Abstract
Physical activity has been recognized as an important factor for maintenance of body mass. Many studies have shown that both acute and chronic exercise produce increases on resting energy expenditure and fat oxidation. Intensity and duration of exercise are essential and have been extensively studied for preventing obesity purposes, but their relationship has not been clearly determined since the exercise required to promote this changes is unlikely to be performed by non-athletic individuals. PURPOSE: To determine the differences on resting energy expenditure and respiratory quotient after two 30-min-treadmill walking, at 60% and at 70% of maximal oxygen uptake, in young race walker athletes. METHODS: Nine male athletes 15 to 20 years of age, from a new talent race walking group, were measured by weight, height, body mass index (BMI) and percentage of body fat (%BF) by anthropometry. Maximal Oxygen uptake (VO2max) was obtained by an exercise stress testing before to perform two 30-min-treadmill exercises, at 60% and at 70% of VO2max, which were randomly accomplished 3 to 5 days apart. Resting energy expenditure (REE) and respiratory quotient (RQ) were measured by indirect calorimetry before and after each submaximal workload. Descriptive statistics and paired t test at a p<0.05 significance level were used. RESULTS: Athletes were 17.8 ± 2.3 years old, had 21.6 ± 1.6 Kg/m2 of BMI, 9.2 ± 2.0 %BF and 60.6 ± 6.4 mL.kg−1.min−1 of VO2max. REE was higher after both workload intensities than before (1490 ± 205 vs 1837 ± 187 Kcal/day and 1437 ± 163 vs 1888 ± 265 Kcal/day, pre and post 60% and 70% of VO2max exercises respectively, p<0.01). No differences were seen between the two 30-min-treadmill walking where the increases represented the 24.4% and 31.3%, respectively. RQ was 13% lower after both exercises than before (0.91 ± 0.08 vs 0.79 ± 0.07 and 0.90 ± 0.10 vs 0.78 ± 0.06 pre and post 60% and 70% intensities respectively, p<0.01). CONCLUSIONS: A short session of aerobic exercise at 60% or 70% of VO2max increases REE in young athletes regardless their different intensities. They showed similar higher fat oxidation after both submaximal workouts. Acknowledgements: This research was supported by CONACyT Government of Mexico, grant 9702009.
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