The Effects of a Plantar Pressure-Based, Tongue-Placed Tactile Biofeedback System on the Regulation of the Centre of Foot Pressure Displacements During Upright Quiet Standing: A Fractional Brownian Motion Analysis

A biofeedback system whose underlying principle consists in supplying the user with supplementary sensory information related to foot sole pressure distribution through a tongue-placed tactile output device was recently developed for improving balance. The purpose of this study was to unravel the underlying control mechanisms involved in the regulation of the centre of foot pressure (CoP) displacements during upright quiet standing with this biofeedback system. Ten young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. CoP displacements, recorded using a force platform, were processed through a space-time domain analysis and modeled as fractional Brownian motions according to the procedure of stabilogram-diffusion analysis (SDA). The space-time domain analysis showed decreased CoP displacements in the Biofeedback relative to No-biofeedback condition. Complementary, the SDA showed decreased spatiotemporal threshold at which corrective mechanisms are called into play and an increased degree of control of the CoP displacements in the Biofeedback relative to No-biofeedback condition. The present findings evidence that the effectiveness of the biofeedback in decreasing the CoP displacements during upright quiet standing stems from an increased contribution and efficiency of anti-persistent mechanisms (feedback control) involved in the regulation of the CoP displacements.