Exploiting interlimb coupling to improve paretic arm reaching performance in people with chronic stroke

Objective: To determine whether paretic arm reaching performance is improved in bilateral compared with unilateral conditions. Design: Cohort study. Setting: University human performance laboratory. Participants: Thirty-two subjects with chronic stroke (57+/-14y; on Fugl-Meyer Assessment arm score, 37+/-14). Intervention: Unilateral and bilateral reaching. Bilateral tasks included varying levels of weight on the nonparetic hand. Main Outcome Measures: An electromagnetic tracking system recorded hand peak acceleration, velocity, and movement time. A 2-way repeated-measures analysis of variance and Tukey-adjusted pairwise comparisons were used to analyze the results (alpha=.05). Results: Paretic differed significantly from nonparetic peak acceleration and velocity in unilateral reaching but not bilateral reaching. Within limbs, the paretic arm attained a higher peak acceleration (P<001) and velocity (P=.03) in the bilateral compared with the unilateral task, but movement time was unchanged between tasks. Nonparetic peak acceleration was higher (P=.015), velocity was unchanged, and movement time increased (P=.005) in the bilateral compared with the unilateral task. The addition of a weight to the nonparetic arm during bilateral reaching did not result in further improvement in paretic arm performance. Conclusions: Interlimb coupling effects during bilateral reaching are retained even after chronic stroke and can be used to produce an immediate improvement in paretic arm reaching performance.