Objective. To assess aerobic fitness and exercise capacity in patients with juvenile idiopathic arthritis (JIA) and to determine subgroup differences.
Methods. Thirty-four patients diagnosed with JIA and 21 healthy sedentary volunteers were studied. Aerobic fitness was determined by measuring peak power and peak oxygen uptake (VO2peak) during an incremental cycling test. The patient group consisted of systemic JIA (n = 8), polyarticular JIA (n = 13), oligoarticular JIA (n = 7), and enthesitis-related arthritis (ERA, n = 6). Results from different subgroups of JIA were compared to determine subgroup differences.
Results. All subjects tolerated maximal exercise testing well. The JIA group had lower aerobic fitness than controls. In our comparison of JIA subgroups, we found no significant differences in cardiopulmonary measures. The ERA group had higher aerobic capacity than other subgroups. There was no difference in exercise capacity between patients with active disease (n = 10) and those in remission (n = 24).
Conclusion. We suggest that heterogeneity in VO2peak levels among JIA patients is due to subgroup differences. Exercise programs for improvement of aerobic fitness should be individualized or at least be modified according to different subgroups.