Basal Heat Production and Elimination of Thirteen Normal Women at Temperatures from 22°C. to 35°C.

Abstract

Seventy-six experiments in the Sage respiration calorimeter were made on 13 normal young women at environmental temperatures between 22°C. and 35°C. The measurements in hourly periods included heat production, respiration quotient, rectal temperature, average surface temperature, total heat loss, conductance and the percentages of heat lost by radiation, convection and vaporization. Careful note was made of muscle tensing, shivering and sensations of cold, warmth and comfort. The average basal metabolism of the 13 women was 31.2 cal. per square meter per hour. This is so much lower than the heat production of men per unit of surface that women have an advantage over men in the warm zones and do not need to sweat as much. In the cold zone some, but not all, women lose heat less rapidly than men. In the cold zone the women lost about 67% of their heat by radiation and this percentage dropped in linear fashion to zero when the calorimeter temperature was the same as skin temperature. Vaporization accounted for only 16–18% of the total loss at the coldest temperatures and reached the conventional figures of 24–25% only at environments of 27°C.–28°C. It is obvious that fixed percentage figures for radiation, convection and vaporization apply to only one strictly specified set of conditions. The comfort or neutral zone for women, naked, and in strict basal conditions, extended from about 26°C. to 30.9°C. In this zone the average skin temperature was 33.9°C. and in the upper part of the zone heat production closely approximated heat elimination. Of the 10 women studied at temperatures of 28 and below, 6 showed an increase in metabolism in the cold greater than the amount that could be ascribed to muscle tension or restlessness. This is evidence that some but not all women are subject to Rubner's “chemical regulation” of metabolism but the amount involved is small. In the cold zone the peripheral tissues lost so much heat that the average temperature of the body dropped 2.8°C. before the onset of shivering. The metabolism of the peripheral tissues falls with lower temperatures. Since the total metabolism remains constant or rises there must be an increase in the metabolism of the core of the body which compensates for the decrease in the periphery. In this sense there is a chemical regulation in men and women.