Inhibition of shivering in man by thermal stimulation of the facial area

Abstract

The contribution of the facial thermoreceptors to thermoregulatory shivering was studied. Seven subjects were exposed to -3 degrees C ambient air for 1 h. Radiant heat was applied to the facial area during 30 s periods at 10 min intervals and the effects on the integrated electromyographic activity (IEMG) in the brachial biceps, trapezius and femoral rectus muscles, and on the heart rate (HR) were studied. During cold-air exposure mean skin temperature as measured at four sites decreased by 15.5 +/- 0.6 degrees C (mean +/- SE) while rectal temperature remained virtually unchanged. During the radiant heat exposures IEMG activity decreased by 18.9 +/- 2.3%; HR decreased by 11 +/- 1 beats min-1. The changes in IEMG occurred within or slightly below the range of maximum cold receptor sensitivity (20-30 degrees C) and coincided with the maximum rate of change in chin temperature. The observed inhibition of shivering IEMG during locally applied facial heat stimulation suggest that the trigeminal region contributes an important input to the overall thermoregulatory responses.