Simultaneous Recruitment of Sweating and Perception of Warmth in Man

¹ From the Department of Physiology, Stritch School of Medicine and the Graduate School of Loyola University, Chicago, Illinois

The nude subject, placed in a climate chamber in which ambient temperature was gradually elevated, first showed active sweating on the dorsum of the foot with progressive recruitment of sweating on successively higher levels of the body. The forehead was the last area to sweat. Simultaneously the sensation of warmth was reported earliest on the forehead, with successive appearance on the lower areas of the body with increasing thermal stress. The subjects did not report a sensation of ‘hot’ on the feet in any of the experiments. Thus, with progressively rising ambient temperature, sweating was recruited first on the distal portions of the lower extremity and last on the face. The appearance of the warmth sensation was precisely the reverse. It therefore appears improbable that the same afferent receptors are concerned with the reflex origin of sweating and with the excitation of the local sensation of warmth. When only the upper portion of the body (from umbilicus upward) was heated in the climate chamber while the lower trunk and extremities remained exposed to a cool environment, sweating was first recruited on the dorsum of the foot. This was true even though skin temperatures of lower extremities were progressively falling. The sensation of warmth was referred to the warmed areas only. When only the lower trunk and extremities were heated in the chamber while the upper portion of the body remained cool, sweating was again first recruited on the distal portion of the extremity. The warm sensation was reported on the feet while sensation on face and upper trunk remained neutral to cool.