Metabolic and thermal responses to muscular exertion in the cold

¹ Institute of Work Physiology, Blindern, Oslo, Norway

The metabolic and thermal responses to muscular exertion in the cold were studied in outdoor and indoor workers. The metabolic rate during exercise was the same in the cold as in a thermally neutral (warm) environment when workload was sufficiently high to prevent a fall in the rectal temperature. At lower levels of work the metabolic rate in the cold was higher than that in the warm. No significant differences in the work metabolism were found between the groups. When the resting subjects were exposed to the cold environment prior to the exercise the skin temperature decreased. The rate of decrease diminished as exercise progressed and at higher load of work the extra heat generated in the body was enough to rewarm the skin, even on the most peripheral parts. The rate of decrease of skin surface cooling during rest in the cold was found to be slower in the outdoor workers than in the indoor workers, and the onset of the rewarming occurred much quicker in the former. These differences in skin temperature between outdoor and indoor workers indicate an acclimation to cold affecting the vasomotor control of the skin circulation. The hypothesis is suggested that habituation to cold leads to a lower set point of the thermosensitive cells in the thermoregulating center, so that vasodilatation impulses are discharged at a lower temperature.

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