Frequency-dependent effects of hip abductor vibration and surface translation on mediolateral sway

The control of mediolateral standing balance is altered in many clinical populations, due in part to disrupted sensorimotor processing. Sensory perturbations, as evoked by musculotendon vibration, can provide insight into the contributions of individual sources of sensory feedback to this control. The purpose of this study was to investigate whether hip abductor vibration can elicit mediolateral sway at frequencies <1 Hz, which dominate standing posture. Secondarily, we quantified the effects of mediolateral surface translations in this frequency range. Participants (n=12) without neurological or orthopedic conditions completed a series of standing trials in which we quantified center of pressure motion. In a subset of trials, time-varying hip abductor vibration was delivered, with vibration intensity following sum-of-sine trajectories with frequency content from 0.1-0.9 Hz. In other trials, the standing surface translated mediolaterally following similar trajectories. Participants were not provided instructions regarding how to respond to the stimuli. Vibration significantly increased mediolateral sway for frequencies greater than 0.5 Hz, while surface translation caused substantial sway increases throughout the investigated frequency range. The effects of vibration were observed in the frequency range typically interpreted as reflecting feedback-driven corrective responses, suggesting the potential of this approach to influence balance performance through sensory augmentation.