Residual effect of graded levels of exercise on metabolic rate

The hypothesis that exercise induces a residual effect on metabolic rate only when the intensity exceeds a certain threshold was tested by studying 10 healthy, untrained adults performing graded levels of bicycle ergometry on five separate occasions. The exercise consisted of four 30-min periods at intensities ranging from 0 to 100 Watts. Energy expenditure was measured by continuous indirect whole-body calorimetry. The highest level of exercise increased 24-h energy expenditure by 34 per cent. Food intake was modified for each measurement in order to maintain energy balance. Sleeping and basal metabolic rates on the night following exercise were raised even at low intensities of exercise. There was an almost linear dose-response relationship and no evidence of a threshold. However, the effect was small, amounting to only 5.8 per cent overnight and 3.9 per cent in the morning following 2 h exercise at over 60 per cent VO2 max during the preceding day. This suggests that the residual energy expenditure incurred after moderate levels of exercise is unlikely to be a very useful adjunct to slimming regimes.