This study investigated the effects of knee braces with differing stiffness on in vivo knee kinematics and neuromuscular control during single-leg lateral landings. 14 healthy males performed landings under three conditions: no brace (Control), low-stiffness (Type-1), and high-stiffness (Type-2). Kinematics were quantified via dual fluoroscopic imaging, and sEMG recorded seven lower-limb muscles. Brace mechanics were assessed via three-point bending. Statistical analysis used repeated-measures ANOVA (α = 0.05). Kinematically, neither brace restricted knee flexion. Both significantly reduced varus angle (Type-1: 27–100% stance, p = 0.043; Type-2: 60–100% stance, p = 0.033), and Type-2 also lowered peak sagittal flexion acceleration (5.0 rad/s², p = 0.013). Neuromuscularly, Type-1 enhanced multiplanar control, advancing rectus femoris (154.7 ms vs. Type-2, p = 0.005) and vastus lateralis (35.6 ms vs. Control, p = 0.046) activation without increasing rotational instability. Conversely, Type-2 demonstrated a trade-off: despite earlier vastus medialis activation (43.6 ms vs. Control, p = 0.011), it significantly delayed gluteus medius activation (23.9 ms vs. Type-1, p = 0.037) and, critically, exacerbated compensatory internal-rotation acceleration (3.3 rad/s² vs. Type-1, p = 0.006) at peak flexion. The low-stiffness brace leveraged neuromuscular coordination for multiplanar stability, whereas the high-stiffness brace improved frontal-plane protection at the cost of rotational instability. These findings provide biomechanical evidence for the synergistic optimization of mechanical support and neuromuscular adaptation in knee brace design for populations with similar characteristics to the young male athletes studied herein.

The swimming start, which involves interactions with both water and air, has predominantly been studied primarily in terms of spatio-temporal parameters, while its motor control aspects have received limited attention. This study aims to investigate and compare the coordination patterns between the arm and trunk, as well as the thigh and trunk, in S9, S10, and S12 Paralympic swimmers using the continuous relative phase. The study included twenty-one Paralympic swimmers, and the results showed significant differences (p < 0.05) from spm1d (ANOVA) in both arm-trunk and thigh-trunk CRP among the three classes of swimmers. Significant differences were observed in the arm-trunk CRP during the initial (0–8% of time) and end (30–41% of time) parts of the block phase. Both of these two differences are from the comparison of S10 and S12. The thigh-trunk CRP also showed significant differences at the end of the block phase (35–41% of time) and during the flight phase before entry (58–61% of time). Significant differences were observed in post hoc tests between S9 and S10 and between S12 and S10 for the first significant difference. The second significant difference was found between S12 and S10. The results indicate that Paralympic swimmers classified as S9, S10, and S12 tend to exhibit distinct inter-segmental coordination patterns during the dive start. By recognizing different patterns of motor coordination, coaches and trainers can develop individualized training methods to optimize the start performance for swimmers with different impairments (different classifications) and maximize their competitive potential.

Background: Soccer is a high-intensity sport characterized by a considerable incidence of injuries, particularly among professional male players, with injury rates ranging from 5.9 to 9.6 per 1000 player-hours. Lower limb injuries, including those affecting the knee, ankle, hip/groin, and hamstring muscles, are particularly prevalent. Additionally, a history of prior injuries may exacerbate the risk of recurrence. In response to these concerns, various injury prevention programs have been developed and implemented, targeting different genders and age groups. Methods: This systematic review and meta-analysis, conducted with the PRISMA guidelines, critically evaluated randomized RCTs across diverse genders and age groups to assess the efficacy of multi-component exercise-based injury prevention programs in reducing musculoskeletal injuries among soccer players. Comprehensive searches were conducted in ClinicalTrials.gov, CENTRAL, EMBASE, PubMed, Scopus, and Web of Science, with no language restrictions applied. Results: A total of 15 RCTs met the predefined inclusion criteria. The intervention programs were found to be significantly effective in reducing lower limb injuries, with a pooled RR of 0.73 (95% CI: 0.63 to 0.84, p = 0.035). Subgroup analyses further revealed a significant reduction in the incidence of hamstring, knee, and ankle injuries following the implementation of these programs. Conclusions: Multi-component exercise-based injury prevention programs demonstrate considerable efficacy in reducing musculoskeletal injuries in soccer players, spanning various age groups and genders. These findings underscore the potential of such programs in professional soccer injury management and highlight their importance in the development of comprehensive injury prevention strategies.

