## 4 Discussion  
The aim of this study was to investigate the effects of different forefoot medial-lateral height differences on lower limb joint kinematics and kinetics during the stance phase of running. The running shoes used in the experiment had height differences only in the medial-lateral aspect, with all other structural aspects being identical, and the running speed was a self-selected comfortable pace. According to the experimental results, the forefoot height difference significantly affected the biomechanical characteristics of the lower limb joints. Compared to the neutral shoe (NS), different height difference conditions exhibited distinct differences. Of note, the changes in lower limb joint parameters did not linearly increase with increasing height difference values, suggesting a certain biomechanical adaptability of the human body. However, excessive variations might lead to diminished responses or require longer adaptation periods, confirming our initial hypotheses. Particularly, under the L6 condition, significant differences in hip and knee flexion-extension moments during landing and push-off were observed, which align with similar biomechanical changes reported in their study involving altered footwear [27], along with a significant increase in ankle dorsiflexion work and a significant decrease in inversion-eversion work. Under the M9 condition, the hip flexion-extension peak moment, power, and work decreased in the sagittal plane. Additionally, significant differences in ankle dorsiflexion angular velocity were observed under the M6, M9, L6, and L9 conditions, with minimal impact on joint angles. In this experiment, the most pronounced alterations in lower limb joint parameters occurred when subjects wore shoes with varying forefoot height discrepancies, particularly under the L6 condition. These findings suggest adaptive adjustments in the lower limb kinematic chain, possibly driven by shifts in foot contact patterns [28]. The increased forefoot height in the L6 design facilitated initial lateral foot contact during running, which likely influenced foot posture. Throughout the landing and propulsion phases, there was a notable tendency for the foot to adopt a dorsiflexed position, thereby enhancing dorsiflexion range and intensity. This heightening of lateral foot height also altered the distribution of foot loading, potentially augmenting the engagement of lateral structures while alleviating stress on medial structures such as the calcaneus and metataralsals. These biomechanical adaptations may have consequential implications for ankle joint moments across both sagittal and coronal planes. Studies have shown that forefoot shoes significantly increase ankle dorsiflexion moments and Achilles tendon load but effectively reduce the load on the patellofemoral joint during the support phase of running. However, it is not recommended for novices and beginners to wear forefoot shoes [29]. We speculate that the increase in dorsiflexion work may be associated with a decrease in version work. As more of the load is concentrated on the lateral forefoot region, the muscles of the plantar foot may be more involved in dorsiflexion movements, thereby reducing the demand for evasion motion and work. This has important implications for running shoe design and gait adjustment. Selecting appropriate shoe designs and adjusting running posture can reduce the risk of ankle injuries. Research has shown that using lateral wedge insoles can reduce the response time of chronic ankle instability and improve dynamic balance [30]. It is worth noting that in the analysis of results, we found significant differences in peak ankle angular velocity under four different conditions (M6, M9, L6, L9) compared to NS. We believe that the main reason is mechanical adaptation, and the significant differences in peak ankle angular velocity under different conditions may reflect immediate adaptations of the body to changes in shoe design.