Muscle power, contraction velocity and functional performance after stroke

Objective: The goal of this study was to describe muscle function deficit in patients after stroke as well as to define the relationship between maximal muscle power (P_max ) and optimal shortening velocity (υ_opt ) with functional efficiency in stroke survivors.

Material and methods: A total of 134 participants were enrolled in the study, including 67 patients after a stroke and 67 volunteers, matched for age and sex (controls). Functional performance was measured with the timed Up and Go test (TUG) and additionally with Rivermead Motor Assessment (RMA) and Barthel Index (BI) in stroke survivors. To assess P_max and υ_opt of the knee extensor muscles, a specially equipped Monark cycle ergometer was used.

Results: The power generated by stroke survivors was 49.6% that of their peers and muscle contraction velocity was 65.5%. P_max /kg and υ_opt were associated with TUG outcomes in both groups. P_max /kg and υ_opt were associated with age in the control group, but not in patients after stroke. In multivariate analysis in patients after stroke, TUG was better predicted by P_max /kg or υ_opt than by the age. In stroke survivors, both P_max /kg and υ_opt were related to the BI and to the RMA total results. Both BI and RMA total were not determined by age.

Conclusions: Muscle power and muscle contraction velocity in patients who have had a stroke within three months have reduced markedly. These factors significantly affect functional performance. Muscle power and optimal shortening velocity are more important determinants of functional status than age in these stroke survivors.