Vibrotactile Feedback for Improving Standing Balance

Abstract

Maintaining balance standing upright is an active process that complements the stabilizing properties of muscle stiffness with feedback control driven by independent sensory channels: proprioceptive, visual, and vestibular. Considering that the contribution of these channels is additive, we investigated to what extent providing an additional channel, based on vibrotactile stimulation, may improve balance control. This study focused only on healthy young participants for evaluating the effects of different encoding methods and the importance of the informational content. We built a device that provides a vibrotactile feedback using two vibration motors placed on the anterior and posterior part of the body, at the L5 level. The vibration was synchronized with an accelerometric measurement encoding a combination of the position and acceleration of the body center of mass in the anterior-posterior direction. The goal was to investigate the efficacy of the information encoded by this feedback in modifying postural patterns, comparing, in particular, two different encoding methods: vibration always on and vibration with a dead zone, i.e., silent in a region around the natural stance posture. We also studied if after the exposure, the participants modified their normal oscillation patterns, i.e., if there were after effects. Finally, we investigated if these effects depended on the informational content of the feedback, introducing trials with vibration unrelated to the actual postural oscillations (sham feedback). Twenty-four participants were asked to stand still with their eyes closed, alternating trials with and without vibrotactile feedback: nine were tested with vibration always on and sham feedback, fifteen with dead zone feedback. The results show that synchronized vibrotactile feedback reduces significantly the sway amplitude while increasing the frequency in anterior-posterior and medial-lateral directions. The two encoding methods had no different effects of reducing the amount of postural sway during exposure to vibration, however only the dead-zone feedback led to short-term after effects. The presence of sham vibration, instead, increased the sway amplitude, highlighting the importance of the encoded information.

Integrating Tactile Feedback Technologies Into Home-Based Telerehabilitation: Opportunities and Challenges in Light of COVID-19 Pandemic

“…The feedback provided by some common devices might be difficult to interpret and integrate. Also, the tactile stimuli patterns might not be intuitive or might be too complex for the user, due to either the number of tactile motors forcing the user to process a redundant set of signals, or to the encoding methods that may require specific attention (Brewster and Brown, 2004 ; Ballardini et al, 2020 ). This is especially important for patients undergoing rehabilitation training, who are often at the initial stages of learning that already require a relatively high degree of cognitive effort and attention (Fitts and Posner, 1967 ).…”

“…Typically, the actuators used in wearable devices produce vibration at frequencies above 100 Hz, which activates the Pacinian corpuscles mechanoreceptors (Culbertson et al, 2018b ). The most common locations for applying the vibrotactile stimulation are the arm (Bark et al, 2008 ; Huisman et al, 2013 ; Krueger et al, 2017 ; Shah et al, 2018 ; Risi et al, 2019 ) and the torso (Van Erp et al, 2005 ; Lee et al, 2012 ; Ballardini et al, 2020 ). Other locations for stimulation include the hand (Jiang et al, 2009 ; Wan et al, 2016 ) and different locations on the lower limb (Chen B. et al, 2016 ; Shi et al, 2019 ).…”

“…Results from a meta-analysis indicated that vibrotactile feedback was effective in reducing task completion times, but neither forces nor errors were significantly reduced (Nitsch and Färber, 2012 ). In addition, vibration feedback encoding center of mass or center of pressure motion was used to improve standing balance (Lee et al, 2012 ; Ma and Lee, 2017 ; Ballardini et al, 2020 ) and walking patterns (Janssen et al, 2009 ; Muijzer-Witteveen et al, 2017 ; Xu et al, 2017 ). Vibrotactile feedback based on stochastic resonance was applied for improving visuomotor temporal integration in hand control (Nobusako et al, 2019 ) and balance control (Magalhães and Kohn, 2011 ).…”

Vibrotactile-Based Rehabilitation on Balance and Gait in Patients with Neurological Diseases: A Systematic Review and Metanalysis

“…In most studies, the vibrotactile vibrating motors were applied at the lower back level, probably because of the proximity with the center of mass (COM) position during quiet standing [ 56 ]. Moreover, this area provides a large, readily accessible surface with a relatively uniform shape that can be conveniently used to accommodate the vibrotactile device [ 57 ].…”

“…Additionally, with respect to the type of device used, it is not possible to define a preferability, as eight studies used vibrotactile effectors of different shapes and sizes, self-produced or unspecified devices [ 34 , 42 , 50 , 51 , 52 , 54 , 55 , 56 ]. The commercial vibrotactile devices used were: WEARHAP-Pd device [ 32 ]; SBS (Smarter Balance System) [ 45 ]; Sensory Kinetic System [ 44 ]; UpRight [ 43 ]; Balance Freedom [ 41 ]; Vibrotactile circuit C2 tractors (Engineering Acoustic Inc.) [ 46 , 47 ]; Vibrotactile NFT and Vertiguard-RT [ 48 ] Vertiguard training device [ 49 ].…”