A 45-minute Vigorous Exercise Bout Increases Metabolic Rate for 14 Hours

Amy M. Knab; R. Andrew Shanely; Karen D. Corbin; Fuxia Jin; Wei Sha; David C. Nieman

Disclosures

Med Sci Sports Exerc. 2011;43(9):1643-1648. 

In This Article

Discussion

This study found that in healthy young male subjects, vigorous exercise (57% W max or 73% V̇O2max) for 45 min starting at 11:00 a.m. resulted in 519 kcal expended above the rest day. Postexercise energy expenditure was significantly elevated for 14.2 h compared with the rest day, corresponding to an additional 190 ± 71.4 kcal that included 3.5 h and 32.0 ± 39.3 kcal during the early sleep period. Energy intake and expenditure were tightly matched on both the rest and exercise days to ensure zero energy balance under both conditions, and the daily activities of living were controlled.

Most previous studies evaluating the effect of single exercise bouts on postexercise energy expenditure have used Douglas bag and metabolic cart systems, with widely varying results.[6,10,11,13,16,17,22,30] This variation is related to multiple factors including noncontinuous measurement of energy expenditure, the use of preexercise RMR as the criteria for normal levels,[6,11,22] and the lack of tight control of daily activities of living. Despite these limitations, previous studies emphasize the importance of exercise intensity to produce sizeable increases in postexercise energy expenditure.[6] For example, Phelain et al.[23] found that when subjects burned the same amount of calories either through high- or low-intensity exercise, energy expenditure remained elevated at 3 h after exercise only for the high-intensity condition. The magnitude of postexercise energy expenditure is greatest when the body experiences significant physiologic stress during prolonged and high-intensity exercise.[4]

Postexercise energy expenditure was significantly elevated for 14.2 h when compared with the rest day, adding 37% or 190 ± 71.4 kcal to the net energy expenditure of the 45-min cycling bout. The duration of increase in postexercise energy expenditure is comparable to Bahr et al.,[3] who assessed the effect of high-intensity exercise on excess postexercise oxygen consumption under tightly controlled conditions. In this study, subjects rested or exercised early in the morning and then remained supine in bed for 24 h while being fed three meals. Using Douglas bag methods, oxygen consumption remained elevated after 12 h after 40 min of exercise at 69% V̇O2max. Our magnitude of increase in postexercise energy expenditure (37%), however, is substantially above the 14% reported by Bahr et al..[3]

Investigators have used metabolic chambers to measure the influence of exercise on fuel substrates and total 24-h energy expenditure,[18,19,26] but only one other chamber study has measured the effect of a single exercise bout on resting energy expenditure.[9] Dionne et al.[9] reported no effect of a midafternoon 60-min moderate-intensity exercise bout (50% V̇O2max) on 24-h energy expenditure in young adult males compared with a rest day under energy balance conditions. The authors attributed the absence of postexercise changes in energy expenditure to the ingestion of a snack immediately after the 60-min exercise bout.[9] This snack contained the same amount of energy and macronutrients oxidized during the exercise bout, and the authors speculated that the snack ingestion caused an accelerated replenishment of glycogen stores and recovery of energy balance. Our results argue against this rationale. The higher exercise intensity in our study caused a greater homeostatic disturbance and more than likely explains the contrast in the magnitude and duration of postexercise energy expenditure.

The prolonged increase in RMR after exercise observed in the current study could have been caused by several contributing factors including an enhanced energy flux. Subjects in our study were maintained in energy balance during both the exercise and rest days, resulting in an added energy intake of 659 kcal on the exercise day. The increased energy intake balanced against energy expenditure (energy flux) has been shown in several studies to contribute to the elevated 24-h energy expenditure on exercise days or in trained individuals.[5,8,12] Other potential factors include homeostatic disturbance from vigorous exercise, as theorized by Bahr et al.,[4] increased circulation of stress hormones and sympathetic tone,[14] and recovery from decreased muscle glycogen levels.[14]

Our data support that vigorous cycling (~70% V̇O2max) has a significant effect on 24-h energy expenditure under conditions when energy intake is balanced with energy expenditure. The magnitude (190 kcal) and duration (14.2 h) of net energy expenditure after 47-min cycling at 73% V̇O2max are greater than previously reported in most studies conducted outside a metabolic chamber. The 24-h net energy expenditure difference between exercise and rest days was 750 kcal, a meaningful quantity over time if two or three such exercise bouts are inserted into the weekly schedule and energy intake is controlled.[3,4,6]

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