INTRODUCTION: Congenital myopathies (CM) often affect contractile proteins of the sarcomere, which could render patients susceptible to exercise-induced muscle damage. We investigated if exercise is safe and beneficial in patients with CM.

METHODS: Patients exercised on a stationary bike for 30 minutes, three times weekly, for 10 weeks at 70% of their maximal oxygen uptake (VO2max). Creatine kinase (CK) was monitored as a marker of muscle damage. VO2max, functional tests, and questionnaires evaluated efficacy.

RESULTS: Sixteen patients with CM were included in a controlled study. VO2max increased by 14% (range, 6-25%; 95% CI 7-20; p < 0.001) in the seven patients who completed training, and tended to decrease in a non-intervention group (n = 7; change -3.5%; range, -11-3%, p = 0.083). CK levels were normal and remained stable during training. Baseline Fatigue Severity Scale scores were high, 4.9 (SE 1.9), and tended to decrease (to 4.4 (SE 1.7); p = 0.08) with training. Nine patients dropped out of the training program. Fatigue was the major single reason.

CONCLUSIONS: Ten weeks of endurance training is safe and improves fitness in patients with congenital myopathies. The training did not cause sarcomeric injury, even though sarcomeric function is affected by the genetic abnormalities in most patients with CM. Severe fatigue, which characterizes patients with CM, is a limiting factor for initiating training in CM, but tends to improve in those who train.

TRIAL REGISTRATION: The Regional Committee on Health Research Ethics of the Capital Region of Denmark H-2-2013-066 and ClinicalTrials.gov H2-2013-066.