Lazzer Stefano, Busti Carlo, Agosti Fiorenza, De Col Alessandra, Pozzo Renzo, Sartorio Alessandro
Experimental Laboratory for Auxo-Endocrinological Research, Italian Institute for Auxology, IRCCS, Milan and Piancavallo (VB), Italy.
Clin Endocrinol (Oxf). 2007 Oct;67(4):582-8. doi: 10.1111/j.1365-2265.2007.02929.x. Epub 2007 Jun 21.
To measure the contribution of substrate oxidation to energy expenditure during cycling at different workloads and to identify the exercise intensity that elicits the maximum fat oxidation rate in groups of severely obese or nonobese Caucasian adolescents.
A total of 30 severely obese subjects (mean body mass index, BMI = 34.7 kg/m2; fat-mass = 39.9%) and 30 nonobese sedentary adolescents (mean BMI = 22.7 kg/m2; fat-mass = 21.8%) aged 14-16 years, participated in this study. Body composition was assessed by bioelectrical impedance. Peak oxygen uptake (VO2peak) and maximal fat oxidation rate were determined with indirect calorimetry by using a graded exercise test on an electromagnetically braked cycle ergometer.
Predicted VO2max were expressed in absolute (l/min) and relative (ml/kg FFM/min) values, and maximal work rates were not significantly different between obese and nonobese adolescents, but were significantly higher in boys than in girls. No significant differences in fat oxidation rates were found in obese and nonobese sedentary adolescents during the graded exercise test. Maximal fat oxidation was observed at an exercise intensity corresponding to (mean +/- SD) 41 +/- 3%VO2max or 58 +/- 3% HRmax. At this exercise intensity, fat oxidation rates were higher in boys than in girls (0.32 +/- 0.02 g/min vs. 0.25 +/- 0.02 g/min, P < 0.001).
Severely obese and sedentary nonobese adolescents reached maximal fat oxidation rates at 41%VO2max, which corresponds to 58% HRmax. At this exercise intensity, fat oxidation rates were higher in boys than in girls probably due to higher VO2max and absolute workload during the exercise steps for boys compared with those for girls.
测量不同工作负荷下骑行过程中底物氧化对能量消耗的贡献，并确定能使重度肥胖或非肥胖的高加索青少年群体脂肪氧化率达到最大值的运动强度。
共有30名14 - 16岁的重度肥胖受试者（平均体重指数，BMI = 34.7 kg/m²；脂肪量 = 39.9%）和30名久坐不动的非肥胖青少年（平均BMI = 22.7 kg/m²；脂肪量 = 21.8%）参与了本研究。通过生物电阻抗法评估身体成分。使用电磁制动的自行车测力计进行分级运动试验，通过间接测热法测定峰值摄氧量（VO₂peak）和最大脂肪氧化率。
预测的最大摄氧量（VO₂max）以绝对值（升/分钟）和相对值（毫升/千克去脂体重/分钟）表示，肥胖和非肥胖青少年的最大工作率无显著差异，但男孩显著高于女孩。在分级运动试验中，肥胖和久坐不动的非肥胖青少年的脂肪氧化率无显著差异。在相当于（平均±标准差）41±3%VO₂max或58±3%心率最大值（HRmax）的运动强度下观察到最大脂肪氧化。在此运动强度下，男孩的脂肪氧化率高于女孩（0.32±0.02克/分钟对0.25±0.02克/分钟，P < 0.001）。
重度肥胖和久坐不动 的非肥胖青少年在41%VO₂max时达到最大脂肪氧化率，这相当于58%HRmax。在此运动强度下，男孩的脂肪氧化率高于女孩，可能是因为与女孩相比，男孩在运动阶段的VO₂max和绝对工作负荷更高。
