Managing Quadriceps Disuse Atrophy in Duchenne Muscular Dystrophy
You should engage in low-intensity, self-regulated voluntary exercise to prevent disuse atrophy in your quadriceps, as this approach has been shown to improve muscle function and mass without exacerbating dystrophic damage. 1
Evidence for Exercise in DMD
The concern about exercise causing harm in DMD is valid but outdated when applied to appropriate exercise protocols:
- Voluntary, self-regulated exercise is safe and beneficial in severe DMD models, actually improving muscle mass, force generation, and reducing fibrosis rather than worsening the dystrophy 1
- High-volume voluntary wheel running (averaging 1.84 km/day) in severe D2.mdx mice—a clinically relevant DMD model—increased selective muscle mass and ex vivo force generation compared to sedentary counterparts 1
- The exercise did not exacerbate dystrophic pathology but instead attenuated the fibrotic profile 1
Specific Exercise Recommendations
Low-intensity physical training is the appropriate approach:
- Active and/or assisted cycling training for legs and arms over 6 months has been studied specifically for DMD patients to preserve muscle endurance and functional abilities 2
- The key is that exercise should be self-regulated and voluntary, allowing you to control intensity based on how you feel 1, 2
- Volitional exercise promotes a shift toward slower, more oxidative muscle fibers and improves mitochondrial function, which are protective adaptations 1
Critical Distinction: Disuse vs. Overuse
Your instinct to prevent disuse atrophy is correct, but the approach matters:
- Disuse atrophy is a real secondary problem in DMD—the increasing effort to perform activities, fear of falling, and use of aids indirectly impair function beyond the primary disease process 2
- However, high-intensity or eccentric exercise could potentially cause harm due to defective nitric oxide release mechanisms in DMD muscle during exercise 3
- The solution is low-intensity, frequent, self-paced activity rather than aggressive strengthening 1, 2
What to Avoid
Respiratory muscle training cannot be fully endorsed because some studies show it may lead to increased muscle damage due to defective protective mechanisms in DMD muscle 3
Complementary Management
While addressing disuse atrophy through appropriate exercise:
- Glucocorticoid therapy (prednisone 0.75 mg/kg/day or deflazacort 0.9 mg/kg/day) is essential as the only medication that slows decline in muscle strength and function 3, 4, 5
- Physical therapy should include heel cord stretching to prevent contractures 6
- Monitoring by physical therapists every 4 months is recommended to adjust your exercise program 3
The bottom line: Your quadriceps will benefit from regular, self-paced, low-intensity activity like assisted cycling rather than remaining sedentary, as long as you avoid high-intensity or exhaustive exercise. 1, 2