RESUMO
Trials regarding physical exercise in dermatomyositis (DM) and polymyositis (PM) are heterogeneous. We aimed to summarize and critically analyze the available evidence to support the hypothesis that exercise is safe and improves strength and aerobic capacity. We performed a systematic review of clinical trials regarding physical exercise in dermatomyositis and polymyositis, without time restriction. We included studies from MEDLINE, EMBASE, SciELO, and Web of Science, published in English, Portuguese, or Spanish, and reporting outcomes related to safety, muscle performance, or aerobic capacity. The certainty of evidence was evaluated in accordance with the GRADE methodology. Meta-analysis was carried using pooled standardized mean differences (SMD) with 95% confidence interval as effect measure. We included 19 studies and 298 patients. The certainty of evidence was downgraded due to unbalanced confounding variables. The meta-analysis demonstrated improvements in strength (SMD [95% CI] = 0.61 [0.37-0.85], P < .00001) and aerobic capacity (SMD [95% CI] = 0.82 [0.29-1.34], P = .002), with no difference in creatine phosphokinase levels (SMD [95% CI] = - 0.23 [- 0.5-0.03], P = .08) after the interventions. No exacerbation was reported, and results were favorable in all stages of disease and ages, but might be different in the future with new classification criteria for PM and the inclusion of other idiopathic inflammatory myopathies. Novel approaches such as blood flow restriction training and aquatic plyometric exercises were promising. Physical exercise in DM/PM patients of all ages is probably safe and moderately improves muscle strength and aerobic capacity.