Objective: To investigate the short-term effects of exercise on muscle inflammation in children with juvenile dermatomyositis (juvenile DM). Magnetic resonance imaging (MRI), muscle strength, and blood parameters were used as outcome measures.
Methods: Children with active juvenile DM, inactive juvenile DM, and healthy children were assessed for muscle strength (using myometry) and function, and MRI T2-weighted relaxation time measurement; blood was obtained from patients with juvenile DM. A standardized physiotherapy-led exercise program was completed, and the MRI was performed immediately afterwards. All children were reassessed with myometry and MRI at 30 minutes and 60 minutes, and repeat blood tests were performed at 60 minutes for the patients with juvenile DM.
Results: Ten children with active juvenile DM, 10 with inactive juvenile DM, and 20 healthy controls completed the study. Muscle inflammation assessed by MRI, myometry, and blood parameters did not change significantly in response to exercise either immediately after or up to 60 minutes after the exercise program in any group.
Conclusion: In the short term, a single bout of exercise does not change the degree of inflammation within the muscles of children with active or inactive juvenile DM or in healthy children. The data suggest that, at least in this time period, there is no evidence that exercise increases the inflammation within the muscles. We propose therefore that a moderate exercise program is safe for children with juvenile DM.