Duchenne Muscular Dystrophy: Gowers Sign, Submaximal Exercise and Contractures
In short
Duchenne Muscular Dystrophy requires careful exercise dosing. Understand why high-resistance eccentric loading causes sarcolemmal damage, and learn safe submaximal protocols.
In this guide (4 sections)
Understanding Duchenne Muscular Dystrophy (DMD)
Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular disorder caused by mutations in the dystrophin gene. Absence of dystrophin leaves the muscle sarcolemma fragile and vulnerable to mechanical contraction-induced tearing, leading to progressive muscle fiber necrosis and fibrofatty replacement.
Between ages 3 and 5, boys present with frequent falling, difficulty running, calf pseudohypertrophy, and the classic Gowers sign (using their hands to walk up their thighs to rise from the floor due to severe gluteal and quadriceps weakness).
The Cardinal Rule: Strict Avoidance of High-Resistance Eccentric Exercise
The fundamental principle in DMD physiotherapy is avoiding contraction-induced muscle damage. High-intensity resistance training and eccentric muscle contractions (such as running downhill, jumping, or heavy weights) generate mechanical stress that ruptures dystrophin-deficient muscle membranes, accelerating disease progression.
Instead, exercise is prescribed strictly as low-resistance, submaximal aerobic exercise (such as swimming, hydrotherapy, and assisted stationary cycling).
| Exercise Modality | Safety Status | Physiological Rationale | Clinical Recommendation | |
|---|---|---|---|---|
| Hydrotherapy and Swimming | Highly Recommended | Buoyancy unloads gravity; enables active movement without mechanical joint shock. | 30 to 45 minutes, 2 to 3 times weekly in heated pool (32-34°C). | |
| Low-Resistance Cycling | Recommended | Concentric reciprocal pedaling preserves cardiovascular fitness and joint range. | 15 to 20 minutes at submaximal pace (Borg RPE 11-13). | |
| Passive Night Splinting | Essential Mainstay | Sustained low-load stretching prevents equinus contractures of Achilles tendon. | Custom solid AFOs worn nightly for 6 to 8 hours. | |
| Eccentric Loading and Plyometrics | Strictly Prohibited | High-force elongation causes irreversible sarcolemmal rupture and rapid fibrosis. | Contraindicated across all stages of muscular dystrophy. |
Contracture Management Across Disease Stages
Contractures develop early in the gastrocnemius-soleus, hamstrings, and iliotibial band. Daily stretching performed by trained parents and physiotherapists is vital to prolong independent ambulation.
- Daily Home Stretching: Perform passive, slow, sustained stretching of the heel cords, hamstrings, and hip flexors for at least 60 seconds per muscle group twice daily.
- Standing Frames in Non-Ambulatory Stage: Once independent walking ceases (typically between 9 and 12 years), daily standing in a passive standing frame for 60 minutes preserves bone mineral density and retards scoliosis.
- Respiratory Therapy: Introduce lung volume recruitment (air stacking via resuscitation bag) and assisted coughing protocols as forced vital capacity (FVC) declines.
Frequently Asked Questions
Can corticosteroids replace physiotherapy in DMD?
No. Corticosteroids (prednisone or deflazacort) slow muscle strength decline and prolong ambulation by 2 to 3 years, but daily stretching and submaximal exercise remain essential to prevent contractures and postural deformities.
Why do calves appear enlarged if the muscles are weak?
This is pseudohypertrophy. The enlarged appearance is not due to true muscle growth, but rather extensive infiltration of dead muscle tissue by adipose and fibrous connective tissue.
What is the Vignos functional mobility scale?
The Vignos scale grades lower extremity functional decline from Grade 1 (walks and climbs stairs without assistance) down to Grade 10 (confined to bed).
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