Seasonal acclimatization to cold in man

¹ Environmental Medicine Division, US Army Medical Research Laboratory, Fort Knox, Kentucky

Six subjects were measured once monthly from October to February for alterations in shivering, heat production, and rectal and skin temperatures produced by a standard cold exposure of 14.1 ± 0.46°C for 1 hour. The responses of a second group of five subjects were measured once monthly from February to September during a cold exposure of 13.7 ± 0.9°C. In the October-February group, shivering decreased to a January mean value 7% of the October figure (P < 0.01). Cold-induced heat production decreased in February to a value 52% of the October figure (P < 0.05). Mean rectal temperature and mean surface temperature over the total period of study showed no consistently significant change. The decrease in shivering was associated with a change in the surface temperature threshold of shivering onset. The February-September group showed an increase in shivering reaching a maximum in September (P < 0.01). Again consistently significant alteration in surface or rectal temperature could not be demonstrated. The highly significant change in shivering and the less significant change in heat production observed suggests that man seasonally acclimatizes to cold and that this acquired acclimatization is lost during the summer months.

Note:
(With the Technical Assistance of F. C. Bell, W. Rawlings and L. Lee)

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