Development of a Position-Specific Index of Muscle Strength to be Used in Stroke Evaluation

Moriello C, Mayo NE. Development of a position-specific index of muscle strength to be used in stroke evaluation.ObjectiveTo develop a position-specific index of muscle strength for individuals with stroke.DesignCross-sectional design.SettingA major teaching hospital in a Canadian urban city.ParticipantsSixty-three patients with poststroke onset between 3 and 12 months.InterventionsNot applicable.Main Outcome MeasureThe muscle strength of the lower-extremity muscles was tested bilaterally in multiple positions using hand-held dynamometry.ResultsA principal components analysis resulted in grouping the muscles of the affected and unaffected sides of the gravity related and gravity eliminated positions into 5 indices. The 5 indices were moderately to highly correlated (r2 range, .59−.81) with each other and so were combined into 1 global index. The gravity related muscle strength on the affected side was, on average, 85% of the unaffected side (range, 37%–157%); the gravity eliminated muscle strength of the affected side was, on average, 92% of the unaffected side (range, 53%–121%).ConclusionsThis study resolves the methodologic issue of how to summarize multiple data points that relate to one construct, namely, strength of different muscle groups assessed in several positions.