## 4 Discussion
### Impact of Different Footwear Conditions on the Biomechanical Adaptability of Individuals with FAI  
The results of this study reveal significant biomechanical changes in individuals with FAI under different footwear conditions, reflecting their adaptive adjustments to varying support conditions. Compared to the barefoot group, the FAI group showed a reduced ankle-joint plantarflexion angle when landing under the shoe-wearing condition, indicating that with additional support, FAI patients can better control ankle motion, minimize excessive joint activity, and thereby enhance movement stability and reduce the risk of injury [32, 33], which aligns with Hypothesis 2 of this study. Concurrently, the biomechanical characteristics of FAI patients under the shoe-wearing condition further suggest that by increasing the encapsulation and stability of the foot, they may optimize their adaptability to better meet the challenges of movement. The research by [PERSON] et al. [34] also supports the significant effect of wearing shoes in enhancing ankle joint function during movement, demonstrating a clear advantage of wearing shoes in this regard. Moreover, the similar ankle joint angles observed between individuals with FAI and healthy individuals during single-leg drop landing movements under barefoot conditions suggest that, due to their poorer postural stability and proprioception [35], barefoot conditions may better activate and utilize their inherent foot functions, thus promoting a movement pattern closer to that of healthy individuals. This is consistent with the findings of [PERSON] et al. [13], which show that barefoot exercise significantly adjusts lower-limb biomechanical functions, not only promoting the development of small muscle groups in the foot, increasing their cross-sectional area, but also potentially providing additional foot stability and sock absorption. This could be extremely beneficial for the rehabilitation of individuals with FAI, as barefoot training may help them enhance foot proprioception, balance, and posture control. Furthermore, for the special group of individuals with FAI, wearing shoes may provide better support and protection for the ankle joint, which is crucial for improving movement stability and reducing the risk of injury [17]. However, this additional physical support may also affect foot proprioception, as wearing shoes might limit direct sensory feedback from the foot to the ground, affecting the individual's perception of ground conditions. Meanwhile, barefoot exercise may help improve foot proprioception and muscle strength [36], bringing the foot function of individuals with FAI closer to that of healthy individuals in certain aspects. The biomechanical characteristics in barefoot conditions may assist individuals with FAI in perceiving and controlling foot movements better during the rehabilitation process, thereby promoting a more natural movement pattern. However, barefoot exercise may also deprive individuals with FAI of the physical protection offered by shoes, increasing the risk of ankle injury, especially when the ankle joint is already compromised. Research by [PERSON] et al. [37] indirectly supports this viewpoint, suggesting that the choice of footwear conditions should be determined based on the individual's specific needs. Moreover, according to the results of this study, the larger knee flexion angle and shorter T_vGRF observed in individuals with FAI compared to healthy individuals during single-leg drop landing movements persist, indicating that individuals with FAI may adopt specific landing strategies under the footwear conditions employed in this study. Therefore, for individuals with FAI, the choice between wearing shoes or being barefoot should be based on their individual circumstances and rehabilitation goals, as well as their adaptability and stability under different movement conditions.