Visual feedback of force platform displacements for balance control training: what postural ability do healthy subjects have to develop to decrease the difference between center of pressure and center of gravity movements?

Past studies have emphasized the beneficial effect of additional visual feedback (VFB) on the capacity of healthy adults to decrease the amplitudes of the center-of-pressure minus center-of-gravity (CP-CG(v)) movements. To better assess these capacities, 56 subjects were asked to stand still on a force platform and to use the visual information provided. Dependency coefficients, based on their capacity to lower their CP-CG(v) movements and therefore relax their lower limb muscles, as well as parameters aimed at characterizing their postural strategies were measured across VFB conditions including (1) CP displacements in real time (VFB(CP0)), (2) CP displacements with a 600-ms delay (VFB(CP600)), and (3) CP-CG(v) displacements with a 600-ms delay (VFB(CP-CG600)). A non-VFB condition (eyes open) was also included. Several linear correlations were used to specify the relation between subjects' capacity to relax, compared with the VFB(CP0) condition, across the three remaining conditions. The data highlight the complementary nature of the VFB conditions and establish the postural control behaviors necessary to use these VFB protocols efficiently.