Analysis of factors concerned in maintaining energy balance for dressed men in extreme cold; effects of activity on the protective value and comfort of an Arctic uniform.

It has been shown that a large fraction of the sweat produced by heavily clothed men during work in the cold remains in the clothing and is relatively ineffective for skin cooling (Belding, Russell, Darling and Folk, 1947). For example, when a man walked at 3.5 miles per hour up a 6.5 per cent grade at OOF. sweat was secreted at a rate of about 500 grams per hour, of which 400 were held in the clothing. It was calculated that the net sweat effective for evaporative cooling of the skin was 230 grams per hour, which included the 100 grams that escaped to the environment, plus 130 grams, the calculated effective equivalent of the 400 grams taken up by the clothing. However, despite this low efficiency of cooling per gram of sweat it was concluded that sweating could be a quantitatively important mechanism for heat dissipation; in this example efficiency of cooling by sweat was only 46 per cent, yet 23 per cent of the energy produced by the man was dissipated by this avenue. One purpose of the present investigation was to determine at various levels of activity not only what fraction of the total energy produced was lost through sweating, but also the part played by the other avenues of energy loss, namely, by convection and radiation from the skin, by warming the inspired air and vaporizing the water in the lungs, and by performing the work of lifting the body. Such information could then be used for evaluating the thermal protection provided by heavy clothing and for revealing factors which may limit itis usefulness. Another purpose was to assess the part played by a suit of Arctic clothing as a thermal barrier under various circumstances of use and to evolve a method of predicting under what conditions this clothing would provide thermal comfort. Most earlier studies of thermal exchanges of clothed men have been concerned with effects of light clothing on heat exchanges during moderate activity or while resting. One stimulus for those studies came from the air-conditioning