The Effect of Exercise and Chills on Heat Loss from the Nude Body

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Abstract
Two naked normal men were studied in the Sage respiration calorimeter at temperatures which produced chills after 2 to 3 hours exposure. Six observations were made on involuntary chills and six on voluntary exercise. There was no essential difference between chills and exercise in regard to radiation, convection, vaporization, surface temperature and rectal temperature. When chills were imminent voluntary exercise would check them. When naked men lie motionless in a calorimeter at 22°C. to 25°C. the rectal temperature falls 0.2°C. to 0.5°C. in 2 or 3 hours, but the average surface temperature falls about 3°C. and the man shivers. This exercise usually but not always causes a slight rise in average surface temperature and warms him enough to stave off a second chill for an hour or so. The shivering may store 20 to 40 calories in the body. At temperatures about 27°C. when the men are comfortable, exercise causes a marked increase in the percentage of heat loss by vaporization. At lower temperatures chills and exercise cause little or no change in this percentage. The total amount of radiation diminishes slightly on account of the falling skin temperature, and the percentage of heat lost by radiation decreases markedly. Convection is greatly increased by the movement of the extremities in chills and exercise. This is one manner in which the body may give off more heat through a cool skin than through a warm skin. The metabolism in these two men remained at its basal level until 5 to 10 minutes before the onset of the chills, casting doubt on Rubner's ‘chemical regulation.’ It fell to basal levels promptly after the chills and after moderate exercise. Two athletes after playing squash racquets violently for 36 minutes showed rectal temperatures of 39°C. with falls in average surface temperature of about 3°C. After resting 40 minutes rectal and surface temperatures returned to their former levels. Radiation and convection were changed but little. Increased vaporization dissipated the large amount of heat stored in the body. Here by a different mechanism the body again gave off more heat through a cool skin than through the warmer and drier skin of the basal periods. The chills of malaria are contrasted with the chills due to cold and with the fever due to hard exercise.