Weight distribution in standing and sitting positions, and weight transfer during reaching tasks, in seated stroke subjects and healthy subjects

The recovery of sitting balance after a stroke is assumed to be essential to obtain independence in other vital functions. The purpose of the present study was to investigate weight distribution while sitting and standing still, and weight transfer during seated reaching tasks performed by stroke subjects and healthy subjects.

The study was cross-sectional. Twenty-one stroke subjects and 21 healthy subjects, matched by age and gender, participated. Main measures were weight distribution while standing and sitting still, and displacements of centre ofpressure (COP) during seated reaching tasks. Data were collected using a balance performance monitor (BPM), including software.

Stroke subjects had less symmetrical weight distribution in standing than that of healthy subjects (p < 0.001). No significant differences between the groups were found while sitting still, and no associations between asymmetries in standing still and sitting positions within individual stroke subjects were found. Neither did the degree of weight distribution in sitting correspond to COP displacements in seated reaching tasks. However, COP displacement patterns in reaching tasks in the seated position were different in stroke subjects from those of healthy subjects. Stroke subjects showed more lateral displacement when reaching forwards (p < 0.001), and less lateral displacement when reaching sideways to the unaffected side (p = 0.01).

COP displacement patterns in stroke subjects deviate more than those of healthy subjects in seated reaching tasks. The deviating COP displacement patterns are discussed as a possible dysfunction in the ability to make postural adjustments and learn an efficient movement pattern.