The purpose of this study was to determine whether young children's thermoregulation during heat exposure varies with age and body size. A total of 34 young children (aged 6 months-8 years)-18 boys and 16 girls-participated in the study. They were divided into five groups according to age (<1 year, 1 year, 2-3 years, 4-5 years, and 8 years). The participants sat for 30 min in a 27°C, 50% rh room, then moved to a 35°C, 70% rh room and remained seated for at least 30 min. They then returned to the first 27°C room and remained stationary for 30 min. Rectal temperature (Tre) and skin temperature (Tsk) were continuously recorded, and the amount of whole-body sweat rate (SR) was measured. Local SR of the back and upper arm were collected with filter paper to calculate local sweating volume, and Na + concentration was measured later. The smaller the age, the significantly greater the increase in Tre. There was no significant difference in the amount of whole-body SR and the increase in Tsk during the heating among the five groups. Furthermore, there was no significant difference in whole-body SR per increase in Tre during heating between the five groups, but a significant difference was found in back local SR per increase in Tre with age. Difference in local SR between upper arm and back was observed at age 2 years and above, and difference in Na+ concentrations in sweat was observed at age 8 years. The development of thermoregulatory responses with growth was observed. The results indicate that the thermoregulatory response is disadvantaged by immature mechanisms and small body size in younger children.
Keywords: Child; Heat exposure; Rectal temperature; Skin temperature; Sweating rate.
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