Sports Biomechanics最新文献

The hammer throw is a complex discipline event in track and field sports, where Principal Component Analysis (PCA) has been applied as a key tool to analyse the details of movement patterns and identify crucial factors that affect performance. Therefore, this study aimed to use the PCA to analyse the hammer technique considering the age and performance. Thirty-nine male and thirty-two female hammer throwers who competed in the European Throwing Cup in 2018 and 2022 participated in the study. Three-dimensional kinematic analysis was used to process temporal and kinematic parameters associated with the hammer technique. The best throw from each athlete was chosen for analysis. The PCA facilitated the reduction and connection of the analysed parameters. In both groups except women U23, we observed higher correlations in velocity increase, hammer amplitude, and timing variables (double support, single support, and total time) in Turn 4. Lastly, differentiation factors were identified for each group. It was observed that a low initial velocity during Turn 1 was common in both men's and women's categories. Under 23 men should minimise the single support in Turn 2, and women should improve the velocity increase in Turn 4 to increase throw performance.

Running-related injuries (RRIs) have been linked to high-frequency components of impact-related variables. The influence of running retraining interventions on low- (LoF) and high-frequency (HiF) components of impact-related variables remains unexplored. This study investigated the effects of different retraining strategies on LoF and HiF components of impact-related variables. Twenty-six habitual rearfoot runners completed four overground running conditions: no instructions (CON), forefoot strike (FOR), increased cadence by 10% (CAD), and a combination of both (CADFOR). Three-dimensional kinematics were recorded, while ground reaction forces were processed to separate LoF and HiF signals (10 Hz as cut-off value). Compared to CON, HiF impact peak was reduced in FOR (p <0.001, d = 2.0), CAD (p = 0.006, d = 0.6), and CADFOR (p <0.001, d = 2.3). HiF instantaneous vertical loading rate was significantly reduced only in FOR (p <0.001; d = 0.6) and CADFOR (p <0.001; d = 0.7). Notably, adopting a forefoot strike pattern reduced HiF components of impact-related variables nearly three times more than cadence increase alone. The combination of forefoot strike and increased cadence produced the largest reduction in HiF impact components, suggesting it may be the most effective retraining strategy for potentially lowering RRI risk.

In soccer, anterior cruciate ligament (ACL) injuries frequently occur during sidestep cutting (SSC) in pressing situations. This study examined the effects of soccer-specific pressing tasks on SSC kinematics and kinetics. Twenty male recreational soccer players performed a 90° SSC followed by three task conditions: the Normal condition, in which participants simply continued running; the Pressing 70% condition, in which they reached for a ball placed at 70% of maximal straddle width; and the Pressing 100% condition, in which they reached for a ball at 100%. Maximal straddle width was defined as the distance between the toes during maximally hip-abducted. Both pressing conditions simulated defensive pressing. Three-dimensional peak knee and trunk angles, ground reaction forces, and knee moments of the supporting leg during the first 50 ms of the stance phase were compared. Results showed that peak knee valgus and trunk lateral inclination angles, as well as peak knee flexion, valgus, and internal rotation moments, were greater in both pressing conditions. These findings indicate that simulating pressing tasks altered SSC kinematic and kinetic characteristics. Notably, variables associated with ACL injury risk increased under pressing tasks, suggesting that pressing situations themselves may represent a biomechanical ACL injury risk.

The purpose of this study was to systematically explore the key kinematic factors influencing swimming velocity during the underwater dolphin kick (UDK) using statistical parametric mapping regression. Twenty-one university swimmers (16 males and 5 females) had a personal best within 20% of the world record. This study adopted a quantitative cross-sectional experimental design to identify phase-specific relationships between kinematic variables and swimming velocity during UDK. Their performances were recorded and analysed using two-dimensional (2D) video analysis. Twenty-one regression models revealed six key kinematic variables significantly associated with UDK velocity: the mean vertical velocity of the fifth metatarsal phalangeal joint, maximum vertical velocity of the fifth metatarsal phalangeal joint, maximum knee angle, minimum knee angle, minimum ankle angle, and mean angular velocity of the knee. Increases in these variables corresponded to higher swimming velocity. These findings provide a detailed understanding of the phase-specific contributions of lower-limb kinematics to UDK performance and offer practical implications for optimising training strategies.

