How visual feedback of decomposed movements of the center of pressure trajectories affects undisturbed postural control of healthy individuals.

The center-of-pressure (CP) trajectory is a complex movement comprising both the vertically projected displacements of the centre-of-gravity (CG(v)) and the CP - CG(v) differences whose magnitudes are proportional to the horizontal accelerations communicated to the CG. One may, therefore, investigate whether the information given by these movements can be differentially used for controlling the standing posture. To this aim, a group of healthy adults was tested through four conditions including visual feedback (VFB) of their CP in real time and, with a 578 ms delay, CP, CG(v) and CP - CG(v) movements. The CG(v) and, thus, CP - C G, movements, were implemented from a numerical filter applied to the CP displacements. The postural behavior was assessed on the basis of basic CG(v) and CP - CG(v) movements estimated from the CP trajectories. The postural behavior observed during delayed CG(v) feedback was similar to the one observed with the similarly delayed CP movements feedback. On the other hand, the delayed CP - CG(v) feedback infers a decrease of the CP - CG(v) movements and concomitantly an increase of the CG(v) movements. This data highlight that there is enough information in the displayed CP trajectories to enable control of the CG and that providing CP - CG(v) information can lead the subjects to solely decrease these movements.