Heat storage and body temperature during cooling and rewarming.

During calorimetric experiments with forced cooling and rewarming, changes in rectal temperature (Tre) and mean skin temperature (Tsk) allowed calculations of Burton's (1935) weighting coefficient "a", which relates body temperature change to change in mean body temperature (delta Tb). Calculating delta Tb from change in body heat content (delta Hb), which was determined from direct and indirect calorimetry, included individualized values for body specific heat based on body fat content. In five different cooling procedures there were two with cooling by exposure to cold water and three with cooling in a tubing suit; two of the procedures included mild exercise. The delta Hb ranged from -335 to -1600 kJ; rewarming restored body heat content. The mean (SEM) value of "a" in 119 determinations was 0.75 (0.01). This small variability in the coefficient probably came from the large values of delta Hb and from the use of maximal changes in Tsk and Tre, including afterdrop. Change in Tre by itself correlated with delta Tb, but with much variability. In forced body cooling and rewarming, 0.75 (delta Tre) + 0.25 (delta Tsk) gives an accurate estimate of delta Tb, hence change in body heat storage.