Sports Biomechanics最新文献

Curved sprinting has been proposed as a relevant and specific skill for soccer players' physical performance. However, professional timing systems are not always readily available in less resource-constrained environments. To address this issue, the development of a low-cost and user-friendly smartphone application could have practical applications for team sports staffs. In this context, the objective of this study was to evaluate the validity and reliability of the My Jump Lab application for the measurement of the curved sprint performance test. Correlational, comparative, and Bland-Altman analyses were conducted to assess the validity and reliability of the application in comparison with the gold-standard device. The results demonstrated excellent concurrent validity (r = 0.97-0.99, p < 0.001), and acceptable reliability (coefficient of variation < 3%, intraclass correlation coefficient = 0.88-0.96). Bland-Altman plots revealed small biases (-0.015 s and -0.010 s for the 17-m and 8.5 m curved sprints, respectively) and narrow 95% limits of agreement (-0.04 to 0.01 s and -0.03 to 0.01 s), indicating string agreement and no heteroskedasticity. Although small but significant differences were observed between test and retest sessions (p < 0.05), the overall findings support that My Jump Lab is a valid and reliable tool for assessing completion time during the curved sprint test in the specified arc, offering a cost-effective alternative for applied sport settings.

Rhythmic gymnastics (RG) is an Olympic discipline that emphasises repetitive unilateral movements that may lead to musculoskeletal asymmetries. The present study aimed to investigate the lower limb asymmetries during drop vertical jumps (DVJs) in young RG athletes. Fifteen young RG athletes (Age: 12.15 ± 2.26 years; Stature: 148.89 ± 14.31 cm; Body Mass: 39.02 ± 12.26 kg; BMI: 17.11 ± 2.65 Kg/m2), performed DVJs by stepping off a box using their preferred and non-preferred limbs. Several performance variables (flight time, contact time, reactive strength index-RSI, power output) and specific peaks of the vertical ground reaction force (vGRF)-time profiles in distinct jump phases for each limb, were analysed. When athletes stepped off the box with their preferred limb, the concentric force generation (the third peak of vGRF) was significantly higher in the preferred than the non-preferred limb (p < 0.05). Conversely, when athletes stepped off with the non-preferred limb, the force absorption during the breaking phase (the second peak of vGRF) was higher in the non-preferred limb than in the preferred limb (p < 0.01). The asymmetries observed in force parameters highlight the impact of RG's training demands. Addressing asymmetries in RG training may promote musculoskeletal health. Future research should explore the neural mechanisms underlying these asymmetries.

The aim of this systematic review and meta-analysis was to compare the effects of squat (SQ) and hip thrust (HT) training on performance in lower body athletic tasks, across different groups. A comprehensive search was conducted up to 31 May 2024, using PubMed, Web of Science, Scopus, Google Scholar, and Embase. SQ training was found to significantly improve vertical jump height (VJH) but greater than the HT. Neither SQ nor HT training had a significant impact on horizontal jump distance (HJD), short sprint time (SST), short sprint performance (SSP) or change of direction (COD) performance. In 12 to 16 sessions subgroup, SQ training significantly improved VJH, showing a medium ES. However, in other subgroups, neither SQ nor HT exercises produced significant improvements in HJD, SSP, SST, or COD performance. Subgroup analyses corroborated these findings. Squat exercises are more effective in developing VJH, while alternatively, no conclusive preference can be made between the exercises for enhancing HJD, SSP, and SST markers. Neither exercise had a discernible impact on COD performance. Future research should focus on conducting higher-quality studies to better elucidate the specific effects of SQ and HT training, or a combination of the two exercises, on various performance metrics.

