Effect of Haptic Supplementation Provided by a Fixed or Mobile Stick on Postural Stabilization in Elderly People

Abstract

Background: Haptic supplementation by a light touch with the index finger on a stable surface has been widely shown to increase postural stability. With a view to a potential application in the domain of mobility aids, it should, however, be demonstrated that haptic supplementation is effective even if provided by a mobile support. Objective: The present experiment aimed at determining whether haptic supplementation was effective in elderly people when provided by a light grip on an unstable stick support. Methods: Ten young and 11 older adults were tested in an upright position in 6 experimental conditions, in which the mobility of the stick support and its resistance to body sway were manipulated. Classical center-of-pressure (COP) variables (i.e. root mean square variability, range and area) were computed together with power spectral analysis and stabilogram diffusion analysis (SDA) variables of COP. Results: The results suggest that the stabilizing effect of haptic supplementation is independent of age and the nature of the support (fixed or mobile) when transient sway-related contact forces at the fingertip and proprioceptive cues are of sufficient magnitude. The results also indicate that haptic supplementation attenuates the age-related increase in energy consumption during the postural task even in the mobile support condition on a low-resistance surface. The results of SDA suggest that the availability of sway-related haptic cues reduces reliance on increased muscle activity around the ankle over short time intervals of postural control. After some time, haptic supplementation eventually leads to well-coordinated postural corrections. Conclusions: In summary, haptic supplementation improves postural control mechanisms independent of age due to enhanced perception of self-motion through sensory interaction with the environment.