Reaching-lifting-placing task during standing after stroke: Coordination among ground forces, ankle muscle activity,...

To investigate the coordination among hand movement, ground forces, and muscle activity in standing stroke patients reaching forward and lifting an object from a table.

Survey.

Research laboratory.

Eight stroke patients and 8 persons serving as controls.

Symmetry of percentage of body weight (BW) during initial standing, velocity and hand path trajectory, ankle muscle electromyography. Temporal and spatial parameters in percentage of movement time were recorded by using 2 forceplates, 3-dimensional kinematics, and surface electromyography. Motor function, sensory function, and functional performance were also assessed.

Weight distribution during initial standing was significantly higher (57.4% +/- 8.1% BW) on the nonparetic leg. All subjects had preserved the preparatory loading phase, and after onset of hand movement loading shifted to the contralateral leg. Ankle muscle activity onset (lateral gastrocnemius [LG]) occurred after loading. In stroke subjects, LG was consistently activated first in the nonparetic leg, regardless of which arm performed the task. During paretic hand task, the reaching phase was significantly longer and the lifting phase significantly shorter compared with that of the nonparetic hand task and with that of the controls. In the paretic task, the hand path velocity was not bell-shaped; the object lifting was.

Stroke subjects preserve the coordination between ground forces and hand movement. The lack of spontaneous use of the paretic hand is primarily caused by difficulties of planning the hand trajectory in space, as reflected by temporal and spatial parameters during task performance.