Kinematic Manifestation of Arm-Trunk Performance during Symmetric Bilateral Reaching after Stroke: Within vs. beyond Arm's Length

Objective The aim of this study was to examine the effect of target distance (within vs. beyond arm's length) on arm and trunk movements during symmetric bilateral reaching in patients with stroke. Design Eighteen stroke patients and 18 age-matched control participants reached bilaterally to press desk bells placed at 90% and 125% of arm's length. The kinematics of paretic arm and trunk movements and trunk contribution slopes were measured in the start, mid, and end phases of reaching. Results Target distance significantly affected arm (shoulder flexion and abduction, elbow extension) and trunk (flexion, rotation, and lateral shift) movements in patients with stroke. Significant group differences were also found in trunk contribution slopes in the start and mid phases of reaching to targets beyond arm's length. Conclusions Bilateral reaching for targets beyond arm's length may increase shoulder flexion, shoulder abduction, elbow extension, and trunk flexion, but it may also induce unsymmetric trunk rotation and lateral shift to the paretic side, as well as early and excessive trunk contributions in patients with stroke. The findings suggest that for beyond-Arm-length reaching, therapists may restrain the trunk until the end phase of reaching and prevent trunk rotation and lateral shift to the paretic side.