Thermoregulatory responses of prepubertal boys to heat and cold in relation to physical training

In an attempt to examine the effect of physical training on thermoregulatory responses in prepubertal boys, three series of experiments were performed, in summer. To all the subjects with swimming pants a heat stress was given through a foot bath of 42 degrees C in a hot climate, and a cold stress through exposure to an atmosphere at 20 degrees C Ta and 60% RH. Physical training increased work performance, whereas no significant effects were observed on rectal and mean skin temperatures. Metabolic rate was measured of children exposed alternately to 30-min heat and 30-min cold for 2 hr, and exposed to 60-min heat and 60-min cold separately, respectively. The mean skin temperature increased and decreased more on exposure to heat and cold, respectively, but the metabolic rate increased less remarkably in the children than in the adults. It was postulated thermoregulation might respond less distinctly to physical training in the children than in the adults, and that the decreased effect of training on the children might originate from an undifferentiated thermoregulatory system.