Effects of visual center of pressure feedback on postural control in young and elderly healthy adults and in stroke patients.

The goal of this study was to compare young and elderly healthy individuals and elderly stroke patients in their capacity to use visual CP feedback (VF) in controlling both quiet standing and weight shifting and to assess their sensory re-weighing when this VF is withdrawn. A total of 40 participants were involved in this study. Participants were asked to either quietly stand on a force platform for a period of 45 s with eyes open (EO), using visual feedback (VF) or without visual feedback (No VF) or to perform a dynamic weight shifting task while using VF or No VF. During the quiet standing trials with VF, only the young (YO) were able to decrease the amplitude and increase the frequency of their sway in either plane. Removal of the VF resulted in a 'destabilizing' effect in both healthy elderly (EL) and stroke patients (ST) in the sagittal plane. With regard to the dynamic task, both the YO and EL were generally more successful at weight shifting in terms of speed and control when compared to the ST. Yet, when VF was removed, only the YO were able to largely maintain speed and precision of control. Hence, providing or removing visual CP feedback during quiet standing or removing VF during visually controlled weight shifting can discriminate healthy young participants from healthy elderly, but does not clearly discriminate healthy elderly from stroke patients in the same age group. Results revealed that sagittal plane imbalance in healthy elderly and stroke patients may be largely due to the effects of aging, whereas frontal plane imbalance is much more specific for the postural problems associated with stroke.