Abstract
IntroductionThis 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.MethodsIn 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).ResultsExercise 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.ConclusionsPolymyositis 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 registrationClinicalTrials.gov: NCT01184625
Highlights
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
The mechanisms that lead to muscle weakness are not fully clarified but both immune-mediated and non-immune-mediated mechanisms are thought to be involved in the disease process and the latter mechanisms include endoplasmic reticulum (ER) stress, hypoxia, autophagy and mitochondrial pathology [3,4,5]
The RQ at VO2 max, the maximum heart rate, and Borg ratings of peripheral and central exertion were similar in patients and healthy controls (HC) (Table 2)
Summary
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. Patients with established PM/DM display fewer oxidative slow-twitch type I muscle fibers and lower aerobic capacity compared to healthy controls [9,10,11]. Thickened endothelial cells, reduced capillary blood supply and low total number of capillaries may impair oxygen transport to the muscle fibers in inflammatory myopathies [12,13]. Up-regulation of hypoxia-related proteins, such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 (HIF-1), has been observed in muscle of patients with inflammatory myopathies [13,14]
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