Due to the constant high physical strain on tennis players during a match, the effect of a prolonged serve game on torque, power and work of the shoulder external and internal rotations, as well as on serve speed and precision, was investigated. Eighteen male competitive tennis players performed shoulder external and internal rotations (90º of abduction) at 180 and 300º/s on an isokinetic dynamometer before and after 12 points with one flat serve plus forehands and simulated backhands. When comparing pre and post moments, torque and power decreased in external (0.41 ± 0.07 vs 0.39 ± 0.06 N.m/kg and 71.1 ± 27.3 vs 59.7 ± 27.1 W) and internal (0.54 ± 0.10 vs 0.50 ± 0.13 N.m/kg and 91.7 ± 30.7 vs 80.1 ± 38.1 W) rotations at 300º/s, with p ≤ 0.05. Serve speed decreased after the fifth and sixth point (142.0 ± 20.1 vs 132.5 ± 15.3 km/h) and between clusters 1-6 and 7-12 (141.7 ± 15.5 vs 134.9 ± 12.4 km/h), with p ≤ 0.01. Serve precision decreased at the fifth and eighth points, with the highest score recorded at the end of the game. Training should focus on improving players ability to maintain performance during consecutive points, enhancing technical proficiency.

This study examined the effects of dual-task (DT) running on lower extremity and trunk coordination variability and whether these effects differed across running speeds. Thirty-one asymptomatic recreational runners (18 males, 13 females; age 26.2 ± 6.9 years; BMI 23.6 ± 2.8 kg/m²) completed treadmill running trials under three task conditions: single-task (ST), DT withan easy cognitive task (DT-easy), and DT with a difficult cognitive task (DT-hard). Each condition included three speeds: 85%, 100%, and 115% of preferred speed. Coordination variability of lower extremity joints and trunk segments during stance was quantified using Vector Coding and Ellipse Area methods. Two-way repeated-measures ANOVAs showed significant main effects of task (p < 0.05), with lower coordination variability observed under DT-hard compared to ST conditions. Speed effects were also significant, with greater variability at slower speeds. No significant task-by-speed interactions were found, indicating that DT effects were consistent across speeds. These findings suggest runners exhibit reduced movement adaptability under cognitively demanding DT conditions. Evaluation and training protocols for runners may benefit from incorporating DT paradigms to better reflect real-world demands.

To develop and validate machine learning (ML) models for classifying Taekwondo Poomsae side kick (SK) performance using kinematic parameters and physical function characteristics. Forty collegiate Taekwondo Poomsae athletes performed SKs with both legs. Two models were developed: a kinematic model incorporating SK and pelvic tilt angles at face and maximal heights, and a physical function model including range of motion measurements and Y-balance test scores. Performance quality was assessed by an expert evaluator using standardised criteria. Five ML algorithms were tested, and their performance was evaluated using area under the curve (AUC) analysis. Random forest classifiers demonstrated excellent performance in both models (kinematic model: AUC = 0.930, accuracy = 89.3%; physical function model: AUC = 0.930, accuracy = 89.3%). In the kinematic model, SK angle at maximal height emerged as the strongest predictor. For the physical function model, Y-balance test composite score showed the largest impact. These findings represent a substantial improvement over conventional subjective assessment methods by providing quantifiable, objective classification with high accuracy. ML algorithms can effectively classify Taekwondo SK performance using both kinematic and physical function parameters. SK angle at maximal height and dynamic balance emerged as the most important predictors in their respective models, providing quantitative criteria for performance assessment.

Articular stress, discomfort exposure and the use handles that are not adapted to the task-specific grip during repetitive movements may increase the upper limb injuries risk during boat rowing. Therefore, the purpose of this study was to introduce and evaluate the impact of two individualised ergonomic handles on comfort, upper limb's biomechanics, and performance in scull rowing, compared to standard handles. These two individualised handle designs were based on the irregular hexagon, and one was further individualised with the rower's comfort feedback. Perceived comfort, upper limbs kinematics, and neuromuscular activity, as well as boat speed and power production were monitored for 13 elite rowers. The handles tuned on the rower's comfort feedback increased significantly comfort (9.63 ± 0.3) while maintaining similar performance level (4.22 m.s^-1 ± 0.18). The improved comfort (p < 0.001) and the increased wrist extension (p = 0.014) were associated with a better blade orientation feeling. However, the handle orientation setup needs further investigation. Except for Deltoideus Posterior, upper limb neuromuscular parameters, power production and speed were not influenced by the ergonomic handles. New irregular hexagon handle diameters were found for optimal comfort in scull rowing. We recommend individualising irregular hexagon shaped handles for scull rowers wanting to improve comfort.