The kinematic and kinetic performance of tennis players differs across skill levels, with joint range of motion (ROM), moments, and stiffness being strongly linked to injury risk. Focusing on the biomechanical characteristics of lower-limb joints throughout the landing stage, especially among athletes of different skill levels, aids in understanding the link between injury risk and performance level. This study recruited 15 male campus tennis enthusiasts and 15 male professional tennis players. The kinematic and kinetic differences between amateur and professional players during the landing phase of the tennis serve were analyzed using SPM1D 0.4.11 and SPSS 27.0.1, with independent-sample t-tests applied in both cases. Throughout the tennis serve’s landing stage, the professional group exhibited significantly greater sagittal plane hip-joint stiffness (p < 0.001), horizontal plane moment (59~91%; p = 0.036), and a significantly higher peak moment (p = 0.029) in comparison with the amateur group. For the knee joint, the professional group exhibited significantly larger ROM in flexion–extension (0~82%; p = 0.003); along with greater ROM (0~29%; p = 0.042), moment (12~100%; p < 0.001), peak moment (p < 0.001) in adduction-abduction; and internal–external rotational moments (19~100%; p < 0.001) were markedly higher. The professional group showed significantly higher ankle joint ROM (p < 0.001) and moments (6~74%; p = 0.004) in the sagittal plane, as well as greater horizontal-plane ROM (27~67%; p = 0.041) and peak moments (p < 0.001). Compared with amateur tennis players, professional tennis players exhibit greater ROM, joint moments, and stiffness in specific planes, potentially increasing their risk of injury during the landing phase.

Background: The open-stance forehand is a fundamental technique in tennis, playing a crucial role in competitive performance. Its execution depends heavily on lower limb coordination and neuromuscular control. Athletes of different skill levels often display distinct muscle activation strategies. This study employs non-negative matrix factorization (NMF) to analyze lower limb muscle synergy patterns during the forehand open stance across skill levels and explores their potential influence on stroke performance. Methods: A total of 30 tennis players, including 15 elite and 15 amateur athletes, participated in this study. Surface electromyography (sEMG) was used to record the activity of major lower limb muscles during the forehand open stance. Muscle synergy patterns were extracted using NMF, and K-means clustering was applied to classify synergy patterns. Independent sample t-tests were conducted to examine differences between muscle synergies. Results: Significant differences (p < 0.05) were observed in the spatial characteristics of each synergy component across different movement phases. However, temporal characteristics showed a significant difference only in Syn2 during the mid-phase of the backswing (BS) (56.2–60.4%) (p = 0.033). Conclusions: Elite athletes exhibited more optimized and stable muscle activation patterns, enabling more efficient coordination of major muscle groups. Based on sEMG decomposition and muscle synergy analysis, these activation patterns may contribute to improved stroke efficiency and energy transfer and potentially reduce the risk of sports-related injuries.

This study investigated upper-lower body coordination during the swimming start. Coupling angle mapping was applied to assess segmental dominance, coupling angle, and coupling angle variability across four dive-start phases in elite and sub-elite swimmers. Data were collected from twenty swimmers (ten elite and ten sub-elite), based on their three fastest maximal-effort dive starts. The continuous entry movement from air to water was captured in detail using a high-speed multi-camera system positioned above and below the water. Results demonstrated that coordination patterns varied across the four phases, with high similarity when the thigh dominated, such as during the flight phase. Notably, coordination during the on-block phase differed significantly prior to hand-off. Elite swimmers exhibited greater trunk dominance in the entry phase, facilitating a more horizontal dive-in, whereas sub-elite swimmers showed trunk dominance later, during the transition phase. In conclusion, the time required to reach a specific distance or phase does not necessarily indicate superior start performance. Swimmers must balance drag minimization during the dive-in trajectory with rapid entry to initiate stroking. All swimmers maintained a streamlined posture and predominantly employed thigh-dominant strategies, while variations in trunk-dominant coordination were observed during entry and transition phases. Occasional high coupling angle variability in elite swimmers may reflect individualized coordination strategies. These findings highlight the importance of individualised training to optimize start performance.