Task directionality impacts the ability of individuals with chronic hemiparetic stroke to match torques between arms

Abstract

Post hemiparetic stroke an individual may face difficulty performing bimanual tasks due to an asymmetry in their arms' strengths. Here, we determined whether participants with a strength asymmetry were impaired bi-directionally when matching torques between arms (i.e., paretic arm matches non-paretic arm, non-paretic arm matches paretic arm). Six participants with chronic hemiparetic stroke and four participants without neurological impairments partook in this study. First, we identified the maximum voluntary torque that participants could generate about each elbow joint (τ_mvt). Then, we determined how accurately and precisely participants could match, bidirectionally, submaximal isometric flexion torques (0.25 · τ_{MVT:Reference}) between arms. Results demonstrate that task directionality impacted the ability of our participants with stroke who had a strength asymmetry to match torques between arms; specifically, participants were unimpaired matching to a referenced non-paretic arm yet impaired in the opposite direction. Additionally, results reveal that the degree to which participants overshot the target torque when matching with their non-paretic arm could be predicted based on their strength asymmetry (R² _Adjusted = 0.67). We propose that individuals with stroke may avoid torque matching impairments during bimanual tasks by matching their paretic arm to their non-paretic arm.