USE OF DAILY METABOLIC PERIODICITIES AS A MEASURE OF THE ENERGY EXPENDED BY VOLUNTARY ACTIVITY OF MICE

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Abstract
At temperatures of 10, 20, and 30 °C., average metabolism of 12 mice in small respiration chambers was significantly greater during the night than during the day but was sensibly the same at night and day when constant work levels were imposed in a treadmill apparatus. In these tests the increase in metabolism due to work varied only slightly, if at all, with temperature. It is concluded that diurnal variation in metabolism in the small chambers resulted mainly from variation in voluntary muscular activity. On this supposition, it is estimated that the energy expended in voluntary activity averaged 2350 cal. per mouse per 24 hr. at all these temperatures, which was 12, 16, and 27% of the total daily expenditure at 10, 20, and 30 °C. respectively.