STUDY OF THE PHYSIOLOGIC EFFECTS OF COLD

Abstract : Continuous observations were made of the metabolic rate, skin and rectal temperatures of men while dressed in Arctic uniforms and sitting quietly in extremely cold environments. Ambient temperatures ranged from +1.1 to 40C. The heat production in the cold was above basal values during the entire test period. In the -40C environment, average metabolic increase of 13, 53 and 74 per cent were recorded for the first, second and third hours respectively. The rise in heat output during the first hour could not be explained on the basis of shivering. In the third hour, shivering was present in the majority of the subjects. The fall in rectal temperatures was moderate although values of 35. 4C. were occasionally observed. The absolute value was not correlated with the presence of shivering and, therefore, low rectal temperatures could not be considered as the stimulus for shivering. Mean skin temperatures fell precipitously during the first hour of exposure and were stabilized before the end of the test period. Considerable variability was observed in both the rate and extent of fall not only in different men, but in repeat tests on the same subject. Of all the skin areas, the hands and feet exhibited the greatest temperature changes in both rate and degree of fall. Toe temperatures below 0C. were noted in several instances. The susceptibility of the extremities to cold environments was related to their sensitive vasomotor mechanisms and to the fact that they were provided with the least amount of insulative protection.