Introduction: Chronic Ankle Instability (CAI) is a musculoskeletal condition that evolves from acute ankle sprains, and its underlying mechanisms have yet to reach a consensus. Mounting evidence suggests that neuroplastic changes in the brain following ankle injuries play a pivotal role in the development of CAI. Balance deficits are a significant risk factor associated with CAI, yet there is a scarcity of evidence regarding the sensorimotor cortical plasticity related to balance control in affected individuals. This study aims to evaluate the differences in cortical activity and balance abilities between patients with CAI and uninjured individuals during a single-leg stance, as well as the correlation between these factors, in order to elucidate the neurophysiological alterations in balance control among patients with CAI.Methods: The study enrolled 24 patients with CAI and 24 uninjured participants. During single-leg stance, cortical activity was measured using a functional near-infrared spectroscopy (fNIRS) system, which included assessments of the pre-motor cortex (PMC), supplementary motor area (SMA), primary motor cortex (M1), and primary somatosensory cortex (S1). Concurrently, balance parameters were tested utilizing a three-dimensional force platform.Results: Independent sample t-tests revealed that, compared with the uninjured individuals, the patients with CAI exhibited a significant increase in the changes of oxyhemoglobin concentration (ΔHbO) during single-leg stance within the left S1 at Channel 5 (t = 2.101, p = 0.041, Cohen’s d = 0.607), left M1 at Channel 6 (t = 2.363, p = 0.022, Cohen’s d = 0.682), right M1 at Channel 15 (t = 2.273, p = 0.029, Cohen’s d = 0.656), and right PMC/SMA at Channel 11 (t = 2.467, p = 0.018, Cohen’s d = 0.712). Additionally, the center of pressure root mean square (COP-RMS) in the mediolateral (ML) direction was significantly greater (t = 2.630, p = 0.012, Cohen’s d = 0.759) in the patients with CAI. Furthermore, a moderate positive correlation was found between ML direction COP-RMS and ΔHbO2 in the M1 (r = 0.436; p = 0.033) and PMC/SMA (r = 0.488, p = 0.016), as well as between anteroposterior (AP) direction COP-RMS and ΔHbO in the M1 (r = 0.483, p = 0.017).Conclusion: Patients with CAI demonstrate increased cortical activation in the bilateral M1, ipsilateral PMC/SMA, and contralateral S1. This suggests that patients with CAI may require additional brain resources to maintain balance during single-leg stance, representing a compensatory mechanism to uphold task performance amidst diminished lateral balance ability in the ankle joint.

Long short-term memory (LSTM) networks are widely used in biomechanical data analysis but have the significant limitations in interpretability and decision transparency. Combining graph neural networks (GNN) with gate recurrent units (GRU) may offer a better solution. This study proposes and validates a hybrid GNN-GRU model for predicting baseball pitching speed and enhancing its interpretability using layer-wise relevance propagation (LRP). C3D data from 53 baseball athletes were downloaded from a public dataset. Kinematic features of 9 joints and pitching speed during the pitching process were calculated using Visual3D, resulting in a total of 208 valid pitches. The feature data were input into both LSTM and GNN-GRU hybrid models, with hyperparameters tuned using particle swarm optimization. LRP was employed to obtain the contribution rate changes of kinematic features to the prediction results throughout the pitching cycle. The prediction accuracy of the models was evaluated using mean absolute error (MAE), mean squared error (MSE), and R-squared (R²). The results showed that there were the significant statistical differences in the MAE and R² metrics between the LSTM model and the GNN-GRU model in predicting pitching speed on the test set. The MAE (P = 0.000, Z = − 5.170, Cohen’s d = 1.514) and R² (P = 0.000, Z = − 2.981, Cohen’s d = 2.314) of the LSTM model were significantly lower than those of the GNN-GRU model. Compared to LSTM, the GNN-GRU model achieved better prediction accuracy but was potentially more susceptible to the influence of data variability. Moreover, the GNN-GRU-based model demonstrated the better interpretability and decision transparency.

The effectiveness of plyometric training in adolescent basketball players has not been fully elaborated, especially its effect on enhancing change of direction abilities. Thirty male adolescent basketball players were divided into plyometric and resistance training groups for an 8-week training period. The improvement in change of direction abilities before and after the training was assessed using the Lane Agility Drill test. Motion capture system, force platforms, and electromyography were utilized to investigate the characteristics of lower limb kinematic and kinetic features before and after training. At post-test, the Lane Agility Drill finish time for the plyometric group was significantly less than that of the resistance training group ( P < 0.05, Cohen's d = 0.551), and the post-test Lane Agility Drill finish time for the plyometric group was significantly less than their pre-test time ( P < 0.05, Cohen's d = 0.746). At post-test, the plyometric training group showed greater increases in peak impulse ( P < 0.05, Cohen's d = 0.464), peak power ( P < 0.05, Cohen's d = 0.684) compared to resistance training group. The study's conclusion indicates that compared to resistance training, plyometric training more significantly enhances athletes’ change of direction abilities. This improvement is attributed to the superior transfer of strength and explosive power gains acquired during training. Additionally, plyometric training optimizes energy utilization and production during jumping and running.

This study aimed to investigate the impact of different foot support patterns on knee joint loading in elite table tennis athletes. Eighteen right-handed with shake-hand grip, national I level table tennis athletes were included. Their average age was 20.33 ± 1.53 years, with a height of 1.73 ± 0.08 meters, weight of 66.75 ± 9.35 kilograms, and 11.67 ± 1.81 years of training experience. The athletes performed forehand loop strokes using different support patterns: alternating support pattern (ASP) and full-foot support pattern (FSP). Kinematic and kinetic data were collected using 8 infrared cameras and 3 force plates. Compared to the ASP, the FSP significantly reduced heel-to-forefoot rotation angle (−30.67%), knee compressive force (−9.14%), knee extension moments (−13.94%), hip (−5.6%) and thorax (−3.8%) Z-axis angular speed, but increased free moment by 19.92%. The moment graph also revealed the FSP had a higher knee internal rotation moment (0%∼69%) and external rotation moment (70%∼100%), as well as a higher hip external rotation moment (6%∼64%). The FSP decreased athletic performance and increased knee joint load during the forehand loop. It is recommended that athletes avoid using the FSP during training or competition.

Baseball hitting involves multiple biomechanical variables, and understanding their impact on bat energy is crucial for improving performance. However, no studies have explored how biomechanical features affect hitting performance from the perspective of bat energy. This study aimed to systematically investigate the influence of lower limb biomechanical variables on bat energy using factor analysis and stepwise regression methods. Sixteen right-handed baseball players participated in the study. Bilateral lower limb kinematic and kinetic features were calculated and exported using a motion capture system and force platform. Six key factors (F1–F6) were extracted from the 28 biomechanical features. Factors F1 and F5 are correlated with the rotation of the trailing and leading limbs, respectively; F2 correlates with energy production of the leading limb; F3 correlates with linear momentum production; F4 correlates with body posture control; and F6 correlates with body linear movement in the anterior direction. To enhance bat energy, hitters should step towards the incoming ball more rapidly to increase ground reaction force on the leading limb. They should also maximize extension and external rotation of both the leading and trailing limbs, stabilize the trailing limb during body rotation, and ensure proper weight distribution between the leading and trailing limbs.