Shivering, Oxygen Consumption and Body Temperatures in Acute Exposure of Men to Two Different Cold Environments

¹ From the Department of Physiology and the Cardiovascular Laboratory, State University of Iowa College of Medicine, Iowa City, Iowa

Skin and rectal temperatures, oxygen consumption, respiratory minute volume, carbon dioxide production, respiratory quotient and shivering were recorded in 11 experiments on 9 nude male adults before, during and after sudden exposure to a 10°C environment. The results are compared statistically with those of experiments in an ambient temperature of –3°C. In the 10°C environment the first tremors of shivering appeared in 6.43 minutes and generalized shivering in 10.25 minutes. These times were significantly longer than those observed in the –3°C environment. However, the average mean skin and mean body temperatures of the two groups of subjects were not significantly different at the time the first tremors of shivering and generalized shivering commenced, suggesting that the temperature receptors may sense absolute temperature as well as responding to rate of change. The respiratory minute volume, oxygen consumption and respiratory quotient showed significant increases as a result of the exposure to 10°C and shivering. From a consideration of the data on the ventilation equivalent and the percentage of carbon dioxide in expired air, it is suggested that the rise in respiratory quotient observed in both ambient temperatures was a true increase and not due entirely to over ventilation on the part of the subjects. It was estimated that in the 10°C environment shivering was approximately 5.9% efficient in protecting the body against total heat loss. This was significantly reduced below the value of 11.6% observed at –3°C. It appeared, therefore, that shivering afforded relatively greater partial protection to the total body heat content in the colder environment.