Ashtanga-Based Yoga Therapy Increases the Sensory Contribution to Postural Stability in Visually-Impaired Persons at Risk for Falls as Measured by the Wii Balance Board: A Pilot Randomized Controlled Trial

OBJECTIVE: Persons with visual impairment (VI) are at greater risk for falls due to irreparable damage to visual sensory input contributing to balance. Targeted training may significantly improve postural stability by strengthening the remaining sensory systems. Here, we evaluate the Ashtanga-based Yoga Therapy (AYT) program as a multi-sensory behavioral intervention to develop postural stability in VI. DESIGN: A randomized, waitlist-controlled, single-blind clinical trial METHODS: The trial was conducted between October 2012 and December 2013. Twenty-one legally blind participants were randomized to an 8-week AYT program (n = 11, mean (SD) age = 55(17)) or waitlist control (n=10, mean (SD) age = 55(10)). AYT subjects convened for one group session at a local yoga studio with an instructor and two individual home-based practice sessions per week for a total of 8 weeks. Subjects completed outcome measures at baseline and post-8 weeks of AYT. The primary outcome, absolute Center of Pressure (COP), was derived from the Wii Balance Board (WBB), a standalone posturography device, in 4 sensory conditions: firm surface, eyes open (EO); firm surface, eyes closed (EC); foam surface, EO; and foam surface, EC. Stabilization Indices (SI) were computed from COP measures to determine the relative visual (SI(firm), SI(foam)), somatosensory (SI(EO), SI(EC)) and vestibular (SI(V), i.e., Foam(EC) vs. Firm(EO)) contributions to balance. This study was not powered to detect between group differences, so significance of pre-post changes was assessed by paired samples t-tests within each group. RESULTS: Groups were equivalent at baseline (all p > 0.05). In the AYT group, absolute COP significantly increased in the Foam(EO )(t(8) = -3.66, p = 0.01) and Foam(EC) (t(8) = -3.90, p = 0.01) conditions. Relative somatosensory SI(EO) (t(8) = -2.42, p = 0.04) and SI(EC) (t(8) = -3.96, p = 0.01), and vestibular SI(V) (t(8) = -2.47, p = 0.04) contributions to balance increased significantly. As expected, no significant changes from EO to EC conditions were found indicating an absence of visual dependency in VI. No significant pre-post changes were observed in the control group (all p > 0.05). CONCLUSIONS: These preliminary results establish the potential for AYT training to develop the remaining somatosensory and vestibular responses used to optimize postural stability in a VI population. TRIAL REGISTRATION: www.ClinicalTrials.gov NCT01366677