ACCLIMATIZATION TO EXTREME COLD

Abstract

Metabolic observations were made on 5 subjects who tesided continuously for 3 days in a comfortable environment, 25 [degree]C, for 8 days in a cold environment, [long dash] 29 [degree]C, and for another 3-day period at 25 [degree]C. No changes in basal values for heart rate or rectal temperature occurred. The caloric expenditures during quiet sitting and while performing a standard amt. of work were higher during exposure to the low ambient temperature. The duration of exposure to low temps, did not markedly influence the energy output during the sitting period for 4 of the 5 subjects. The 5th individual, who was breathing air of approx. 20[degree]C during this time, showed a striking decrease in caloric output with increased exposure. The significance of this finding and its association with a higher level of toe temperature is discussed. Four of the subjects exhibited an increased metabolic rate[long dash]-an afterstimulating effect of cold[long dash]on their return to the control environment. This was not observed in the 5th subject, the individual mentioned above. The energy requirements for the standard work on a treadmill at 3.0 mph and a 3.3% grade were increased during low temp, exposure. A small but definite return towards normal values occurred with continued exposure, but its relation to the development of a state of acclimatization was not clear. The decrease could be explained adequately on the participation of a num- ber of other factors. There is some indication from the data that acclimatization to cold may occur, but at the present the evidence is too equivocal for a definite statement.