How physical activity impacts this rare disease—and why you need to know about it.

The question of whether exercise can benefit or complicate the course of myositis has been studied for the past two decades. With muscle weakness, and the fatigue and pain of myositis, many people with myositis, no matter how fit they were before diagnosis, may be wary of attempting to exercise. During the last couple of years, there has been new evidence to suggest that intensive endurance exercise can work as an anti-inflammatory treatment, increasing muscle growth and function in comparison to doing no exercise at all. Recent studies of assessing exercise’s effect on polymyositis and dermatomyositis seem to support the conclusion. 

Based on the assumption that people with myositis have less endurance due to reduced aerobic capacity and muscle weakness, researchers questioned whether endurance training could improve exercise performance by increasing the aerobic capacity. Furthermore, since endurance training is known to provide health benefits they wanted to see if the results of this type of exercise could improve health status for people with myositis. Read on to learn more about the study and its findings.

The Exercise Program

In a randomized controlled clinical trial, an intensive aerobic and endurance-based exercise program was given to a group with polymyositis and dermatomyositis and another group of healthy volunteers for comparison.  The myositis exercise group engaged in a one-hour exercise program three times a week for 12 weeks. This consisted of five-minute warm-up cycling followed by up to 30 minutes of more intense cycling where the intensity was gradually increased during the training period. Then there was 20 minutes of muscular endurance exercise of both the upper and lower limbs ending with a cool-down and stretch.

After 12 weeks: Results

The results proved to be interesting. Both groups’ exercise capacity  was measured in terms of their time to exhaustion, lactate levels, and heart rate before and after the exercise program. All of the participants in the myositis group had an increase in the cycling endurance time to exhaustion, along with lower lactate levels at the end of the exercise program. By comparison, the control group of healthy volunteers had no consistent changes in their lactate levels or endurance ability from the start to the end of the exercise program.

Two important findings came out of this study:

1. A substantially  lower endurance exercise capacity for people with polymyositis/dermatomyositis even when their disease was stable, compared to healthy people of the same age, demographics and fitness level. 

2. Although participants with myositis had limited exercise performance at the start due to weakness and inability to adequately activate the exercising muscles, the results show an improvement in endurance with cycling exercise after 12 weeks of endurance exercise training. In fact, all patients exposed to the training program improved their exercise performance, even those who had severely decreased muscle function and endurance capacity at the start. 

Researchers concluded that endurance training is effective in PM/DM patients even when they are in a chronic stable disease phase with severe muscle dysfunction. They also account for the  improvement was due to increased aerobic capacity in the myositis group after they completed their training period. 

A growing body of evidence supports the belief that exercise as a very important part of the treatment plan for adult patients with idiopathic inflammatory myopathies.

Sources: 

1. Alexanderson H. Curr Treat Options in Rheum 2018, 4:289–298.

2. Munters et al. Arthritis Research & Therapy 2013, 15:R83