This interventional study will investigate the effects of stroboscopic visual conditions on gait patterns and lower limb muscle activation in adults with chronic ankle instability (CAI). CAI often results in impaired sensorimotor control, leading to altered gait strategies such as slower walking speed, shorter step length, and increased visual reliance. Stroboscopic glasses intermittently restrict visual input, potentially reducing visual dependence and enhancing proprioceptive feedback.

Participants will complete walking trials under three randomized visual conditions: high-frequency stroboscopic, low-frequency stroboscopic, and no-glasses control. Gait parameters will be measured using the GAITRite system, and surface electromyography (sEMG) will record activation of the tibialis anterior, peroneus longus, and gastrocnemius muscles. Findings may provide insight into sensorimotor adaptation mechanisms and inform rehabilitation strategies to improve functional stability in individuals with CAI.

Chronic ankle instability (CAI) is a frequent outcome after ankle sprains, characterized by recurrent giving-way episodes, pain, and functional limitations. Approximately 40% of individuals with ankle sprains develop CAI, which is associated with deficits in proprioception, neuromuscular coordination, and postural stability. Increased visual reliance is a common compensatory strategy, but this can impair balance and gait when visual input is limited, raising the risk of re-injury.

Stroboscopic glasses alternate between transparent and opaque states, intermittently restricting visual information. This challenges the sensorimotor system, potentially reducing visual dependence and enhancing proprioceptive engagement. Prior research has shown benefits for static and dynamic balance, but little is known about effects on walking in CAI populations.

This randomized crossover study will assess the impact of high-frequency and low-frequency stroboscopic visual conditions compared with normal vision on gait and lower limb muscle activation in CAI. Adults aged 18-45 years with CAIT scores < 24 and a history of ankle instability within 6 months will be recruited. Exclusion criteria include recent lower limb surgery/fracture, systemic conditions affecting balance, or inability to follow instructions.

Participants will perform walking trials on a 5-meter GAITRite walkway under three randomized visual conditions:

1. High-frequency stroboscopic (rapid alternation)
2. Low-frequency stroboscopic (slower alternation)
3. No-glasses control (normal vision)

Gait parameters (step length, step time, gait velocity, swing/stance phases) will be measured, and sEMG (Noraxon) will assess activation of the tibialis anterior, peroneus longus, and gastrocnemius, normalized to MVIC. Subjective measures include CAIT, FAAM, IdFAI, and VAS pain scores.

It is hypothesized that stroboscopic conditions will produce measurable changes in gait and muscle activity compared with control, reflecting adaptive sensorimotor strategies that can inform rehabilitation programs to improve stability, mobility, and reduce re-injury risk.

Inclusion Criteria:

• Individuals with a Cumberland Ankle Instability Tool (CAIT) score of less than 24
• Individuals diagnosed with ankle sprain or instability within the past 6 months

Exclusion Criteria:

• Individuals who have undergone lower limb surgery or experienced a fracture due to ankle trauma within the past 6 months
• Individuals with systemic diseases, such as cardiovascular disorders, that may affect balance
• Individuals who have difficulty understanding or following instructions during assessment or training