Title: The Effects of Cutaneous Vibration on Dynamic Balance Control
Supervisor: Dr. Mark Carpenter
Committee member: Dr. Romeo Chua, Dr. Timothy Inglis
Abstract: Falls are the leading cause of injury for older adults in Canada and often occur in dynamic conditions when individuals fail to recover from unexpected balance disturbances, emphasizing the importance of reactive balance control. Subthreshold vibratory noise applied to the foot sole has been shown to improve static balance across multiple populations (younger and older adults, individuals with diabetic neuropathy, arthritis, or amputation), but its effects on dynamic balance and at more proximal sites of the body remain unknown. This thesis will test whether subthreshold vibration applied at the ankle, hip, or both improves reactive balance control during transient and continuous support surface translations. Twenty healthy young adults will stand barefoot with eyes closed. Stimulation intensity will be set to 90% of each participant’s perceptual threshold. Vibration conditions will be presented in pseudorandom order with participant blinding. Transient trials will require recovering balance without stepping in response to backward translations, with approximately 20% forward catch trials, for a total of 60 trials. Continuous trials will include 12 perturbations lasting 30 seconds using a pseudorandom sum-of-sines signal composed of 0.3 to 0.6 Hz waves. Surface electromyography will provide onset latencies and amplitudes of balance correcting responses. Body-worn motion capture sensors will collect kinematics to quantify mechanical stability using the margin of stability measure. Outcomes will be tested for main effects of frequency and location. We hypothesize that subsensory vibration, especially combined ankle and hip stimulation, will decrease muscle onset latencies, increase response amplitudes, and enlarge the margin of stability, indicating improved dynamic stability in young adults. This work may inform future studies in more vulnerable populations.