Effect of acclimatization on the sweat rate-rectal temperature relationship.

Abstract

A sample of 13 acclimatized Bantu males and a fresh sample of between 6 and 10 unaccltmatized Bantu at each heat stress condition (making a total of 353 unacclimatized Bantu) were exposed to 45 different combinations of air temperature (with the air saturated with water vapor), wind velocity, and work rate. A table was constructed of the mean sweat rate for 0.3[degree]F class intervals of rectal temperature. The mean sweat rates were based on different sample sizes in the various class intervals of rectal temperature. An exponential equation of the form Y = K(I - ae-bxm) was used to express the relationship and the curves so derived fitted the data very well indeed. Comparison of the curve for the acclimatized and unacclimatized men showed that they were significantly different (at the 5% level) and that in the acclimatized men: the origin of the steep part of the curve is shifted by over 1[degree]F to the left; the steepness of the slope of the curve is increased; and the asymptote, or maximum value, of sweat rate is higher. From these results it can be concluded that there is an increase in "sensitivity" and an increase in "capacity" of the regulation of sweat rate by the temperature of the hypothalamus (as represented by the rectal temperature).