Thermal responses of 6- to 8-year-old children during immersion of their legs in a hot water bath.

Twenty-three children (12 boys and 11 girls) and 13 female students served as the subjects in summer. The children were from six to eight years old. The subjects were seated in a hot room of 30 degrees C and their legs were immersed in bath water of 42 degrees C for 30 minutes. Total sweat rate, local sweat rate on the back, rectal temperature, skin temperatures at eight sites, heart rate and blood pressure were measured during the experiments. Total sweat rate of both groups was similar, but local sweat rates of the children were significantly smaller than those of the students. Although the degree of increase in rectal temperature from immersion in the hot bath were similar, the increases of heart rate and skin temperatures on the thigh and forearm were greater in children. These results suggest that the thermoregulatory ability of children during heat exposure is similar to that of young female adults. However, it is found that for heat loss, children resort more to vasodilation than sweating during heat exposure as compared to adults. The children were divided into two groups according to whether the children were exposed to air cooling systems in summer in their infancy or not. There was no significant inter-group differences in physiological responses during immersion in the hot water bath. It is found that the ability of Japanese children to tolerate heat was not reduced distinctly by the frequent use of an air cooling system in infancy.