Aerobic Fitness Indices of Children Differed Not by Body Weight Status but by Level of Engagement in Physical Activity

Background: Moderate-to-vigorous physical activity (MVPA) improves aerobic fitness in children, which is usually assessed by maximal oxygen consumption. However, other indices of aerobic fitness have been understudied. Objective: To compare net oxygen (VO2net), net energy consumption (E-net), net mechanical efficiency (MEnet), and lipid oxidation rate in active and inactive children across body weight statuses. Design: The sample included normal-weight, overweight, and obese children of whom 44 are active (>= 30 min of MVPA/d) and 41 are inactive (<30 min of MVPA/d). VO2net, E-net, MEnet and lipid oxidation rate were determined during an incremental maximal cycling test. Results: Active obese participants had significantly lower values of VO2net and E-net and higher MEnet than inactive obese participants at all load stages. In addition, active obese participants showed a significantly higher lipid oxidation rate compared with inactive obese and active overweight and normal-weight participants. VO2net, E-net, and MEnet were similar across active children, regardless of body weight status. Conclusions: Thirty minutes or more of MVPA per day is associated with a potentiation of aerobic fitness indicators in obese prepubertal children. Moreover, the indices of aerobic fitness of inactive obese children are significantly different from those of active obese and nonobese ones.