Improved exercise performance and increased aerobic capacity after endurance training of patients with stable polymyositis and dermatomyositis

Abstract

Introduction: This randomized, controlled study on patients with polymyositis or dermatomyositis was based on three hypotheses: patients display impaired endurance due to reduced aerobic capacity and muscle weakness, endurance training improves their exercise performance by increasing the aerobic capacity, and endurance training has general beneficial effects on their health status.

Methods: In the first part of this study, we compared 23 patients with polymyositis or dermatomyositis with 12 age- and gender-matched healthy controls. A subgroup of patients were randomized to perform a 12-week endurance training program (exercise group, n = 9) or to a non-exercising control group (n = 6). We measured maximal oxygen uptake (VO2 max) and the associated power output during a progressive cycling test. Endurance was assessed as the cycling time to exhaustion at 65% of VO2 max. Lactate levels in the vastus lateralis muscle were measured with microdialysis. Mitochondrial function was assessed by measuring citrate synthase (CS) and β-hydroxyacyl-CoA dehydrogenase (β-HAD) activities in muscle biopsies. Clinical improvement was assessed according to the International Myositis Assessment and Clinical Studies Group (IMACS) improvement criteria. All assessors were blinded to the type of intervention (that is, training or control).

Results: Exercise performance and aerobic capacity were lower in patients than in healthy controls, whereas lactate levels at exhaustion were similar. Patients in the exercise group increased their cycling time, aerobic capacity and CS and β-HAD activities, whereas lactate levels at exhaustion decreased. Six of nine patients in the exercise group met the IMACS improvement criteria. Patients in the control group did not show any consistent changes during the 12-week study.

Conclusions: Polymyositis and dermatomyositis patients have impaired endurance, which could be improved by 12 weeks of endurance training. The clinical improvement corresponds to increases in aerobic capacity and muscle mitochondrial enzyme activities. The results emphasize the importance of endurance exercise in addition to immunosuppressive treatment of patients with polymyositis or dermatomyositis.

Trial registration: ClinicalTrials.gov: NCT01184625.

Figure 1

Flow diagram for patients according to the CONSORT randomized, controlled trials of non-pharmacologic treatment.

Figure 2

Polymyositis and dermatomyositis patients have lower aerobic capacity and endurance exercise performance than healthy controls. A. VO₂ max vs. the corresponding power output obtained in the progressive bicycle test. B.Concentration of lactate in vastus lateralis muscle dialysate after cycling vs. cycling time in the endurance test performed at the same relative work load in all individuals. Individual data from 23 patients (open circles) and 12 healthy controls (open triangles). Mean data (± SD) from patients (filled circle) and healthy controls (filled triangle) are also shown.

Figure 3

Exercise and aerobic capacity are increased in myositis patients after 12 weeks endurance training. A. Individual data of the concentration of lactate in muscle dialysate after cycling vs. cycling time (at the same absolute work load for each subject) obtained in nine patients before (open circles) and after (filled circles) endurance training. Mean data (± SD) before (open triangle) and after (filled triangle) training are also shown. B. Same as in A but for six patients in the control group (no training). Mean data (± SD) of VO₂ max (C) and the corresponding power (D) before (white bars) and after (black bars) the 12-week intervention period in the exercise group (EG, n = 7) and the control group (CG, n = 5). E and F show mean data (± SD) of the change in VO₂ max and power after vs. before the intervention period in individual subjects.

Figure 4

Increased mitochondrial enzyme activities in muscles of myositis patients after 12 weeks of endurance training. Individual data from three patients obtained before and after 12 weeks of endurance training for cycling time at the same absolute work load for each subject (A) and the activity of two mitochondrial enzymes, CS (B) and β-HAD (C), in muscle biopsies from vastus lateralis muscle. D-F. Mean data of the difference after vs. before training (n = 3); data for five patients in the control group (no training) are also shown.