Fall in skin temperature of exercising man.

Fall in skin temperature during initial muscular work was investigated in ten healthy men. Bicycle exercise was performed at workloads of 50-150 W in a climatic chamber at ambient temperatures of 10-40 degrees C (relative humidity 45-55%). Skin temperatures at seven or eight points over the body surface were measured using thermography and thermocouple recording systems. Sweat rates were significantly higher at 40 degrees C than at 30 degrees C, whereas the fall in skin temperature was almost equal. The reduction of skin temperature during exercise was the same throughout the year, although sweat rate was significantly higher in summer than in winter. In coloured thermographics of the skin temperature distribution during exercise of both 50 and 150 W at 10 or 20 degrees C, the skin temperature began to decline immediately at the onset of the exercise. Increased work intensities reduced skin temperature. The results suggest that fall in skin temperature during initial exercise was not due to increased evaporative cooling but to vasoconstriction, probably caused by non-thermal factors.