Two-Year Longitudinal Changes in Lower Limb Strength and Its Relation to Loss in Function in a Large Cohort of Patients With Duchenne Muscular Dystrophy.
Abhinandan Batra, Ann Harrington, Donovan J Lott and 20 others
PMID 29734234WHAT IT FOUND
Over two years, strength normalized to body size declined in boys with Duchenne muscular dystrophy, widening the gap with healthy peers.
However, changes in leg strength only modestly predicted loss of walking ability. Plantar flexor strength was a better predictor of losing function than knee extensor strength.
Key findings
01When strength was normalized to body surface area, both knee extensors and plantar flexors showed a significant decline over two years in patients with Duchenne muscular dystrophy.
02Plantar flexor strength normalized to body surface area was the best predictor of losing the ability to perform functional tasks, except for rising from supine.
03The correlation between two-year changes in strength and changes in functional performance was weak, with no correlation coefficient exceeding 0.33.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study included only boys who could already walk 100 meters and climb stairs, so results may not apply to non-ambulatory patients. All participants were taking corticosteroids, which may alter the natural progression of muscle weakness compared to untreated patients. The correlation between strength loss and functional loss was weak, indicating that factors other than leg strength, such as trunk strength or contractures, drive functional decline. Subjects who lost the ability to perform tests were assigned extreme values, which may bias longitudinal analysis.
Declared interests
None declared.
The easy way to misread this
Do not interpret the lack of significant decline in absolute plantar flexor strength as evidence that this muscle group is spared. When normalized for body size, plantar flexor strength did decline significantly, and it was the best predictor of functional loss.