The role of shivering thermogenesis and total body insulation in core cooling rate.

Rectal temperature cooling rate (Tre) is a consequence of an imbalance between heat production and heat loss mechanisms. However, Tre is often related to body insulation, as determined by the thickness of the subcutaneous fat layer, without consideration of the contribution of shivering thermogenesis. The present study investigated the combined effects of insulation and heat production on Tre during cold water (10°and 20°C immersion. It is concluded that relating core temperature cooling rate simply to the insulative adipose layer is inadequate. On the basis of the present results, it is suggested that the following variables be taken into account when attempting to model cooling rate of immersed individuals : 1) The rate of heat production. 2) The insulation provided by the adipose layer. In addition, other tissues may contribute to the overall body insulation. During prolonged immersion total body insulation may vary and will also be affected by the level of peripheral perfusion. 3) The rate of storage of body heat will depend on body composition. It may be insufficient to assume identical specific heat of the body for a range of body types, when determining total body insulation.

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