Heat and cold responses in prepubertal boys, older men and young women.

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To examine heat loss effector function of prepubertal boys, older men and young women, their heat and cold response during a series of eight experiments were compared with the responses of young men. 1) The results of the 1ィイD1stィエD1experiment suggest that in older men the lower thigh sweating rate observed during the latter half of the 60-min heat test was possibly due to age-related modifications of peripheral mechanisms. 2)The results of the 2ィイD1ndィエD1 experiment suggest that heat tolerance and its improvement with acclimation are little impaired not only in highly fit older but also normally fit older men, when the subjects exercised at the same relative exercise intensity. 3)The results of the 3ィイD1rdィエD1 experiment indicate that the greater skin blood flow observed on the trunk in the boys may be due to a greater withdrawal of vasoconstrictor tone and a greater active vasodilation. 4)The results of the 4ィイD1thィエD1 experiment demonstrate that there are regional differences in both young and old men. 5)The results of skin blood flow(LDI) measurement on chest and thigh(6.25cmィイD12ィエD1by use of a Laser Doppler Imager, support our decrement may proceed from the lower limbs to the upper body. 6)The results of the 6ィイD1thィエD1 experiment suggest that women depend more than men on dry heat loss by greater cutaneous vasodilation(especially on the thigh)rather than wet heat loss by sweating. 7)The results of the 7ィイD1thィエD1 experiment demonstrate that the coldinduced vasodilation in the prepubertal boys and older men was weaker than that in the young men. 8)The results of the 8ィイD1thィエD1 experiment suggest that cutaneous vasoconstriction function decreased over 8 years in healthy active men in their sixth and seventh decades. Although the decreased function was compensated partly by the increase of metabolic heat production, aging led to a decreased ability to maintain core temperature.