INTRODUCTION We hypothesized that microvascular disturbances in muscle tissue play a role in the reduced exercise capacity in juvenile dermatomyositis (JDM). METHODS Children with JDM, children with juvenile idiopathic arthritis (clinical controls), and healthy children performed a maximal incremental cycloergometric test from which normalized concentration changes in oxygenated hemoglobin (Δ[O2 Hb]) and total hemoglobin (Δ[tHb]) as well as the half-recovery times of both signals were determined from the vastus medialis and vastus lateralis muscles using near-infrared spectroscopy. RESULTS Children with JDM had lower Δ[tHb] values in the vastus medialis at work rates of 25%, 50%, 75%, and 100% of maximal compared with healthy children; the increase in Δ[tHb] with increasing intensity seen in healthy children was absent in children with JDM. Other outcome measures did not differ by group. CONCLUSIONS The results suggest that children with JDM may experience difficulties in increasing muscle blood volume with more strenuous exercise.
Near-infrared spectroscopy during exercise and recovery in children with juvenile dermatomyositis.