浙江体育职业技术学院

This study aimed to investigate the effects of exercise-induced fatigue on the risk of tibial stress fractures by comparing biomechanical parameters during backhand-side smash landings in elite female badminton players before and after fatigue. Thirteen elite female badminton players performed smash-landing trials before and after fatigue. The AnyBody Modeling System was used for inverse dynamics analysis, and finite element analysis was conducted using the AnyFE2Abq plugin to compute tibial stress and strain. After fatigue, the backhand rearcourt jump smash (BRJS) and the backhand lateral jump smash (BLJS) landing movements showed significantly increased peak tibial acceleration (p = 0.003; p = 0.008), vertical average loading rate (p = 0.024; p = 0.040), and vertical instantaneous loading rate (p = 0.007; p = 0.029. Moreover, the simulated tibialis anterior muscle force significantly decreased after fatigue (p = 0.004; p = 0.046). Finite element analysis further revealed markedly increased tibial stress and strain after fatigue, with peak stress and strain reaching multiple times the pre-fatigue values (peak stress: BRJS anterior medial, 224.0%; BRJS posterior, 213.2%; BLJS anterior medial, 348.6%; BLJS posterior, 522.8%; peak strain: BRJS, 241.1%; BLJS, 243.7%). Exercise-induced fatigue increased tibial acceleration and vertical loading rates during smash landings in elite female badminton players. Tibial stress and strain also increased, suggesting a potentially higher risk of tibial stress fracture.

This study aimed to investigate the differential effects of maximal strength training (MST) and maximal power training (MPT) on lower limb explosive power in adolescent beach volleyball athletes (ABVAs), and to provide scientific evidence for sport-specific training. Twenty-two adolescent beach volleyball athletes (age: 17.3 ± 0.9 years, 13 males, 9 females) were randomly allocated to either the MST group (n = 11) or the MPT group (n = 11). The MST group completed traditional barbell strength training (2-4 RM), whereas the MPT group performed MPT using an air resistance device (40-70% 1 RM). Training was scheduled three times weekly for both groups, with each session lasting 90 min. A 2 (group: MST vs MPT) × 2 (time: pre-test vs. post-test) repeated-measures analysis of variance (ANOVA) were used to analyze changes in measured variables, including lower limb maximal power output (LLMPO), rigid surface vertical jump height (RSVJH), sand surface vertical jump height (SSVJH), 10-m sand surface sprint time (10-m SSST), and Isokinetic knee extensor peak torque (KEPT). After 4 weeks of training, the group-by-time interaction was non-significant for LLMPO (p = .411), but significant for RSVJH (p < .001), SSVJH (p < .001) and KEPT (p < .001). The MPT produced large effects on RSVJH (d = 0.74) and SSVJH (d = 0.71), while the MST had a large effect on KEPT (d = 0.82). Both training modalities can enhance lower limb explosive power in ABVAs, yet they target distinct components of explosive power.

