The purpose of this study was to test the hypothesis that imposing weight shift onto the lower extremity of standing hemiparetic patients improves participation of its muscles in postural tasks. Subjects were seven hemiparetic stroke patients and five healthy controls. Each subject performed one static and two dynamic postural tasks, once with both lower extremities on a level surface and once with the intact lower extremity (patients) or either foot (normals) on a step. Dependent variables were bilateral electromyographic (EMG) recordings of the medial gastrocnemius, tibialis anterior, and gluteus medius muscles. The anterior-posterior reaction moment was used to delimit the dynamic tasks. Despite substantial loading of the affected lower extremity, the results failed to demonstrate a beneficial contribution to the timing or to the amount of EMG activation of the monitored muscles. Rather, loading of the paretic leg only seemed to increase extensor synergy or activation of the medial gastrocnemius muscle.
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