Maximal aerobic power during running and cycling in obese and non-obese children

The maximal aerobic capacity while running and cycling was measured in 22 prepubertal children (mean age ± SD 9.5 ± 0.8 years): 14 obese (47.3 ± 10 kg) and 8 non-obese (31.1 ± 6.1 kg). Oxygen consumption (V̇O₂) and carbon dioxide production were measured by an open circuit method. Steady state V̇O₂ was determined at different levels of exercise up to the maximal power on the cycloergometer (92 W in obese and 77 W in non-obese subjects) and up to the maximal running speed on the treadmill at a 2% slope (8.3 km/h in obese and 9.0 km/h in lean children). Expressed in absolute values, the V̇O(2max) in obese children was significantly higher than in controls (1.55 ± 0.29 l/min versus 1.23 ± 0.22 l/min, p <0.05) for the treadmill test and comparable in the two groups (1.4 ± 0.2 l/min versus 1.16 ± 0.2 l/min, ns) for the cycloergometer test. When V̇O(2max) was expressed per kg fat free mass, the difference between the two groups disappeared for both tests. These data suggest that obese children had no limitation of maximal aerobic power. Therefore, the magnitude of the workload prescribed when a physical activity program is intended for the therapy of childhood obesity, it should be designed to increase caloric output rather than to improve cardiorespiratory fitness.