Effect of Subsensory Vibration on Postural Control of Healthy Elderly and Subjects with Simulated Reduced Plantar Feet Sensation: A Randomized Crossover Controlled Trial

Abstract Introduction Postural instability is considered a normal result of aging and is caused by some diseases such as neuropathy. Aim The purpose of the present study was to analyze and compare the effect of subthreshold vibration that was applied to the plantar surface of feet on balance control of healthy elderly and young subjects with simulated decreased plantar feet sensation. Methods Twenty-four subjects (12 elderly persons and 12 young persons with decreased plantar feet sensation) were included in this randomized, double-blinded crossover study. Participants were divided into two intervention groups: 1) orthopedic shoe with vibration mechanism on; and 2) orthopedic shoe with vibration off. Primary outcomes were center of pressure (COP) parameters including mean velocity, phase plane portrait, standard deviation (SD) of amplitude, and SD of velocity. Secondary outcomes were Berg Balance Scale (BBS) score and timed up and go test (TUG). The standing balance was tested with different conditions: eye opened/closed and foam/rigid surface. General linear mixed models tests were used for statistical analysis. The level of statistical significance was set at 0.05 for all analyses. Discussion This study showed very large effect sizes (partial η 2 > 0.2) with application of vibration as compared with vibration off for COP parameters with greater effects in condition with more baseline fluctuations. There was significant change in BBS test (Cohen d , 0.6; confidence interval [CI], −0.215 to −1.421). The time on TUG test was decreased and approached significance ( P = 0.06). Conclusions The immediate effect of the study showed that subthreshold vibration can improve static and dynamic balance in healthy elderly people and people with decreased plantar feet sensation. However, long-term studies are needed to establish the clinical value of the subthreshold vibration on balance control. Clinical Relevance Subthreshold vibration applied to the feet soles via custom-made shoes can reduce the postural sway in subjects with decreased feet sensation. By conducting more studies with conclusive results in the field of vibration effectiveness in the elderly, we can hope to reduce the rate of falls in the elderly.