The goal of this randomized clinical controlled trial is examine the effects of gait training with auditory biofeedback (AudFB) on gait biomechanics, clinical measures of ankle joint health, and patient-centered outcomes. The following specific aims will achieve this objective:

• Specific Aim 1: Determine if a 6-week gait training with AudFB intervention improves lower extremity biomechanics compared to a Control condition in participants with CAI.
• Specific Aim 2: Determine if a 6-week gait training with AudFB reduces talar cartilage deformation compared to a Control condition in participants with CAI.
• Specific Aim 3: Determine if a 6-week gait training with AudFB reduces episodes of ankle giving-way and reduces self-perceived severity of symptoms relative to a Control condition in participants with CAI.

Participants will:

• Complete 12 intervention sessions over a 6-week period of walking, ruck marching, and runninig.
• Complete testing sessions before and after the intervention, then after 6 and 12-months following the intervention.

Background: Ankle injuries account for the highest musculoskeletal injuries among conventional and special warfare combatants. In the civilian population, 40% of lateral ankle sprain patients will develop chronic ankle instability (CAI). If the same frequency is true in military settings, then up to 36,800 service members develop CAI annually. CAI contributes to the total number of medically non-available service members, creates a substantial economic burden, impacts the quality of duty-relevant task performance, and generates a large population of service members who require long-term care after retirement. There are no evidence-based gait training interventions for patients with CAI despite abnormal biomechanical patterns leading to recurring injuries linked to ankle osteoarthritis (OA) development. Overall, the current rehabilitation strategies are insufficient for preventing complications following an ankle sprain.

Hypothesis/Objectives: The overall objective of this study is to examine the effects of gait training with auditory feedback (AudFB) on gait biomechanics, ankle joint health, and patient-centered outcomes. Our central hypothesis is that a 6-week (12 sessions) gait training program with AudFB will lead to short and long-term improvements in walking, rucking, and running biomechanics, talar cartilage deformation patterns, giving way episodes and severity of symptoms.

Specific Aims:

Aim 1: Determine if a 6-week gait training with AudFB improves lower extremity biomechanics compared to a Control condition in participants with CAI.

Aim 2: Determine if a 6-week gait training with AudFB reduces talar cartilage deformation compared to a Control condition in participants with CAI.

Aim 3: Determine if a 6-week gait training with AudFB reduces ankle giving-way episodes and severity of CAI symptoms relative to a Control condition in participants with CAI.

Study Design: Specific Aims 1-3 will be addressed using a single-blinded, multi-site randomized controlled trial design with data collected at the University of Kentucky (UK) and University of North Carolina at Charlotte (UNC Charlotte) (Figure 3). Patients with CAI will be randomized to the AudFB or Control group at a 1:1 allocation ratio (n=100; 50 UK and 50 UNC Charlotte). Participants will report to the UK Sports Medicine Research Institute or the UNC Charlotte Biodynamics Research Laboratory to complete outcomes for Specific Aims 1-3 at Baseline, Post-Intervention, and 6- and 12-Month Post-Intervention sessions, which will record: 1) lower extremity biomechanics during walking, rucking, and running, 2) talar articular cartilage deformation via ultrasonography, and 3) ankle giving way and patient-reported outcomes of CAI symptom severity. The AudFB group and Control group will complete 12 sessions of supervised gait training over 6 weeks and follow the same condition-based progression design. Each session will last roughly 25 minutes and begin with 10 minutes of walking followed by 15 minutes of the designated condition for that session (walking, rucking, or running). The AudFB group will receive real-time biofeedback derived from plantar forces of the lateral foot. The control group will be instructed to walk comfortably. Both groups will wear standard neutral athletic shoes and wireless in-shoe force insoles during every intervention session for standardization of testing procedures.

Impact and Military Benefit: The Investigators expect participants with CAI in the AudFB group will exhibit improvements in patient-centered outcomes and subsequent clinician-centered outcomes regarding biomechanics and ankle joint health. These findings will signal that our novel AudFB gait training protocol is critical to short- and long-term quality of life in patients with CAI. This study will provide a short-term impact by providing clinicians with an easily accessible and feasible tool to implement gait training to optimize return to duty in service members with CAI history. The long-term impact of this study will be related to the expansion of the rehabilitation paradigm by providing an evidence-based gait training protocol that has the potential to mitigate the early onset of ankle OA.

Inclusion Criteria:

• Physically active adults (defined as participants reporting a score of =4 on the National Aeronautics and Space Administration (NASA) Activity Instrument and indicating they can run for at least 20 consecutive minutes)
• History of ankle sprain
• 2 episodes of "giving way" in the past 6-months
• must answer "yes" to =5 questions on the Ankle Instability Instrument (AII) and =11 on the Identification of Functional Ankle Instability (IdFAI)

Exclusion Criteria:

• an ankle sprain in the previous four weeks or lower extremity neuromusculoskeletal injury other than to the ankle in the last 12 months
• history of surgery in the lower extremity
• fracture to the lower extremity in the past 12 months or a fracture that required open-reduction internal fixation
• history of neurological disease, vestibular or visual disturbance or any other pathology that would impair sensorimotor performance or gait
• current participation in a formal ankle joint rehabilitation program
• a concussion in the last 12 months
• report a cardiovascular, metabolic, or renal disease, or signs and symptoms that suggest such condition or have been told by a medical provider not to engage in vigorous physical activity (such as running).