AbstractObjectiveTo examine the anaerobic‐to‐aerobic power ratio in children with juvenile idiopathic arthritis (JIA) compared with healthy peers.MethodsSixty‐two patients with JIA (mean ± SD age 11.9 ± 2.1 years, range 7.2–15.9 years) with varying severity of disease and 50 healthy children (mean ± SD age 12.1 ± 2.1, range 8.4–15.9 years) participated in this study. Anaerobic power was measured using the Wingate Anaerobic Exercise Test. Aerobic power was measured using a cardiopulmonary exercise test. The power ratio was calculated as the ratio between the anaerobic mechanical power and aerobic mechanical power in watts.ResultsMean ± SD anaerobic‐to‐aerobic power ratio and peak anaerobic‐to‐aerobic ratios in children with JIA were 1.98 ± 0.51 and 3.28 ± 1.15, respectively. Compared with healthy children these differences were not statistically significant (P = 0.52 and P = 0.99, respectively). The differences in these ratios were not statistically significant when corrected for age, height, and body mass. Statistical analyses showed no significant difference between disease‐onset types of JIA for mean anaerobic‐to‐aerobic power ratio and peak anaerobic‐to‐aerobic ratio, respectively. Furthermore, there was no significant difference in the development of the power ratios between children with JIA and healthy controls, or between girls and boys.ConclusionThis cross‐sectional study suggests that the development of the anaerobic‐to‐aerobic power ratio is not statistically different in children with JIA compared with healthy peers. Exercise training of the anaerobic capacity through interval training, along with aerobic exercise training, seems warranted in the exercise therapy programs of children with JIA.