Ground reaction force after a sideways push as a measure of balance in recovery from stroke

Objective: To investigate if measuring ground reaction force after a sideways push at the hips gives a measure of standing balance in stroke subjects. Methods: Fifteen control subjects and 13 right hemiparetic subjects who were able to stand independently stood with their feel on a single forceplate, Horizontal sideways pushes of 3% body weight were delivered to each side of the pelvis with the subjects held firmly in a semi-rigid belt. Measurements were made of lateral pelvic displacement (sway) and the lateral sheer component of ground reaction force (GRF). Results: Right hemiparetic subjects showed significantly greater sway after a sideways push (p < 0.01) and later onset of GRF (p < 0.01) when pushed to their weak side compared with control subjects. There was also a positive correlation between sway after a sideways push and the onset latency of GRF in both strokes (0.41) and controls (0.61). The hemiparetic subjects swayed more (p < 0.01) when pushed to their weak side compared with their stronger side and their GRF latency was longer, but this latter measurement failed to reach statistical significance. No difference was seen between sides in sway or GRF latency in controls. Conclusions: The latency of GRF onset after a push at the hips in controls and in stroke subjects is related to sway and both measurements increase after a stroke. This test offers a method of measuring balance after a stroke, and serial testing of an individual after a stroke may prove a useful measure of an individual's recovery of balance.