A review of concurrent sonified biofeedback in balance and gait training.

Background: Sonified biofeedback is a subtype of auditory biofeedback that conveys biological data through specific non-verbal sounds. It can be designed to provide augmented biomechanical feedback in near-real-time when provided as "concurrent" biofeedback. As a practice that developed spanning across engineering and the arts, sonified biofeedback can extend beyond simple tones and beeps, towards more fully incorporating music in movement training. Sonified biofeedback may leverage the motivational aspects of music in movement training, the neuroplasticity benefits demonstrated from participation in music-based interventions, and neurological auditory-motor coupling, all while providing task-relevant cues to facilitate motor (re)learning. Sonified biofeedback may also provide similar benefits as rhythmic cueing (e.g., rhythmic auditory stimulation), or added benefits because sonified biofeedback does not impose a strict isochronous rhythm when it follows rhythms that are driven by outputs of the motor control system. In this review paper, the unique opportunity presented by concurrent sonified biofeedback as a movement training tool for balance and gait is introduced and discussed.

Results and discussion: This review paper brings together prior research from clinical, engineering, and artistic design sources using sonified biofeedback in balance and gait training across diverse end-users to highlight trends, reveal gaps in knowledge, and provide perspective for future work in the area. The goal was to review progress and critically assess research using sonified biofeedback during movement training for postural control or gait. 49 papers were selected based on their experimental investigation and statistical analyses of the effects of using sonified biofeedback to assist in movement training for feet-in-place balance tasks (20 papers) or gait tasks such as walking and running (29 papers). The sound design choices, experimental design features, and movement training results are summarized and reviewed. All but two studies reported at least one statistically significant positive effect of training with sonified biofeedback in biomechanical, clinical, or psychosocial measures. Conversely, only seven studies shared any negative effect on one biomechanical, clinical, or psychosocial measure (with five of these studies also reporting at least one other positive effect). After describing these encouraging findings, this review closes by sharing perspectives about future directions for designing and using sonified biofeedback in balance and gait training, and opportunities for more cohesive growth in this practice. One such suggestion is to pursue sonified designs and experimental designs that can translate to the neurorehabilitation field. This includes strategically selecting control groups and evaluation tasks to understand if improvements from training with one task transfer to additional relevant movement tasks. Additionally, it is important that future publications share details about the design processes and sound designs so researchers can more readily learn from one another.

Conclusions: Overall, this review shares the positive impact of using sonified biofeedback in balance and gait training. This review highlights the evidence of existing successes and potential for even more impactful future positive effects from using sonified biofeedback to help diverse populations with a spectrum of balance and mobility challenges and goals.