Performance in the stability limits test during rehabilitation following stroke

The extent to which the standing posture could be perturbed voluntarily by having the subject displace the centre of pressure (CP) to the outer limits of the base of support was investigated in 20 stroke patients who were undertaking inpatient rehabilitation and 20 control subjects matched by gender and age. The mean age of the stroke patients was 50.7 years (S.D. = 18.5) and testing occurred after a median of 10 weeks post-onset. A force platform was used to quantify displacement of the CP in the forward and backward directions and laterally to each leg during sustained weight-shifting. The distribution of weight between the legs was also quantified during standing and antero-posterior (AP) weight-shifting by measuring the mean position of the CP in the lateral axis. Compared to controls, the stroke patients showed deficits in weight-shifting in both forward (P < 0.01) and backward (P < 0.01) directions. Forward displacement was greater than backward displacement in both groups (P < 0.01). During standing and AP weight-shifting stroke patients deviated from the mid-line of the base of support more than the control subjects, however the deviation was not always towards the unaffected leg. Compared to control subjects the stroke patients had significant deficits in the ability to weight-shift in the lateral direction to both legs. Although the stroke patients showed a trend for less displacement to the affected leg than the unaffected leg, this difference was not greater than the comparable difference in control subjects. The true ability to weight-shift to the unaffected leg may have been masked because of the testing protocol. For this reason modifications are required to the testing protocol. These findings from stroke patients in the early stage post-onset provide objective data on which to base treatment strategies during rehabilitation.