Enhancing Human Balance Control by Apply Random Vibrations to the Ankle Tendons

Abstract

Somatosensory function declines with age, and such changes have been associated with postural instability. Recently, it has been shown that input noise can enhance sensory and motor function. PURPOSE: The goal of this study was to investigate whether subsensory mechanical noise applied to the ankles via randomly vibrating wraps can be used to improve balance control in young and elderly subjects. METHODS: Two quiet standing experiments were performed. Experiment 1 investigated the application of four different amplitudes of noise to find the noise level that produced the largest reduction in postural sway in twelve healthy young subjects. Experiment 2 tested further the effect of this optimal noise level on balance control in a sample of fifteen healthy young and fifteen healthy elderly subjects. To characterize balance during quiet standing, five traditional sway parameters, five sway parameters that have been shown to be predictive of falls, and three random-walk sway parameters were computed for the noise and control (no noise) trials, respectively, for each subject. RESULTS: In Experiment 1, four of the five traditional sway parameters indicated that the optimal level of mechanical noise was 75% of the sensory threshold for the subjects tested. In Experiment 2, application of this optimal level of noise (75% of sensory threshold) resulted in a reduction in 12 of the 13 sway parameters in the young subjects and all of the sway parameters in the elderly subjects. For the main effect of stimulation, decreases in 10 of the sway parameters– five traditional, three fall-predictive, and two random-walk parameters-were statistically significant (p <0.05). The elderly subjects also showed greater improvements than the young in the anteroposterior range of sway (p= 0.047). CONCLUSION: These findings suggest that noise-based devices, such as randomly vibrating ankle wraps, could ameliorate age-related impairments in balance control. Supported by NIH Grant HD37880, AG08812 andHD40035.