Sweating of human volunteers immersed to the neck in hot water declined markedly after reaching a peak in the 1st hr of exposure. This decline always occurred in fresh water regardless of level of thermal stress. Sweating in the 3rd hr of exposure was about the same whether the water was hot in the 1st 2 hr (sweat glands active) or cool (sweat glands inactive). Thus “fatigue” was not responsible for the decline. It is suggested that observations of decline of sweating in warm-humid air environments, attributed to “sweat gland fatigue,” in reality may have been owing to soaking of the skin with sweat. The mechanism of suppression appears more complex than blockage of the sweat ducts by swelling of the corneum. Rather, there is an association between the amount of decline and conditions favoring diffusion of water to deeper strata of the skin. For example, adding salt to the water reduced the decline; no decline occurred in 15% NaCl. Submitted on March 6, 1961
Human subjects were transferred between environments imposing different levels of heat stress. Analyses of measurements obtained after a reasonably steady state had been achieved in each of several environments revealed equally good correlation between a) sweat rate and ear temperature (tympanic membrane), and b) sweat rate and calculated deep skin temperature (hypothetical). The correlations are consistent with adjustment of sweating in response to either hypothalamic temperature or temperature of skin receptors or some combination of the two. However, during the first 20 min after transfer, changes in sweat rate and skin temperature occurred together and in the same direction, but were not accompanied by any consistent change in ear temperature. Thus, to the extent that ear temperature represents hypothalamic temperature, an hypothesis of control of sweating based on hypothalamic temperature alone is not tenable. Alternative physiological explanations are given for data developed elsewhere and used in support of an hypothesis of sweat control solely from the hypothalamus. Submitted on August 14, 1961
Acclimatization to heat, repeatedly demonstrated in male subjects, has not been reported in females. This paper presents quantitative evidence for heat acclimatization in women. Nine women participated (five at University of Pittsburgh and four at University of Illinois, Urbana) in daily 2-hr walks in the heat for 2–3 weeks. By the usual criteria (reduced pulse rate, reduced rectal temperature rise, lower skin temperature, ability to complete the assigned task, and subjective comfort) all subjects became acclimatized to heat. Submitted on September 4, 1962
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