OBJECTIVE: To determine whether aerobic capacity is normal in boys with different types of hemophilia compared with healthy peers and whether the level of aerobic capacity correlates with the amount of physical activity, joint health status, muscle strength, and anthropometrics.

STUDY DESIGN: 47 patients (mean [SD] age, 12.9 [3.2] years; age range, 8.2-17.4 years) from the "Van Creveldkliniek" of the University Medical Center Utrecht, participated. Anthropometry, muscle strength, joint impairment, functional ability, and aerobic capacity were measured. The amount of energy expenditure during daily living was assessed.

RESULTS: All boys were able to perform at maximal or near-maximal level on exercise tests, and none of them reported bleeds or other adverse events. Relative peak oxygen, peak heart rate, and peak working capacity were significantly lower compared with healthy control subjects. 30% had Z-scores >2 for weight. Total muscle strength was normal, and almost no joint impairment and no decrease in functional ability were found.

CONCLUSION: The aerobic capacity of children with hemophilia is still lower than the normal population, whereas their overall muscle strength is comparable with healthy peers. The functional ability does not differ from healthy peers, and joint health status showed very minor impairments. A substantial proportion of Dutch children with hemophilia was overweight, without showing a reduction in the amount of self-reported physical activities.