Metabolic Acclimation to Cold in Man

¹ From the Institute of Zoophysiology, University of Oslo, Blindern, Norway, the Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania and the Royal Norwegian Air Force Institute of Aviation Medicine and Navy Medical Office, Oslo, Norway

In the months of September and October eight men lived in the Norwegian mountains above tree line in essentially summer clothing and with insufficient night protection. Snow and sleet were common and night temperatures were usually around 3–5°C. The men had enough food and kept busy hiking, fishing and hunting, but deliberately subjected themselves to a great deal of cold stress. At night they undressed and slept in a single blanket bag with a hydrophobic cover. After 6 weeks in the field they had acquired a considerable acclimation to the cold stress. They slept well and maintained a warm surface all night. During rest their heat production remained on an average 50–55% higher than the basal rate before the acclimation. Most of the men developed a slight rise in the BMR. Shivering, visible or detectable by electromyography, occurred frequently during sleep. Control subjects on an average mobilized less extra heat, and were unable to rest and sleep, due to chilling of the periphery, especially the feet. In the acclimated men, therefore, an increased heat production alleviated the shell cooling from which the unacclimated men suffered. When bicycling naked in the cold, just enough to maintain the rectal temperature, the cold acclimated men used as much oxygen as the controls, so neither during exercise nor during rest did acclimation result in increased insulation by shell cooling. The metabolic acclimation to cold found in man agrees with data obtained on other homeotherms.

Note:
with the assistance of H. Andersen, P. S. Enger, E. Hemmingsen, J. Krog, J. Steen and H. Sæther.

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