The effect of exercise on post-exercise metabolic rate

The purpose of this study was to determine whether the energy expenditure at rest following exercise was equal to the energy expenditure at rest when no exercise was performed.

Five female students volunteered as subjects. The subjects exercised on the treadmill for thirty minutes at seventy percent of their maximal oxygen uptake on Monday and Wednesday. No exercise was performed on Tuesday and Thursday. Measurements of oxygen uptake were made on each day and at the same time, corresponding to 1-2-3 and 4 hour intervals post-exercise. Each subject stayed in the supine position for five minutes prior to each measurement period. The subject then inhaled room air through a two-way respiratory valve and exhaled into a meterological balloon. A sample of the expired gas was collected for a fifteen minute period in each of the 1-hour intervals. The expired gas was analyzed for 0₂ and CO₂ and the expiratory ventilation volumes were determined. Oxygen uptake was calculated and data were analyzed with a repeated measures ANOVA. The statistical analysis system (SAS) program at the University of Tennessee Computer Center was used for most statistical calculations. A t-test was also used to determine the differences between the two exercise days and the two rest days values and the individual time periods.

The analysis of variance yielded a significant F ratio for the treatment, showing that there was a higher resting energy expenditure on the days exercise was taken compared to days when no exercise was performed. The analysis of variance also showed a significance in the subject*time interaction, pointing out that the subjects differed in their oxygen uptakes during the four measurement periods (p<.05). The resting energy expenditure decreased significantly from the first day to the second day when the treatment was repeated (p<.05).

The resting energy expenditure was 18.4 kcal higher for the four-hour period after activity, compared to the corresponding time period when no exercise was performed. For an average person exercising at a work rate of 9 METS, this would equal the energy expenditure during two minutes of the exercise. This additional energy expenditure would result in a weight loss of approximately one pound of fat per year. Though this value is very small, it is an extra loss. A person is already losing a certain amount of calories due to the exercise itself, thus the post-exercise energy expenditure becomes a reward for the work already done.

This finding further supports the importance of exercise in weight and fitness courses as an integral part of an effective program to stay in a negative caloric balance.