Comparing different visual biofeedbacks in static posturography

Several studies have showed the positive effect that real-time presentation of centre of pressure (COP) has on stability. Typically the COP position is depicted in real-time on the screen and it is required that the participant uses this additional information to regulate his/her postural sway. In order to perform the motor task, it requires an attentional load that influences the postural performance. Up-to now no study has focused on the effect that modality of VBF presentation could have on postural control and how it depends on the attentional load needed. Goal of this study was to compare the effects that two different modalities of Visual Biofeedback (VBF) presentation, which require different focus of attention, could have on postural stability. The CoP coordinates were extracted from force plate data and elaborated in real-time to implement two VBFs: VBFsquare, where the CoP is shown on a screen together with a square stability area, extracted from anthropometric feature; and VBFsmile, which let the participants know if they are or are not in the stability area by an emoticon image. Two groups of twelve healthy young subjects executed the protocol in two different sequences composed of the following conditions: noVBF-VBFsquare and noVBF-VBFsmile. Each condition was repeated three times. The effect of the two VBFs was studied by four parameters extracted directly from CoP coordinates (sway area, sway path, mean amplitude and mean frequency). The comparison between the two VBFs showed significant difference in sway path and mean frequency. The decrease of the parameters' values in VBFsmile opens the possibility of using it as a tool to facilitate postural control in upright stance.