Effects of metabolic rate on thermal responses at different air velocitiesin-10 degrees C

The effects of exercise intensity on thermoregulatory responses in cold (-1 0 degreesC) in a 0.2 (still air, NoWi), 1.0 (Wil), and 5.0 (Wi5) m s(-1) wi nd were studied. Eight young and healthy men, preconditioned in thermoneutr al (+20 degreesC) environment for 60 min, walked fur 60 min on the treadmil l at 2.5 km/h with different combinations of wind and exercise intensity. E xercise level was adjusted by changing the inclination of the treadmill bet ween 0 degrees (lower exercise intensity, metabolic rare 124 W m(-2), LE) a nd 6 degrees (higher exercise intensity, metabolic rare 195 W m(-2), HE). D ue to exercise increased heat production and circulatory adjustments, the r ectal temperature (T-re), mean skin temperature (T-sk) and mean body temper ature (T-b) were significantly higher at the end of HE in comparison to LE in NoWi and Wil, and T-re and T-b also in Wi5. T-sk and T-b were significan tly decreased by 5.0 m s(-1) wind in comparison to NoWi and Wil. The higher exercise intensity was intense enough to diminish peripheral vasoconstrict ion and consequently the finger skin temperature was significantly higher a t the end of HE in comparison to LE in NoWi and Wi1. Mean heat flux from th e skin was unaffected by the exercise intensity. At LE oxygen consumption ( Vo(2)) was significantly higher in Wi5 than NoWi and Wil. Heart rate was un affected by the wind speed. The results suggest that, with studied exercise intensities, produced without changes in walking speed, the metabolic rate is not so important that it should be taken into consideration in the calc ulation of wind chill index. (C) 2001 Elsevier Science Inc. All rights rese rved.