Relationship between active range of motion deficits and muscle strength and tone at the elbow in patients with hemiparesis

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Abstract
The purpose of this study was to describe the relationship between deficits in active range of motion (ROM) at the elbow and both agonist muscle strength and antagonist muscle tone in patients with stroke. Twenty-three patients with non-flaccid hemiparesis participated. Active elbow flexion and extension ROM were measured gravity eliminated bilaterally and ROM deficits were calculated for the paretic side. Isometric elbow flexion and extension strength were measured on the paretic side using a hand-held dynamometer. Elbow flexor and extensor muscle tone were graded manually using the Modified Ashworth Scale. The Spearman correlations between active elbow flexion ROM deficits and elbow flexion force, and between active elbow extension ROM deficits and elbow extension force were -.929 and -.772 respectively. The correlations between the elbow flexion ROM deficits and elbow extensor muscle tone, and between the elbow extension ROM deficits and elbow flexor muscle tone were .287 and .480 respectively. Regression analysis revealed a curvilinear relationship between active elbow flexion ROM deficits and elbow flexion force (R =.881), and a linear relationship between active elbow extension ROM deficits and elbow extension force (R = .771). In patients like those tested, agonist muscle force (strength) may be more important than passive antagonist restraint (tone) as a determinant of ROM deficits. Because a limited amount of muscle force is required for full active ROM, increases in muscle strength beyond some threshold will not be accompanied by further improvements in active ROM.