THERMAL RESPONSES AND EFFICIENCY OF SWEATING WHEN MEN ARE DRESSED IN ARCTIC CLOTHING AND EXPOSED TO EXTREME COLD

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Abstract
Men dressed in Army arctic uniforms were exposed for 2-hr. periods in a cold room at temps. between 40[degree]F and - 40[degree]F while sitting, standing, and walking at various speeds on the level and uphill. Sweat production varied between about 50 and 1800 gs. and in all expts. Most of the sweat secreted was absorbed by the clothing, a larger proportion at the lower temps. When sweating was light or moderate this uptake was confined to the outer layers, but when profuse the underclothing was also wetted. According to an hypothesis formulated to explain the principles governing the transfer of sweat from the skin, the vapor pressure difference between the relatively warm inner layers and the cool outer layers was large. As a result of this, the inner layers did not pick up much moisture unless sweating was profuse. However, since the vapor pressure difference between the cool outer layers and the cold environment was small, much of the sweat secreted accumulated in the outer garments regardless of amt. Sweating was shown to be an inefficient way to achieve body cooling when men were heavily dressed in the cold because the process of recondensation in the clothing returned heat to the skin, the total heat returned being proportional to a ratio obtained by dividing the amt. of insulation outside the point of condensation by the total insulation. The data suggest that when it is possible for men to modify their activity to the point of feeling "cool but comfortable" during exposures to cold, sweating and accumulation of moisture in clothing will be minimal.

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