## 2 Materials and Methods  
### Participants  
To ensure the statistical power of the study, the required sample size was determined by employing the G*Power 3.1.9 software, in conjunction with previous research and the statistical methods employed [21]. The power, type I error rate (\(\alpha\)), and effect size were set to 0.95, 0.05, and 0.4, respectively. Calculations revealed that a minimum of 24 individuals was needed; considering the potential for 20% of invalid samples, the minimum sample size was determined to be 29 individuals. Consistent with the selection criteria established by the International Ankle Association [22], 15 individuals diagnosed with unilateral FAI were recruited as the experimental group. Inclusion was determined based on scores from the Cumberland Ankle Instability Tool (CAIT), including the anterior drawer test. The experimental group comprised 8 males and 7 females. This group was categorized by their athletic specialty, consisting of 5 basketball specialists, 4 soccer specialists, 3 volleyball specialists, and 3 badminton specialists. A control group of 15 individuals, matched in terms of gender, morphological characteristics, and athletic background to the FAI group participants, was also established (Table 1). The corresponding unstable side for matching was identified for each control participant. Participants were actively recruited through a combination of university sports team databases, social media postings, and flyers displayed in relevant facilities. Prospective participants were provided with detailed information about the study's objectives, procedures, potential risks, and benefits. They were given ample opportunities to ask questions and were included in the study only after providing written informed consent. This study was conducted in accordance with the guidelines of the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of Soochow University (approval number: SUDA20221005H03).  
Inclusion Criteria for the FAI Group: 1 A history of at least one unilateral ankle sprain, with the initial sprain occurring at least 12 months prior to the trial and presenting with inflammatory symptoms (pain, swelling, etc.) that interrupted physical activity for at least 1 day; 2 no history of severe lower-limb injuries, except for ankle sprains [23]; 3 CAIT score \(\leq\) 24 [24]; 4 FAI present in only one ankle.  
Exclusion Criteria for the FAI Group: 1 History of lower-limb surgery [25]; 2 acute musculoskeletal injury to other joints in the lower limb within the month prior to the formal trial; 3 bilateral FAI [23]; 4 congenital joint deformity; 5 positive anterior drawer test result or tatar tilt; 6 CAIT score > 24; 2 obvious psychological, mental, or cognitive abnormalities with Montreal Cognitive Assessment (MoCA) score < 26 [26].  
Inclusion Criteria for the Control Group: 1 CAIT score \(\geq\) 28 [24]; 2 gender, morphological characteristics, and athletic background matched with the FAI group participants.  
Exclusion Criteria for the Control Group: 1 CAIT score < 28; 2 history of musculoskeletal surgery on the lower limb; 3 acute joint injury within the month prior to the trial; 44 inability to complete assessments as required or missing data during the trial; 5 obvious psychological, mental, or cognitive abnormalities with MoCA score < 26 [26].