Thermal responses in the body during snowmobile driving.

Thermal responses were examined in 12 healthy men during snowmobile driving (tests for 1 1/2-2 1/2 hours) in mild winter conditions. Ambient temperature ranged from -1 to -13 degrees C and average wind chill index from 1,050 to 1,520 kcal*m2/h. The subjects (23-49 years old) wore their ordinary winter clothing (insulation 1.7 - 2.4 clo). Work rate during the driving was 280-350 W. Rectal temperature increased slightly during driving, and mean skin temperature decreased quickly and fluctuated afterwards at a level 2-3 degrees C lower. Mean body temperature decreased by 1.2 degrees C in the most extreme case. Local cooling on the face and on the peripheral area of the extremities was considered the most serious problem: those temperatures were often below the limit of performance degradation and indicated occasionally the risk of frostbite. The winter conditions were mild in the present study, and on colder days cooling problems will be more severe, as the high incidence of frost injuries reported earlier indicates.