This study applies one-dimensional statistical parametric mapping (SPM1d) to analyze the effects of exercise-induced fatigue on lower limb biomechanics during the landing phase of two high-risk backhand smash movements in female badminton players. It aims to reveal fatigue-induced changes in movement patterns and differences between the two actions, providing scientific insights for performance optimization, injury prevention, and training interventions. Thirteen female elite badminton players were recruited. A fatigue protocol based on a badminton-specific speed test was applied, and SPM1d was used to analyze kinematic and kinetic data before and after fatigue. After fatigue, significant increases were observed in hip coronal range of motion (ROM) (P = 0.024), knee valgus angle (P = 0.037), and trunk lateral tilt (P = 0.012), with significant decreases in hip abduction angle (P = 0.024) and trunk forward flexion (P = 0.048). When comparing the backward jump smash (BRJS) to the lateral jump smash (BLJS), significant differences were found in ankle (sagittal P = 0.006, horizontal P = 0.006) and hip (sagittal P < 0.001, horizontal P < 0.001) ROM, ankle external rotation angle (P = 0.047), knee flexion angle (P = 0.049), hip abduction angle (P = 0.002), trunk forward flexion angle (P = 0.042), ankle inversion torque (P = 0.048), internal rotation torque (P < 0.001), knee inversion torque (P = 0.003), external rotation torque (P = 0.019), hip adduction torque (P = 0.003), and forward ground reaction force (GRF) (P = 0.05), all of which were significantly greater in BRJS. However, BRJS showed significantly smaller hip flexion angle (P = 0.014), hip extension torque (P = 0.019), hip internal rotation torque (P = 0.046), knee extension torque (P = 0.024), trunk lateral tilt (P = 0.004), lateral GRF (P < 0.001), and vertical GRF (P = 0.003) compared to BLJS (1) The increase in knee valgus angle, trunk flexion angle, and lateral tilt angle, as well as the decrease in hip abduction angle caused by exercise-induced fatigue, increases the risk of ACL injuries in the lower limbs. (2) Both high-risk smash landings pose injury risks. In BRJS, increased ankle inversion/internal rotation torques heighten ankle sprain risk, while higher forward GRF and knee valgus torque raise ACL injury risk. In BLJS, greater medial GRF increases ankle sprain risk, whereas higher knee extension torque, trunk lateral tilt, and reduced knee/trunk flexion elevate ACL injury risk.

BackgroundBreaststroke is technically complex and requires high neuromuscular coordination. Because muscle synergies describe how multiple muscles are organized into low-dimensional activation modules, they provide a functional read-out of neuromuscular control development during adolescence. This study investigated neuromechanical characteristics of adolescent breaststroke swimmers across performance levels.MethodsTwenty-six male adolescent breaststroke swimmers were divided into elite (n = 13) and amateur (n = 13) groups. During five 25-m maximal breaststroke trials, two-dimensional underwater video and synchronized surface EMG from 16 muscles were collected. Main outcomes included discrete joint angles, the minimum number of synergies, variance accounted for (VAF), spatial weightings, and temporal activation coefficients. Group differences were assessed using independent-samples or Mann-Whitney U tests, FDR-adjusted spatial-weighting comparisons, SPM1D for activation curves, and Cohen’s d effect sizes.ResultsAt v2, the elite group showed greater hip flexion (43.78° ± 6.92° vs. 34.39° ± 11.32°, P = 0.018, d = 1.00), smaller knee flexion (122.93° ± 8.77° vs. 128.93° ± 4.84°, P = 0.041, d = −0.85), and smaller hip abduction (36.28° ± 7.19° vs. 45.22° ± 7.87°, P = 0.006, d = −1.19). VAF was similar between groups (91.27% ± 0.69% vs. 91.20% ± 0.73%, P = 0.583, d = 0.10), whereas the elite group required fewer minimum synergies (5.42 ± 0.72 vs. 6.03 ± 0.66, P < 0.001, d = −0.88). FDR-adjusted spatial-weighting and SPM1D analyses indicated that SYN2 and SYN4 were the main modules distinguishing the groups, with temporal differences concentrated from late glide to in-sweep.ConclusionPerformance-related differences mainly reflected lower-limb posture during glide and synergy control during propulsion-related phases. Fewer minimum synergies under comparable VAF conditions suggest greater synergy integration in high-level swimmers. These findings link adolescent breaststroke performance to task-specific multi-muscle coordination.

Manual kinematic analysis in swimming is labor-intensive and often lacks the immediacy required for elite training. This study presents an automated vision-language framework to deliver real-time kinematic profiling and coaching diagnostics. A robust object detection pipeline using YOLOv11 was developed, incorporating a splash-injection strategy to handle aquatic occlusion. Kinematic metrics (velocity, distance) were extracted via homography transformation. To automate pedagogical feedback, the DeepSeek-V3 Large Language Model was integrated to interpret these metrics and generate structured coaching reports. The proposed method achieved a mean Average Precision (mAP@0.5) of 94.64