Abstract
The effect of local temperature on skin temperature and blood flow are intimately related to internal body temperature or to body thermal state (1). A significant circadian change in internal body temparature occurs with the lower period early in the morning, the rise to a peak occurrin gduring the day. These tests were conducted to determine if the circadian shift in internal temperature alters the response to a step change in temperature.
Methods. The subjects were seated in a calorimeter (2). Heat loss and heat production were measured in a manner already described (2). Body and skin temperatures were recorded with thermistors (YSI thermal underwear suit). Peripheral blood flow was estimated from te change in volume per beat determined by Whitney mercury in rubber guages (3) Measurements were made on 4 subjects over a time period of 3 hours. Experiments were initiated at 0630 with the subject basal and at 1330 with a controlled intake at 1200. An initial period of 90 minutes at 30°C was followed by a period of 60 minutes at 25°C. The 5°C temperature shift was accomploshed in one minute.
The data recorded from these tests, Tables I, II and III, have been analyzed in several ways and 3 salient features appear. First there is a difference in the initial skin and rectal temperatures upon which the step change is imposed, secondly the pattern and extent of the change is similar and finally in the sitting position the toe response is different from that of finger and mean body skin.
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