Control of paretic and non-paretic upper extremity during bimanual reaching after stroke

Most actions of daily life engage the two upper extremities (UEs) in a highly coordinated manner. While it is recognized that bimanual movements are impaired post-stroke, understanding how the paretic and non-paretic UE contributes to this impairment is important for future interventions. We investigated kinetic and kinematics at the shoulder, elbow, and wrist joints in the paretic and non-paretic UE in 8 individuals with chronic stroke and non-dominant UE in 8 healthy controls during unimanual and bimanual tasks. Kinematic analysis revealed little effect of stroke. However, kinetic analysis revealed that during unimanual movements, joint control was impaired during unimanual and bimanual movements in both UEs, although to a lesser extent in the non-paretic than paretic UE. During bimanual movements, joint control did not change in the paretic UE, and it further deteriorated in the non-paretic UE compared with the unimanual movements. Our findings suggest that a single session of bimanual task performance does not improve joint control of the paretic UE and it impairs control of the non-paretic UE, making it more like that of the paretic UE.