Effect of heat acclimatization on artificial and natural cold acclimatization in man

¹ Environmental Medicine Division, U.S. Army Medical Research Laboratory, Fort Knox, Kentucky

The seasonal changes in oxygen consumption, rectal temperature, and skin temperature in response to a 1-hr nude exposure to 14.1 C were measured once monthly in six subjects between October and February. The same measurements were obtained in another group nude exposed 8 hr daily to a chamber temperature of 13.5 C. Shivering decreased as a result of the seasonal and chamber cold exposure (P < 0.01). Heat production also decreased as a result of both types of exposure (P < 0.05) but never decreased to basal values. Skin temperature in the seasonal group exhibited no change, whereas a small fall occurred in the chamber group (P < 0.05). Although no rectal temperature change was demonstrated in the seasonal group, there was a significant fall in the rectal temperature in the chamber group. After the period of chamber and seasonal cold acclimatization, both groups were subjected to 21 days of heat acclimatization followed by another cold-response measurement. In both groups the changes induced by winter exposure and chamber exposure were not influenced by heat exposure. Since previous studies have demonstrated the lack of influence of cold exposure on heat acclimatization, it is concluded that heat and cold acclimatization are not mutually exclusive and can exist simultaneously in man.

Note:
(With the Technical Assistance of D. R. Johnston, F. W. Jacks, and W. Rawlings)