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-CG_v 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