Aerobic Training in Patients with Congenital Myopathy

Abstract

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.

Trial registration: ClinicalTrials.gov NCT02020187.

Fig 1. Flowchart, maximal oxygen uptake, workload and plasma creatine kinase levels.

(A) 16 patients with CM were included in the study. Four patients from the 1^st training group completed the training program. A non-intervention group of seven CM patients were tested twice, 10 weeks apart, before they participated in the training program (2^nd training group). Only 3 patients from the non-intervention group completed the subsequent training program. In total, nine patients dropped out of the training program. (B) VO_2max before and after 10 weeks of aerobic training in seven CM patients with an improvement corresponding to 215 ml O₂ · min^-1 (CI 121–308 ml O₂ · min^-1, * p = 0.001) (left bars). VO_2max before and after 10 weeks of normal daily living in seven patients with CM (right bars). Black bars represent values before, and gray bars represent values after. The change seen in the intervention group was significant compared to the change in the non-intervention group (mixed Anova, p < 0.001). (C) Maximal workload before and after 10 weeks of aerobic training in seven CM patients who improved W_max by 18 W (CI 11–24 W, ** p = < 0.001) (left bars). W_max before and after 10 weeks of normal daily living in seven CM patients (right bars). Black bars represent values before, and gray bars represent values after. The change seen in the intervention group was significant compared to the change in the non-intervention group (mixed Anova, p < 0.001). (D) Dots represent plasma CK levels at week 0, 3 and 10 from the seven CM patients who finished the training program. All values are within the normal range or slightly elevated when corrected for age and gender. VO_2max: maximal oxygen uptake; CM: congenital myopathy; W_max: maximal workload; CK: creatine kinase.

Fig 2. Baseline muscle strength evaluated by MRC score in the seven patients who finished the training program (black bars) and in the nine patients who dropped out of the training program (gray bars).

A significant difference was found between the two groups in three muscle groups; ankle plantar flexion, * p < 0.001; ankle dorsal flexion, ** p = 0.032; hip abduction, *** p = 0.014. Error bars indicate standard error of the mean.