Effect of haptic supplementation on postural stabilization: A comparison of fixed and mobile support conditions

International audienceIt is well known in the literature of haptic supplementation that a "light touch" (LT) with the index finger on a stable surface increases postural stability. In view of potential application in the domain of mobility aids, it should however be demonstrated that haptic supplementation is effective even when provided by an unstable stick support. The present study aimed to explore the stabilizing effect of a three-digit "light grip" (LG) of different supports (fixed or mobile stick) in young people. Eleven participants (M = 25.9 years) were tested in an upright standing task in six experimental conditions in which the mobility of the given support and its resistance in opposite direction to the body movement were manipulated. The RMS variability and the range of postural oscillations were measured. The results confirmed that the stabilizing effect of haptic supplementation is independent from the nature of the support (fixed or mobile) when sufficiently large sway-related contact forces on the fingers are provided. Future applications of this "mobile stick paradigm" to complex situations while targeting different groups of participants may help to approach everyday life situations in which an informational stick could potentially be of assistance to gain stability and mobility

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

International audienceBackground: 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. Copyright (C) 2012 S. Karger AG, Base

Effect of haptic supplementation on postural control of younger and older adults in an unstable sitting task

International audienceStanding postural control is known to be altered during aging, but age-related changes in sitting postural control have scarcely been explored. The present experiment studied the roles of visual and haptic information in a sitting task in both young and older adults. Fifteen young and fifteen older adults participated in this study. Six experimental conditions were performed with eyes open and eyes closed: quiet sitting, rocker-board sitting, and 4 conditions of haptic supplementation, provided by a hand-held pen, during rocker-board sitting. Classical variables were extracted from the center of pressure (COP) and pen trajectories, and the stabilogram diffusion analysis was performed on the COP data. Three-way ANOVAs (Group x Vision x Condition) were carried out. Postural instability was strongly attenuated by haptic supplementation in both age groups. Furthermore, instability due to visual deprivation was compensated by haptic supplementation. Long-and short-term diffusion coefficients were smaller in conditions of haptic supplementation. The present study confirmed the effect of haptic supplementation on both open-loop and closed-loop mechanisms of postural control and extended it to unstable sitting in young and older adults despite the complex biomechanical systems involved in sitting postural tasks. (C) 2014 Elsevier Ltd. All rights reserved