Neuromuscular function deficits in older adults with MS are largely attributed to impaired neural activation without significant differences in muscle quality compared with controls.
Key Findings
Results
Older adults with MS had reduced isokinetic strength relative to body weight compared to matched controls.
Study included 10 older adults with MS and 10 age-, sex-, and BMI-matched controls.
MS participants had isokinetic strength of 0.95 N·m/kg [0.77, 1.06] compared to controls at 1.48 N·m/kg [1.23, 1.66].
Group comparisons were performed using nonparametric statistical analyses.
Participants were matched on age, sex, and BMI.
Results
Older adults with MS demonstrated reduced skeletal muscle contractile quality as measured by torque relative to muscle volume.
Summed torque relative to muscle volume was lower in MS (10.31 × 10³ N·m/cm³ [8.24 × 10³, 11.84 × 10³]) than controls (13.32 × 10³ N·m/cm³ [12.50 × 10³, 13.59 × 10³]).
Peak isometric strength relative to muscle volume was reduced in MS (0.47 N·m/cm³ [0.37, 0.51]) versus controls (0.58 N·m/cm³ [0.56, 0.63]).
Isokinetic strength relative to muscle volume was also lower in MS (0.37 N·m/cm³ [0.33, 0.42]) compared to controls (0.56 N·m/cm³ [0.52, 0.56]).
Results
Quadriceps muscle volume was similar between older adults with MS and matched controls.
MRI-derived quadriceps muscle volume in MS participants was 168.42 cm³ [158.55, 196.74].
Controls had a muscle volume of 183.26 cm³ [175.62, 202.25].
The absence of significant muscle volume differences suggests atrophy is not the primary driver of weakness in this population.
Results
Neural activation was significantly reduced in older adults with MS compared to controls.
Central activation ballistic (CAB) torque ratio was lower in MS (0.31 [0.18, 0.35]) compared to controls (0.46 [0.40, 0.57]).
Voluntary activation was reduced in MS participants (87.87% [84.09, 90.09]) relative to controls (94.82% [92.89, 95.78]).
These neural activation measures were assessed for the knee extensor muscles.
Results
No statistically significant correlations were found between neuromuscular function and MS clinical outcomes.
Clinical outcome measures were compared against neuromuscular function parameters including strength, muscle volume, and neural activation.
This finding suggests that standard MS clinical metrics may not capture the degree of neuromuscular impairment.
Methods
The study aimed to distinguish MS-related versus age-related contributions to weakness in older adults with MS by examining knee extensor voluntary activation, MRI-derived muscle volume, and skeletal muscle contractile quality.
A matched-control design was used, with controls matched on age, sex, and BMI to isolate MS-specific effects.
Nonparametric statistical analyses were employed for group comparisons.
Zhang Y, Schumacher F, Clark L, Clark B. (2026). Leg strength and neural activation deficits in older adults with multiple sclerosis.. Multiple sclerosis and related disorders. https://doi.org/10.1016/j.msard.2026.107050