower half of the body lightly (clothing B: 1212 g and 559 g). The major findings are summarized as follow. (i) Rectal temperature was kept significantly higher in clothing B than in clothing A both in summer and winter. (ii) The fall of rectal temperature was significantly greater in summer than in winter in both types of clothing. (iii) Mean skin temperatures and skin temperatures in the face, chest, thigh and leg were significantly lower at Ta of 10 degrees C in summer than in winter in clothing A, while skin temperatures in the face and thigh were also significantly lower at Ta of 10 degrees C in summer than in winter in clothing B. (iv) Metabolic heat production was higher in summer than in winter at 20 and 10 degrees C in both types of clothing. (v) The subjects felt cooler and colder to Ta of 10 degrees C in summer than in winter in both types of clothing. These different responses occurring between summer and winter are discussed mainly in terms of total conductance and dry heat loss.