Relation between postural control assessment with eyes open and centre of pressure visual feedback effects in healthy individuals.

Visual feedback (VFB) of the resultant centre of pressure (CP(Res)) is a potentially interesting technique for rehabilitation purposes. However, all past studies have not been unanimous in supporting its utility in a physical therapy program. The present study was therefore undertaken with the main aim of assessing whether insights from postural control without additional feedback could be gained to explain the possible VFB effects. The CP(Res) displacements of 65 healthy adults were analysed in two conditions (eyes-open and VFB) through various classical parameters (including surface and variances along each medio-lateral and antero-posterior axes) and fractional Brownian motion (fBm) modelling. The results indicate that 69% of the sample were dependent on VFB, i.e. that the surface covered by the CP(Res) displacements was smaller during VFB than in the eyes-open condition. The comparison of the two subgroups (i.e. those who were dependant on VFB and those who were not) brought out significant differences in many classical and fBm parameters. In addition, the correlation between the degree of VFB dependency and the values measured during the eyes-open condition indicates that the more the subjects are VFB-dependent, the less they lean forward, the smaller the variance and the better the CP(Res) displacements are controlled over the longest time intervals. By specifying the links between the postural performance in an eyes-open standard condition and the degree of VFB dependency, a number of clues help identify the reasons for which some subjects do not succeed in using this technique, hence explaining the controversy about its use as a rehabilitation tool.