RESUMO
Running and cycling are two modalities of exercise commonly used to promote fat oxidation in weight loss programs for obese people. In order to design appropriate training programs, the objective of the present study was to compare fat oxidation and energy expenditure at different intensities of exercise during running and cycling in obese adolescent boys. Eleven healthy obese adolescent boys [mean age 13 +/- 1.2 years, mean weight 73.1 +/- 7.6 kg, and body mass index 27.5 +/- 2.5 kg/m2] voluntarily participated in this study. Subjects performed 2 incremental graded exercise tests on a cycle ergometer and a motorized treadmill. Heart rate, mean oxygen consumption and carbon dioxide generation during the last two minutes of each level of test were measured and respiratory exchange ratio was calculated. Energy expenditure and fat and carbohydrate oxidation rates were calculated at different intensity levels. At comparable and similar heart rates, the fat oxidation rate was significantly higher during running, compared to cycling over a wide range of intensities [p<0.05], except at intensities of 20w and 170w, as was the total energy expenditure, compared to cycling [266 +/- 43 vs237 +/- 39 kJ/min] [p<0.05]. Carbohydrate oxidation was, however, significantly higher during cycling compared to running, at intensities of 45w, 70w and 95w. It is concluded that for obese adolescents, in order to lose weight and reduce body fat mass [increased energy expenditure and promoted fat oxidation in a certain level of cardio-vascular responses], moderate intensity of running would be more effective than cycling