Body temperature during work at different environmental temperatures.

In human subjects it was found that during muscular work only small and unsystematic differences existed between temperatures measured at different depths in the rectum, whereas a steep temperature gradient was found along the upper oesophagus.—The oesophageal temperature measured just above the diaphragm (i. e. close to aorta and left heart) reached during exercise the work level much faster, and, also in the recovery period returned to the resting level much more rapidly than did the rectal temperature. During leg-work the level reached by the oesophageal temperature was considerably lower than that reached by the rectal temperature while during arm-work they were of about the same height. Breathing of air saturated with water vapor at body temperature did not influence the temperature in the lower oesophagus but eliminated the steep temperature gradient in upper oesophagus. Under these conditions the sublingual temperature was equal to the temperature in lower oesophagus. The experiments suggest that the oesophageal temperature measured just above the diaphragm is a good index of the temperature of a large part of the core of the body.—During work both rectal and oesophageal temperatures were practically independent of environmental temperatures between 5 and 30°C.