Jumps are used to assess musculoskeletal health. This study investigates neuromechanical differences in single-leg jumps for maximum height and distance regarding propulsion and landing phases to identify joint- and muscle-specific deficits. Nineteen healthy women performed both jump types, with assessments including 3D kinematics, ground reaction forces, and electromyography (EMG). Joint kinematics and torques were calculated using OpenSim, and muscle synergies derived from EMG data using Non-Negative Matrix Factorization guided by Variability Accounted For (VAF) metrics. Statistical parametric mapping compared the centre of mass displacement, angular trajectories, joint moments, and neural commands between jump types. Maximal height jumps require greater hip joint effort and emphasise knee mechanics and pelvic misalignments in the frontal plane. During landing, height jumps impose higher demands on eccentric knee extension and pelvis list, whereas distance jumps necessitate increased lumbar extension torques. The reduced knee extension torque and increased knee, trunk, and hip flexion angles in distance jumps may protect the knee. Landing from height jumps promotes anterior pelvic tilt in the sagittal plane. The analysis shows that two muscle synergies reconstruct propulsion EMGs, while landing requires three, indicating increased complexity. These findings highlight the need for customised assessments targeting specific neuromuscular and biomechanical aspects of lower-limb function.

This study investigated the impact of training on stride-to-stride variations in adolescent runners. It was hypothesised that training would significantly affect the magnitude and temporal structure of stride-to-stride variability during running. Twelve competitive adolescent runners (age: 16.3 ± 0.81) performed two 8-minute all-out running tests on a 400-m track, once at the start of the off-season (R₁) and again after 6 weeks of structured training (R₂). The study measured stride variability using the coefficient of variation (CV), monofractal analysis (DFA-α), and multifractal spectrum metrics (W and W_Asym). No significant differences in CV and DFA-α between the two tests, suggesting stable magnitude and temporal structure of stride-to-stride variability in terms of monofractality. However, significant changes were observed in the multifractal spectrum, with a reduction in W and a shift in W_Asym towards more symmetrical values after training. These results indicate that multifractal dynamics are a more sensitive metric to evaluate the effects of training on stride-to-stride variations in adolescent runners. The reduction of both W and W_Asym leads to the assumption that alterations in neuromuscular control and adaptability in adolescent runners occurred due to training. Future research should further explore the utility of multifractal metrics in monitoring training progress and optimising performance in young athletes.

Excessive peak vertical ground reaction force (VGRF) during landing is a risk factor for anterior cruciate ligament injury. Identifying the physical characteristics associated with peak VGRF is essential for injury prevention. The relationship between peak VGRF and maximum voluntary contraction (MVC) of the thigh muscle is weak, possibly because MVC does not reflect the muscle strength exerted at the knee joint posture and timing when peak VGRF occurs. This study explored the relationship between peak VGRF during landing and the rate of torque development (RTD), a measure of the rapid generation of muscle force, assessed at three different knee joint flexion angles. RTD and MVC of the quadriceps and hamstrings were measured in 36 physically active adults (18 males) using an isokinetic dynamometer at 30° and 60° knee joint flexion angles, simulating the joint angle at landing, and at a conventional 90° knee joint flexion angle. Results showed a significant negative correlation between hamstring RTD at 30° knee flexion and peak VGRF (r =  -0.71, p = 0.001), but no significant correlations were found with others. Therefore, it is important to assess muscle strength at the posture and timing when peak VGRF occurs to reduce peak VGRF and prevent injury.