A Model of Heat Loss and Thermoregulation for Immersion in Cold Water,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Twenty male subjects 17 to 28 yrs of age exhibiting a range of body weights 60 kg or - Wt or - 95 kg and body fat 7 or - BF or - 23 underwent total immersion while at rest in water between 36 C and 20 C. The time course of mean skin T sub sk and rectal T sub re temperatures as well as surface heat flow was simulated for each individual immersion with the aid of a time dependent system of differential, heat balance equations coupling different body compartments and the epithelium to the water bath. Metabolic heat production for each immersion supplied as functions of T sub re and T sub sk minus 8 of the instantaneous value to account for respiratory losses were used as heat source terms. This formulation permitted the evaluation of internal and external conductances as a function of water temperature. Analysis showed that cardiovascular compensation occurs at higher bath temperatures for small, lean men compared to large, fatter men. It also showed that body size expressed as the ratio of mass to surface area in addition to fat content controls the maximal internal insulation as well as the rate of decline of T sub re.
- Stress Physiology