Arm-trunk coordination for beyond-the-reach movements in adults with stroke.

Background. By involving additional degrees of freedom, the nervous system may preserve hand trajectories when making pointing movements with or without trunk displacement. Previous studies indicate that the potential contribution of trunk movement to hand displacement for movements made within arm reach is neutralized by appropriate compensatory shoulder and elbow rotations. For beyond-the-reach movements, compensatory coordination is attenuated after the hand peak velocity, allowing trunk movement to contribute to hand displacement. Objective. To investigate if the timing and spatial coordination of arm and trunk movements during beyond-the-reach movements is preserved in stroke. Methods. Eleven healthy control subjects and 11 individuals with mild-to-moderate chronic unilateral hemiparesis participated. Arm and trunk kinematics during 60 target reaches to an ipsilaterally placed target were recorded. In 30% of randomly chosen trials, trunk movement was unexpectedly prevented (blocked-trunk trials) by a...