Background: Polymyositis (PM) and Dermatomyositis (DM) are chronic, inflammatory and autoimmune skeletal muscle disorders characterized by reduced muscle strength, fatigue and myalgia. While inflammation causes muscle damage in the early phase, metabolic alterations such as an impairment of oxidative metabolism seem to be responsible for the disability in the chronic phase of the disease.
Aim: To assess muscle oxidative efficiency and to test the effect of aerobic training in a group of PM/DM patients.
Design: A case-control study and a within-group comparison. SETTING. Outpatients of the Unit of Neurorehabilitation of the University Hospital of Pisa.
Population: 20 patients with myositis (15 PM and 5 DM) and 15 healthy subjects as a control group.
Methods: The test consisted of an incremental, sub-maximal aerobic exercise on a treadmill; haematic lactate was assessed at rest and after 1', 5', 10' and 30' minutes from the end of the exercise. A within-group comparison was conducted on four of the PM patients (P group). They were subjected to six weeks aerobic training. Lactate curve and functional tests were assessed before and after the treatment.
Results: A precocious fatigability and significantly higher values of lactate at rest and after the exercise were observed in patients. In the P group mean lactate levels were significantly decreased after the treatment and an improvement of muscle performance was observed.
Conclusion: Abnormal blood lactate levels suggested an impaired muscle oxidative efficiency in PM/DM patients. A specific aerobic training program reduced lactate levels and relieved fatigue symptoms in a within-group of four of the PM patients.
Clinical rehabilitation impact: Such a specific aerobic training program could be introduced in everyday practice for the rehabilitative treatment of PM/DM patients.