The Effect of Stroboscopic Vision-Assisted Exercise Training on Ankle Muscle Architecture in Chronic Ankle Instability Rehabilitation

Ankle sprain, particularly injuries to the lateral ligament complex of the ankle joint, is one of the most common lower extremity injuries among athletes [1]. The prevalence of sports-related ankle injuries ranges between 20% and 50%, and according to the American Academy of Orthopaedic Surgeons, approximately 25% of athletic injuries are related to the foot and ankle. High-performance sports such as basketball, football, and volleyball, which involve running, jumping, and sudden directional changes, place significant mechanical load on the ankle, thereby substantially increasing the risk of injury [2].Numerous potential risk factors for the incidence and recurrence of lateral ankle sprains (LAS) have been identified in the literature. These include a history of prior sprains, gender, height, body weight, anatomical foot posture, malalignments such as genu varum and pes cavovarus, joint laxity, range of motion, muscle strength, proprioception, reaction time, and postural sway [5]. muscle strength, reaction time, and postural sway [8].

High rates of re-injury and long-term sequelae following ankle sprains have been documented. Previous studies have shown that at least 73% of individuals who experience recurrent ankle sprains develop residual symptoms such as pain, a sense of giving way, a lack of confidence in the ankle, loss of proprioception, and neuromuscular control deficits.These factors increase the risk of re-injury and the likelihood of developing chronic ankle instability (CAI) [9]. Although the mechanisms behind recurrent sprains are not fully understood, studies indicate decreased muscle activation post-injury, prolonged response times to perturbations, and altered activation onset of the evertor, plantar flexor, and dorsiflexor muscles. The primary clinical goal following a lateral ankle sprain (LAS) is to prevent recurrence [23]. In this regard, conservative treatment is considered the primary approach for symptom management and recurrence prevention. Understanding etiological factors, mechanisms, and triggers underlying recurrent LAS is crucial for designing effective rehabilitation exercises [24]. The ROAST consensus by the International Ankle Consortium underscores the importance of addressing mechanical and sensorimotor deficits following LAS [25].

Reduced somatosensory input at the ankle joint and increased reliance on visual cues are considered key contributors to the sensation of giving way and repeated sprains [26]. Such somatosensory changes can negatively impact joint position and movement sense, becoming critical injury risk factors. Although definitive strategies to modify motor cortex excitability are yet to be developed, interventions targeting these neural components are vital for optimal recovery and the prevention of somatosensory dysfunction [27]. Traditional rehabilitation approaches for recurrent sprains typically include strength, proprioception, and dynamic balance exercises. Balance training has long been a cornerstone of rehabilitation for individuals with chronic ankle instability (CAI), as it is believed to effectively enhance mechanoreceptor activity through stimulation of the ankle capsule and ligaments. This process enhances sensory output and activates gamma motor neurons during training [28,29]. Multimodal comprehensive exercise protocols are regarded as effective treatment options for individuals with CAI [30,31].

Integrating targeted rehabilitation interventions aimed at restoring proprioception, muscle strength, and neuromuscular control is essential for breaking the cycle of sensory and motor dysfunction. Recent studies support that combining proprioceptive and strengthening exercises improves functional stability and reduces recurrence risk [32]. However, earlier studies suggest traditional CAI interventions inadequately address post-sprain somatosensory deficits and fail to modify the increased reliance on visual cues in CAI patients [33,34]. Therefore, treatment strategies targeting neurophysiological dysfunctions may offer a promising approach in CAI rehabilitation. These interventions, focusing on somatosensory deficits, could provide a novel perspective in managing CAI and significantly enhance rehabilitation outcomes [33].

The effects of visual input on somatosensory function have gained attention in recent years. Stroboscopic visual training, involving intermittently disrupted visual feedback using specially designed glasses, is based on this principle [35]. These stroboscopic glasses alternate between transparent and opaque states every 100 milliseconds, reducing visual input and prompting the central nervous system to rely more heavily on somatosensory and vestibular information [36]. Such visual feedback tools offer a novel approach to proprioceptive training, enhancing neuromuscular and postural control [37]. Literature indicates that using these glasses significantly improves postural control in individuals with functional ankle instability following rehabilitation [35]. Stroboscopic glasses incorporated into proprioceptive exercises may help the central nervous system recalibrate proprioceptive input weighting, thereby enhancing the use of somatosensory and vestibular afferents for neuromuscular control [38]. This supports improved postural control and safer responses to perturbations in CAI patients [36].

Lee et al. investigated the effects of stroboscopic visual training on reweighting visual input in individuals with recurrent ankle sprains. The group using stroboscopic glasses showed improved eversion and dorsiflexion angles as well as increased activation in the tibialis anterior and peroneus longus muscles [39]. However, no study to date has explored the effects of these glasses on ankle muscle architecture in individuals with recurrent sprains.

Currently, there is no comprehensive study examining the changes in muscle architecture and performance around the ankle in athletes with recurrent ankle sprains. This underscores the need for in-depth investigation into these changes and their impact on ankle stability. The aim of this study is to investigate the effects of an 8-week combined balance and plyometric exercise program using stroboscopic glasses on muscle morphology, dynamic balance, and proprioception in athletes with a history of ankle sprains. The primary objective is to assess the effectiveness of innovative rehabilitation strategies and their integration into clinical practice. Ultimately, the study seeks to accelerate recovery, reduce recurrence risk, and support long-term functional outcomes. Additionally, the findings are expected to fill current gaps in the literature on muscle architecture and performance, contributing scientifically to rehabilitation protocols.

Inclusion criteria

• At least 5 years of active participation in any sports branch.
• At least two significant LAS incidents associated with inflammatory symptoms (pain, swelling).
• Most recent sprain occurred at least 3 months before study commencement.
• Feeling of ankle giving way at least twice in the past 6 months.
• No history of surgical intervention affecting lower extremity sensorimotor function and no history of ankle fractures.
• Cumberland Ankle Instability Tool (CAIT) score ≤25.
• Foot and Ankle Ability Measure (FAAM) score below 90%.
• FAAM Sports subscale score below 80%.

Exclusion criteria

• History of any ankle fracture.
• Surgical intervention or systemic disease affecting lower extremity sensorimotor function.
• History of neurological disorders.
• Acute musculoskeletal injury to the lower extremity within the last month.
• Visual or vestibular disorders affecting balance or coordination.