Objective: To investigate sex differences in lower limb biomechanics during single-leg drop landing in individuals with unilateral Functional Ankle Instability (FAI).Methods: Twenty individuals with unilateral FAI (10 males/10 females) performed single-leg drop landings on unstable and stable limbs respectively. Kinematic data were captured using a Vicon motion capture system, and kinetic data were collected using force plates. Data were analyzed using a 2 × 2 (Sex × Side) mixed-design ANOVA.Results: Significant main effects of Sex were observed for hip flexion and abduction angles at both IC and peak vGRF, with females showing greater hip flexion (p = 0.005; p = 0.023) and smaller hip abduction (p = 0.026; p = 0.003) than males. A significant main effect of Sex was also found for ankle inversion at IC, with females exhibiting greater inversion than males (p = 0.005). For ankle plantarflexion at IC, a significant Sex × Side interaction was detected (p = 0.020); simple effects analysis revealed that females had reduced plantarflexion on the unstable side compared to their stable side (p = 0.010). For peak vGRF, a significant Sex × Side interaction was observed (p = 0.013); post hoc tests indicated that females had higher peak vGRF on the unstable side than males (p = 0.008) and their own stable side (p < 0.001). No significant differences were observed for knee joint angles, T_vGRF, LR, ΔL, or K_leg (p > 0.05).Conclusion: Female individuals with FAI employ a hip-dominant compensatory strategy (increased flexion/reduced abduction) and exhibit greater ankle inversion than males. On the unstable side, they demonstrate reduced plantarflexion compared to their stable side. Males with FAI primarily adopt a joint stiffening strategy with restricted motion. Future research on FAI should incorporate sex differentiation in biomechanical assessments to develop targeted rehabilitation.

Objective: This study examined the effect of three levels of longitudinal bending stiffness (LBS) in carbon-plated shoes on lower limb biomechanics.Methods: Fifteen elite male marathon runners, each with a personal best under 3 h, participated in the study. They were tested wearing shoes with three LBS levels: low (LLBS, 0.31 Nm/deg), medium (MLBS, 0.40 Nm/deg), and high (HLBS, 0.48 Nm/deg). All participants ran at a constant speed of 4.76 m/s. Kinematic and kinetic data were synchronously collected using the VICON motion capture system and three AMTI force plates. Angular parameters of the ankle, knee, hip, and metatarsophalangeal (MTP) joints were calculated using the sagittal plane coordinate system. Joint moments and joint work (positive and negative) at each lower limb joint were analyzed using the built-in inverse dynamics module in Visual3D.Results: In terms of kinematics, the maximum dorsiflexion angle of the MTP joint during the late stance phase and the range of motion during the stance phase was significantly lower in the MLBS to HLBS shoes than in the LLBS shoes. Negative work at the MTP joints was significantly higher in the LLBS shoes than in the HLBS shoes (LLBS: 0.21 ± 0.05 J/kg, MLBS: 0.16 ± 0.03 J/kg, HLBS: 0.13 ± 0.05 J/kg, F = 12.053, p = 0.001). Additionally, the maximum hip extension moment was also significantly affected by LBS (F = 6.561, p = 0.012, η2 = 0.286), with the MLBS (1.49 ± 0.27 Nm/kg) shoes showing lower values than both LLBS (1.80 ± 0.33 Nm/kg, p = 0.021) and HLBS (1.58 ± 0.32 Nm/kg, p = 0.047). The MLBS shoes significantly increased positive work at the ankle joint (LLBS: 0.66 ± 0.08 J/kg, MLBS: 0.71 ± 0.10 J/kg, HLBS: 0.69 ± 0.08 J/kg, F = 3.292, p = 0.047).Conclusions: This study demonstrates that increasing the LBS shoes alters the lower limb biomechanical performance of elite marathon runners. Both MLBS and HLBS conditions reduced MTP joint dorsiflexion, but MLBS shoes significantly increased positive work at the ankle joint and improved joint function while maintaining lower hip joint moments. Among the three conditions, MLBS better balanced mechanical efficiency and natural joint function, suggesting it may be a more biomechanically suitable option for elite marathon runners. These findings provide valuable insights for optimizing LBS in performance shoe design, with MLBS offering a potential advantage in both biomechanical performance and injury prevention.

Objective: To investigate the sex-differentiated effects of Mental Fatigue (MF) on lower extremity biomechanical characteristics during single-leg drop landing among sport science university students. Methods: Twenty-eight healthy sport science university students (14 females, 14 males) performed single-leg drop landings from a 30 cm height before and after MF induction via a 45-min Stroop task. Kinematic and kinetic data during landing were synchronously captured using a Vicon infrared motion capture system and Kistler force plates. A 2 × 2 mixed-design analysis of variance (ANOVA) was employed. Results: At Initial Contact (IC), males exhibited significantly smaller ankle plantarflexion angles post-MF compared to baseline ( p < 0.001), and also significantly smaller than females post-MF ( p = 0.005). Post-MF, females exhibited significantly smaller knee flexion angles than males ( p = 0.004). For ankle inversion angle, only a significant main effect of sex was observed ( p = 0.004). No significant differences were found for hip angles or kinetic variables at peak vGRF. Conclusion: At IC, males compensated by reducing ankle plantarflexion, while females compensated by reducing knee flexion, indicating that MF induces a sex-specific strategic reorganization of distal-proximal joint control. These differences disappeared during the peak loading phase, suggesting that MF primarily affects early anticipatory mechanisms rather than the entire impact absorption process. Ankle inversion angle showed only a sex main effect, and hip strategy remained unchanged, further highlighting a hierarchical control logic prioritizing “ankle-knee first, hip later.” This study not only validates the existence of an MF × sex interaction effect but also underscores the theoretical value of non-significant indicators under the null hypothesis.

Sex differences in the effects of mental fatigue on single-leg drop landing biomechanics among sport science university students.

This study analyzes sit-ski alpine skiing trajectories during gate-turning phases using an inverted pendulum model combined with an advanced kinematic testing system involving inertial sensors and drone video analysis. Data were collected from 11 elite sit-ski athletes during runs on a designated slope segment. The inertial sensor system showed static accuracy of 2° and an average deviation of 0.008 m, while drone video analysis had a mean relative error of 1.36% ± 0.94%. Analysis of 33 gate turns revealed a mean skiing distance of 13.61 ± 2.87 m and mean time of 0.88 ± 0.19 s, with significant positive correlation ( $$\:p$$ < 0.05) between single-gate skiing time ( $${\it\text{t}}_{\text{s}}$$ ) and the minimum distance ( $${\it\text{d}}_{\text{m}\text{i}\text{n}}$$ ) ( $$\:\rho\:$$ = 0.74, $$\:p$$ < 0.01) and lateral distance ( $${\it\text{d}}_{\text{l}\text{e}\text{v}}$$ ) ( $$\:\rho\:$$ = 0.73, $$\:p$$ = 0.01). Simulation with the inverted pendulum model yielded a COM trajectory length of 97.93 ± 2.31 m, 1.66 ± 3.61 m shorter than actual values ( $$\:p$$ = 0.16), and a simulated time of 6.36 ± 0.64 s, showing strong consistency (ICC = 0.85 for time, ICC = 0.45 for trajectory length). These results confirm that optimizing the balance of turning radius, speed, and distance reduces skiing time, supporting the model’s effectiveness in individualizing trajectory optimization for sit-ski alpine skiing.