Fingertip touch adjust postural orientation during perturbed stance

Abstract

Additional sensory information; especially from touch, was suggested to improve stability by reducing body sway. However, it is less known about the effect of touch on the body’s joint movement during perturbed standing; which is commonly experienced by public transport users. In this study, subjects were asked to try to maintain their standing position with their fingertips on a rigid surface, while surface perturbation was applied at four different perturbation frequencies (0.2, 0.4, 0.6, and 0.6 Hz) and different vision input. Motion of joint (ankle, hip and head) and relative centre of mass (COM) were recorded and analysed. The results show that fingertip pressure was higher without vision. Furthermore, different fingertip moment directions were recorded between with vision and with no vision. This possibly indicates a preferred fingertip position that can provide better sensory information to replace sensory loss; especially vision. The range of motion of joints also decreased with fingertip touch-except for head motion. Furthermore, even though there were no significant differences observed between with touch and without touch, the relative COM displacement was less with touch. Thus, even with a very light touch, subjects were able to reduce body sway even in a perturbed stance. Further investigation is needed to determine the changes in centre of pressure (COP) and significant position of fingertip, which can enhance stability.