Temperatures of skin, subcutaneous tissue, muscle and core in resting men in cold, comfortable and hot conditions

To examine the core-shell model of temperature distribution and the possible role of subcutaneous temperature in heat regulation, comprehensive temperature measurements were made on six nude resting men exposed for 2-3 h to comfort (27 degrees C), cold (15 degrees C) and heat (45 degrees C). Cold produced strong shivering and heat caused heavy sweating. Temperatures were recorded every 10 min from: esophagus, rectum and auditory canal; back muscle and thigh muscle at 20 mm and 40 mm depths; 6 subcutaneous sites; and 16 skin sites. Average temperatures at these 29 sites were tabulated at the ends of comfort, hot and cold and the onsets of sweating and shivering. Body temperature changes were slow to develop, the skin temperatures being fastest, and successively deeper tissues progressively slower. There was occasional after-drop and after-rise. The data were consistent with the core-shell concept. The temperature gradient from subcutaneous tissue to skin, which differed substantially with comfort, the onset of shivering and the onset of sweating, could serve as a regulatory signal. The data are now in computer format and may be of interest to biothermal modelers.