Walking With Ears: Altered Auditory Feedback Impacts Gait Step Length in Older Adults

Abstract

Auditory feedback may provide the nervous system with valuable temporal (e. g., footstep sounds) and spatial (e.g., external reference sounds) information that can assist in the control of upright walking. As such, hearing loss may directly contribute to declines in mobility among older adults. Our purpose was to examine the impact of auditory feedback on the control of walking in older adults. Twenty older adults (65-86 years) with no diagnosed hearing loss walked on a treadmill for three sound conditions: Baseline, Ear Plugs, and White Noise. We hypothesized that in response to reduced temporal auditory feedback during the Ear Plugs and White Noise conditions, participants would adapt shorter and faster steps that are traditionally believed to increase mechanical stability. This hypothesis was not supported. Interestingly, we observed increases in step length (p = 0.047) and step time (p = 0.026) during the Ear Plugs condition vs. Baseline. Taking longer steps during the Ear Plugs condition may have increased ground reaction forces, thus allowing participants to sense footsteps via an occlusion effect. As a follow-up, we performed a Pearson's correlation relating the step length increase during the Ear Plugs condition to participants' scores on a clinical walking balance test, the Functional Gait Assessment. We found a moderate negative relationship (rho = -0.44, p = 0.055), indicating that participants with worse balance made the greatest increases in step length during the Ear Plugs condition. This trend suggests that participants may have actively sought auditory feedback with longer steps, sacrificing a more mechanically stable stepping pattern. We also hypothesized that reduced spatial localization feedback during the Ear Plugs and White Noise conditions would decrease control of center of mass (COM) dynamics, resulting in an increase in lateral COM excursion, lateral margin of stability, and maximum Lyapunov exponent. However, we found no main effects of auditory feedback on these metrics (p = 0.580, p = 0.896, and p = 0.056, respectively). Overall, these results suggest that during a steady-state walking task, healthy older adults can maintain walking control without auditory feedback. However, increases in step length observed during the Ear Plugs condition suggest that temporal auditory cues provide locomotor feedback that becomes increasingly valuable as balance deteriorates with age.

Keywords: balance; gait; hearing; locomotion; sound.

Figure 1

Auditory feedback during walking can provide sensory cues that aid in the control of walking balance. (A) Temporal cues such as footsteps provide information about the timing of importance events occurring within the gait cycle. (B) External sounds can provide spatial references about an individual's position and velocity.

Figure 2

Variability of Step time and Step Length. Box plot data for all participants showing the changes in (A) step time variability and (B) step length variability between auditory feedback and arm swing conditions. We found no significant differences in variability for either variable between conditions.

Figure 3

Mean Step time and Step Length. Box plot data for all participants showing the changes in (A) mean step time and (B) mean step length between auditory feedback and arm swing conditions. We found individuals took significantly slower and longer steps during the Ear Plugs condition than during Baseline. * indicates a significant main effect (p < 0.05) between auditory feedback conditions. ♢ indicates a significant simple effect (p < 0.05) between auditory feedback conditions during Arms Free walking trials.

Figure 4

Change in Step Length vs. FGA score. Pearson's correlation showing individual changes in step length observed between the Baseline and Ear Plugs condition and walking balance as assessed by the Functional Gait Assessment score. We found a moderate negative relationship that approached significance (rho = -0.44; p = 0.055), indicating that individuals with the poorest balance increased step length the most during the Ear Plugs condition.

Figure 5

Lateral Center of Mass Dynamics. Box plot data for all participants showing the changes in (A) Peak lateral COM speed, (B) lateral COM excursion, (C) minimum lateral margin of stability, (D) λs, and (E) step width between auditory feedback and arm swing conditions. We found no significant main effects of auditory feedback on control of lateral COM dynamics. * indicates a significant main effect (p < 0.05) between arm swing conditions. ♢ indicates a significant simple effect (p < 0.05) between auditory feedback conditions during the Arms Crossed walking trials.