The effect of a textured insole on anticipatory postural adjustments

Abstract

Purpose To obtain preliminary data on the effect of a textured insole on postural control. Methods Nine healthy subjects were exposed to external perturbations applied to their shoulders while standing with or without a single textured insole. Body weight distribution and bilateral electromyographic activity (EMG) of trunk and leg muscles were recorded. Onsets of EMG activity of muscles were calculated and analyzed within the interval typical for anticipatory postural adjustments. Results When a textured insole was provided under one foot, subjects shifted their body weight towards the contralateral foot. With no insole, the anticipatory onsets of EMG activity of the left and right muscles were symmetrical; when a textured insole was used, the EMG onsets of the muscles on the contralateral side of the body were seen earlier as compared to the insole side. This early activation was more pronounced in the trunk muscles (p < 0.05). Conclusions Using a single textured insole under one-foot induced asymmetry of anticipatory onsets of EMG activity in healthy subjects. The outcome highlights the importance of investigating the role of a single textured insole in control of vertical posture and provides a foundation for future studies focussed on improvement of postural control in individuals with body asymmetry due to unilateral weakness.