Effects of wind on the thermal and metabolic responses to exercise in the cold.

The thermal and metabolic responses to exercise were studied in a cold environment with and without a wind. Six men and two women rode a cycle ergometer for 90 min at 55-60% VO2max in a -20 degrees C environment. Subjects were exposed to a 4.1 m . s-1 wind on two of the four exposures. The subjects wore regulation cross-country ski uniforms. An additional vest was worn on 2 d, 1 d with the wind and 1 d without the wind. Total insulation for the ski uniform (Icl+a) was 1.59 clo and 1.77 clo with the vest. Final Tre, Tsk, and Tb were significantly lower, and radiative and convective heat loss, heat loss from body storage, and tissue insulation (It) were significantly greater when exercising in the wind. The addition of the vest increased only Tsk. Both metabolic rate and heart rate increased significantly during exercise, but no significant differences were observed between wind and no-wind conditions. The subjects responded to the increased cooling effect of the wind by increasing It, however, this response was not sufficient to prevent loss of stored heat and Tre from falling. It was concluded that the exercise intensity must be 10 METS or greater to maintain thermal balance when exercising in a -20 degrees C environment with a 4.1 m . s-1 wind if Icl+a = 1.59 clo.