Abstract
BackgroundExercise is often used to obtain a negative energy balance. However, its effects on body weight reduction are usually below expectations. One possible explanation is a reduction in spontaneous physical activity (SPA) after exercise since the increase in energy expenditure caused by the exercise session would be offset by the decrease in SPA and its associated energy cost. Thus, we evaluated the effects of a single bout of moderate exercise at individualized intensity on spontaneous physical activity. The impact of the single bout of exercise was determined in early adulthood and at the transition to middle age.MethodsMale C57bl/6j (n = 10) mice were evaluated at 4 (4 M) and 9 (9 M) months of age. One week after a treadmill Maximal Exercise Capacity Test (MECT), mice performed a 30-min single bout of exercise at 50 % of the maximal speed reached at MECT. An infrared-based system was used to determine locomotor parameters (SPA and average speed of displacement, ASD) before (basal) and immediately after the single bout of exercise for 48 h (D1, 0-24 h; D2, 24-48 h). Food intake was measured simultaneously. Data were analyzed by GEE and statistical significance was set at p < 0.05.ResultsBasal SPA declined from 4 M to 9 M (p = 0.01), but maximal exercise capacity was similar. At both ages, SPA and ASD decreased significantly (p < 0.0001) on day 1 after exercise. On D2, SPA returned to basal levels but ASD remained lower than basal (p < 0.001). The magnitude (% of basal) of change in SPA and ASD on D1 and D2 was similar at 4 M and 9 M. Food intake did not change at 4 M but decreased on D2 at 9 M.ConclusionsA single bout of moderate exercise decreases physical activity in the first 24 h and average speed of locomotion in the 48 h following exercise. This compensation is similar from early adulthood to the transition to middle age. The decrease in both the amount and intensity (speed) of SPA may compensate for the increase in energy expenditure induced by exercise, helping to understand the below-than-expected effect of exercise interventions to cause a negative energy balance.
Highlights
Exercise is often used to obtain a negative energy balance
The magnitude of the fall in spontaneous physical activity (SPA) is similar from early adulthood to the transition to middle age;
There was a significant effect of age on SPA (p = 0.01), which reduced significantly at 9M compared to 4M (Fig. 1A)
Summary
Exercise is often used to obtain a negative energy balance. its effects on body weight reduction are usually below expectations. We evaluated the effects of a single bout of moderate exercise at individualized intensity on spontaneous physical activity. Among the mechanisms which may be involved in the exercise below-than-expected energy deficit are increased energy intake [1] and decreased energy expenditure, including decreased basal metabolic rate and spontaneous physical activity [2, 3]. Spontaneous physical activity (SPA) consists of daily life activities excluding structured, purposeful exercise. It generally comprises low-intensity physical activities (LIPA), with low energetic costs [4]. The contributions of SPA to energy balance, are less clear, despite studies demonstrating protective effects against weight gain in response to overfeeding [7] and an inverse correlation with the rate of body weight change [8]
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