Muscle strength and stiffness of elbow muscles: correlation with upper limb motor functions in people with chronic stroke.

Abstract

To (i) quantify elbow flexor and extensor strength and stiffness in people with stroke; (ii) compare affected and unaffected sides; (iii) compare stroke survivors and healthy older adults; and (iv) examine correlations between muscle properties, motor control, and ADLs. Cross-sectional study. 65 stroke survivors and 31 healthy older adults. Elbow muscle strength and stiffness (biceps and triceps) were assessed bilaterally by Myoton PRO. Stroke participants also completed the Fugl-Meyer Assessment-Upper Extremity (FMA-UE), Action Research Arm Test (ARAT), Disabilities of the Arm, Shoulder and Hand (DASH), and Oxford Participation and Activity Questionnaire (OxPAQ). Stroke participants had significantly weaker elbow muscles on the affected side (p < 0.001) than the unaffected side, but stiffness did not differ significantly. Compared with healthy adults, stroke participants showed reduced strength but similar stiffness. Weak to moderate correlations were found between muscle strength and FMA-UE, ARAT, and DASH (ρ = 0.336-0.613), but not with OxPAQ. Weak negative correlations were found between biceps stiffness and motor function (FMA, ARAT) (ρ = -0.343 to -0.397), and a weak negative correlation between triceps stiffness and OxPAQ emotional well-being (ρ = -0.313). Stroke survivors have reduced elbow strength but similar stiffness compared with the healthy elderly. Strength correlates moderately with upper limb function; stiffness shows inconsistent associations.