## 2 Methods
### Instruments  
Anthropometric measurements: Each participant's anthropometric features (weight, height, leg length) were recorded and BMI was calculated. _CAIT Questionnaire:_ This questionnaire was developed for subjectively assessing functional ankle instability and has been proven to be reliable and valid. The CAIT consists of nine items with multiple choice options, making the tool simple to complete and precise. A discrete score is given for the left and right ankles, with a maximum score of 30. The lower the score, the lower the ankle function A score of \(\leq\)25 on the CAIT questionnaire indicates self-reported ankle instability [15]. Ankle Strain Questionnaire: This questionnaire includes five yes/no questions, examining the participant's ankle injury history. The questions include the following questions: Did your first ankle sprain happened more than a year ago? (yes/no); Did your last ankle sprain happened more than 3 months ago? (yes/no); Did your previous ankle sprain/s prevented you from doing physical activity for at least one day? (yes/no); Did you have an inflammation or swelling around your ankle after the sprain? (yes/no); Did you sprained your ankle at least twice? (yes/no). AII Questionnaire: The third and final questionnaire included nine yes/no questions assessing ankle instability [16]. Positive answers for at least five questions, including a positive answer for the first question, indicated ankle instability. BalanceTutor Treadmill: This apparatus is an innovative perturbation treadmill that enables postural control and balance training. The participant is protected by a harness on a treadmill platform that moves in medial/lateral planes enabling simulation of both slipping and tripping while undertaking standing or walking tasks. The system allows the incorporation of varying degrees of task difficulty level (up to 20 possible levels, depending on the participants' abilities). Sensors that are integrated into the BalanceTutor Treadmill enable a range of controlled perturbations - both expected and unexpected [29]. The participants' reactive postural control was tested in seven different conditions: (1) standing on both legs with their eyes open (SO); (2) standing on both legs with their eyes closed (SC); (3) standing tandem with the dominant leg placed forward (TD); (4) standing tandem with the non-dominant leg placed forward (TND); (5) standing on one leg with perturbation to the lateral side (SLSS), whereby the participants alternate the standing leg at each level; (6) standing on one leg with perturbation to the medial side (SLOS), the participant alternates the standing leg; and (7) walking (3 km/h). The tests are presented in Figure 1A-D.  
All participants started in either condition 1 or 2 (randomized), followed by either condition 3 or 4 (also randomized). Finally, the participants performed conditions 5, 6, and 7. In each condition, perturbations were presented every 12-20 s, with an associated increased acceleration speed and in an unexpected direction (right/left), except for the SLSS and SLOS positions. \"Loss of postural balance\" was defined as the level of perturbation at which the original location of the foot in the standing conditions was altered, stepping beyond the treadmill's lateral borders, any change to hand position (except during walking), or crossing over the legs while walking. The velocity of the platform's movement increased with every perturbation in the SO, SC, TD, TND, and walking positions, and with every second perturbation in the SLSS and SLOS positions. AMEDA Device: This device evaluates ankle proprioception ability by measuring ankle inversion movement discrimination.