Maximal voluntary isometric elbow flexion force during unilateral versus bilateral contractions in individuals with chronic stroke

The purpose of this study was to determine whether the phenomenon of bilateral deficit in muscular force production observed in healthy subjects and mildly impaired stroke patients also exists in patients with more chronic and greater levels of stroke impairment. Ten patients with chronic hemiparesis resulting from stroke performed unilateral and bilateral maximal voluntary isometric contractions of the elbow flexors. When the total force produced by both arms was compared, 12% less force was produced in the bilateral compared with unilateral condition (p=0.01). However, studying the effect of task conditions on each arm separately revealed a significant decline in nonparetic (p=0.01) but not paretic elbow flexor force in the bilateral compared with unilateral condition. Results suggest that a significant bilateral force deficit exists in the nonparetic but not the paretic arm in individuals with chronic stroke. Bilateral task conditions do not seem to benefit or impair paretic arm maximal isometric force production in individuals with moderate-severity chronic stroke.