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
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Updated: Feb 11, 2026
Measurements of Motor Function and Other Clinical Outcome Parameters in Ambulant Children with Duchenne Muscular Dystrophy
Published on: January 12, 2019
Abhinandan Batra1, Ann Harrington, Donovan J Lott
1From the Department of Physical Therapy, University of Florida, Gainesville, Florida (AB, DJL, RW, CRS, WM, SCF, WT, JKD, KV); Department of Physical Therapy, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania (AH); Department of Statistics, University of Florida, Gainesville, Florida (DX, MJD); Department of Physical Therapy, University of Toronto, Toronto, Ontario, Canada (SM); Advanced Imaging Research Center, Oregon Health and Science University, Portland, Oregon (WDR); Department of Neurology, Oregon Health and Science University, Portland, Oregon (IA); Department of Occupational Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania (RB); Department of Pediatrics, Nemours Children's Hospital, Orlando, Florida (RF); Department of Pediatrics, Oregon Health and Science University, Portland, Oregon (EF); Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania (GT); Department of Pediatrics, University of Florida, Gainesville, Florida (BB); Division of Neurology, Oregon Health and Science University, Portland, Oregon (BR); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (HLS); and Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida (GW).
Insights
Lower limb muscle strength significantly declines in children with Duchenne muscular dystrophy over two years. This strength loss partially predicts functional decline, but other factors also contribute to reduced mobility.
Area of Science:
- Neuromuscular Disorders
- Pediatric Rehabilitation
- Biomedical Engineering
Background:
- Duchenne muscular dystrophy (DMD) is a progressive genetic disorder characterized by muscle degeneration.
- Lower limb muscle strength is crucial for ambulation and functional independence in children with DMD.
- Longitudinal data on strength decline and its relationship with functional performance in DMD is essential for effective management.
Purpose of the Study:
- To investigate the longitudinal changes in lower limb muscle strength over two years in children with DMD.
- To assess the impact of disease progression on plantar flexor and knee extensor strength.
- To examine the correlation between muscle strength and functional performance in this cohort.
Main Methods:
- A cohort of 77 children with DMD was followed for two years.
- Plantar flexor and knee extensor strength, along with performance on timed functional tests, were assessed annually.
- Multivariate normal regression and Spearman correlations were employed for data analysis.
Main Results:
- A significant decrease in normalized plantar flexor and knee extensor strength was observed over the two-year period (P < 0.05).
- Knee extensor strength showed a larger decline compared to plantar flexor strength.
- While baseline knee extensor strength correlated with timed tests, plantar flexor strength was a stronger predictor of ambulatory function loss.
Conclusions:
- This study quantifies the progressive loss of lower limb strength in children with DMD over two years.
- The findings suggest that muscle strength alone does not fully explain the decline in functional performance.
- Compensatory strategies and other contributing factors likely play a significant role in functional deterioration in DMD.
Objective:
The main objective of this study was to examine the effect of disease on strength in two functionally important lower limb muscles for a period of 2 yrs in children with Duchene muscular dystrophy.
Design:
Seventy-seven Duchene muscular dystrophy children participated in this study. Plantar flexors, knee extensors, strength, and performance on timed tests (6-min walk, 4-stairs, 10-m walk, supine-up) were assessed yearly for 2 yrs. Multivariate normal regression was used to assess changes in strength over time in the Duchene muscular dystrophy group. Spearman correlations were computed to examine relationship between strength and function.
Results:
Normalized plantar flexor and knee extensor strength showed a significant decrease (P < 0.05) over 2 yrs, with larger declines in knee extensor. At baseline, knee extensor strongly correlated with performance on timed tests. However, plantar flexor strength was found to be a stronger predictor of loss in ambulatory function. Modest correlations (r = 0.19-0.34) were found between the decline in strength and functional performance over 2 yrs.
Conclusions:
This study describes the loss of lower limb strength in a large cohort of Duchene muscular dystrophy children for 2 yrs. The findings support that lower limb strength alone cannot account for the decline in performance on functional tests, and the role of other contributing factors, such as compensatory strategies, should be considered.
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