Substrate oxidation in overweight boys at rest, during exercise and acute post-exercise recovery.

School of Sport Science, Exercise and Health, The University of Western Australia, WA, Australia.
International journal of pediatric obesity: IJPO: an official journal of the International Association for the Study of Obesity (Impact Factor: 2). 01/2011; 6(2-2):e615-21. DOI: 10.3109/17477166.2010.543684
Source: PubMed

ABSTRACT To compare substrate oxidation between normal weight (n = 10) and overweight (n = 10) boys at rest, during exercise at 50% VO(2peak) and during the first 30 minutes of recovery post-exercise.
Twenty boys (8-11 years) were tested over two separate occasions. At the first session, body composition was measured by Dual-Energy X-ray Absorptiometry and peak aerobic capacity (VO(2peak)) was assessed using an incremental treadmill protocol. At least one week later, substrate oxidation was determined via indirect calorimetry in the fasted state at rest, during 10 minutes of exercise at 50% VO(2peak) and during the first 30 minutes of acute recovery post-exercise.
There were no significant differences in substrate oxidation between the two groups at rest or during exercise. However, during early recovery, respiratory exchange ratio (RER) transiently increased in the overweight boys (p = 0.034) but not in the normal weight boys (p = 0.796), with a shift towards greater carbohydrate oxidation in the former group at 15-20 (p = 0.044) and 25-30 (p = 0.052) minutes post-exercise. In contrast, absolute post-exercise fat oxidation was similar between the two groups.
Overweight boys may oxidise fat less efficiently than normal weight boys during recovery post-exercise, deriving a greater proportion of energy from carbohydrate oxidation.

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    ABSTRACT: The objective was to examine the effect of adding sprints to continuous exercise at the intensity that maximises fat oxidation (Fat(max)) on energy expenditure, substrate oxidation, enjoyment and post-exercise energy intake in boys. Nine overweight and nine normal weight boys (8-12 years) attended the laboratory on three mornings. First, body anthropometrics, peak aerobic capacity and Fat(max) were assessed. On the remaining two sessions, resting metabolic rate was determined before participants completed 30 min of either continuous cycling at Fat(max) (MOD) or sprint interval exercise consisting of continuous cycling at Fat(max) interspersed with four-second maximal sprints every two minutes (SI). Energy expenditure and substrate oxidation were measured during exercise and for 30 min post-exercise, while participants completed a modified Physical Activity Enjoyment Scale (PACES). This was followed by a buffet-like breakfast to measure post-exercise energy intake. Fat oxidation rate was similar between groups and protocols (P>0.05). Both groups expended more energy with SI compared to MOD, resulting from increased carbohydrate oxidation (P<0.05), which was not compensated by increased energy intake. Participants indicated that they preferred SI more than MOD, although there was no significant difference in PACES score between the protocols (P>0.05). In summary, the addition of short sprints to continuous exercise at Fat(max) increased energy expenditure without compromising fat oxidation or stimulating increased post-exercise energy intake. The boys preferred SI and did not perceive it to be any harder than MOD, indicating that sprint interval exercise should be considered in exercise prescription for this population.
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Jun 1, 2014