Prediction of Human Heat Tolerance,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MASS
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Human tolerance to heat exposure is limited by body heat storage, as the body is unable to eliminate all the heat it produces andor receives from the environment, and by the physiologic consequencies of such storage. Heat storage of about 80 kcal represents the voluntary heat tolerance limit at which an average, fit, 170 kg man usually decides he is not willing to work much longer in the heat and increase of 160 kcal in his heat content is associated with a 50 risk of heat exhaustion collapse. As the difference between skin and air temperatures decreases, a demand for evaporative cooling in the heat is imposed by the interplay of 3 factors a the metabolic heat production b the effective solar heat load and c the radiative and convective heat exchange through the clothing insulation. This demand may be greater than the maximum evaporative cooling allowed by 3 other factors a the bodys maximum sustainable sweat production about 1Lhr approximately to 675 Watts of cooling power b the limit to sweat evaporation imposed by clothing moisture permeability and thickness and c the difference between the vapor pressure of sweat at the skin surface and the ambient vapor pressure.
- Stress Physiology