This paper summarises research on the biomechanical inter-relationships between motor and physical features in maximal-effort locomotion. It first addresses separately conducted motion analyses and physical measurements, and then discusses their integration. In running single-leg jump, the human-specific, highest jumping mode, movements induced by actions other than lower-limb extension, such as stance-leg pivoting and pelvic elevation, generate more than half of the effective energy directly contributing to centre-of-mass height, highlighting the relevance of human-specific morphological features. Some effective energy generation by non-extensor movements is common to other locomotion modes, such as sprinting and cutting. These non-extensor contributions to propulsion during maximal-effort locomotion suggest that the way locomotion is executed reflects general human morphological and mechanical properties. Among morphological and mechanical properties, this paper emphasises those passively related to motor execution, in particular, inertial properties and tendon stiffness, as potential determinants of individually optimised motor solutions. These passive properties exhibit substantial inter-individual variability even within a single population; for example, the highest recorded lower-limb moment of inertia was 1.7 times the lowest. Meanwhile, studies combining motion and mechanical/morphological measurements remain limited. The integration of different areas within biomechanics is suggested as a key to unlocking the principles underlying human motor performance.

Benchmark tests in competitive cycling identify talent, individualise training, and monitor performance. However, varying protocols often produce conflicting results, reducing comparability. Isometric tests are prevalent, but reliability and performance correlation are underexplored. Determine the test-retest reliability of benchmark test metrics in elite track sprint cyclists and their relationship to a performance outcome. Nineteen elite track sprint cyclists (12 males, 7 females) completed seven benchmark tests across two days: modified sit-and-reach; on-bike rolling seated maximum 6-s sprints; 3-s bilateral on-bike isometrics at 90° crank angle; 3-s prone bench pull isometrics; 3-s lumbar extension isometrics; 3-s seated off-bike isometrics; and modified plank endurance. For the performance outcome, a third session within 7 days assessed peak power using an inertial load cycle ergometer. All tests showed excellent measurement consistency (ICC_3,1 ≥ 0.92), with low systematic bias (p ≥ 0.063), though confidence interval varied due to modest sample size. High test-retest reliability was supported by low typical errors (CV 2.0-5.5%; 9.6% for endurance). Nine benchmark metrics, including bilateral isometric measures, showed moderate to excellent correlation with peak power output (r = 0.52-0.94, p ≤ 0.023); six remained statistically significant after Bonferroni correction (p ≤ 0.005). All benchmark metrics were reliable, with six strongly and statistically significantly associated with performance.

This study examined the effects of 8 weeks of low-to-moderate intensity plyometric training with optimal drop heights on maximal isometric strength, vertical stiffness, and reactive strength in junior male basketball players. Participants were randomly divided into training (n = 20) and control (n = 20) groups from 3 teams with same division in the state league. Before and after 8 weeks of training, the drop jump (DJ) and isometric mid-thigh pull (IMTP) tests were performed to evaluate force-time measures. The optimal drop height was determined as the height that provided the highest reactive strength index (RSI). The ground contact phase during the DJ was divided into 2 subphases, braking and propulsion, for a detailed analysis of force-time curves. The analyses revealed that plyometric training significantly improved RSI (p < 0.001, Cohen's d = 1.507), ground contact (p < 0.001, d=-1.255), braking (p = 0.001, d=-1.066) and propulsion phase (p < 0.001, d=-1.078) time. Significant improvements were observed in the peak vertical ground reaction force (p < 0.001, d = 1.715), peak centre of mass displacement (p = 0.005, d=-0.989), vertical stiffness (p = 0.004, d = 0.983). However, there was no significant difference in the jump height (p = 0.382, d = 0.267) and maximal isometric strength (p = 0.602, d = 0.147). Plyometric training provided improvements in reactive strength, vertical stiffness, but did not improve maximal isometric strength.

This study investigated the impact of grip width on kinematics and kinetics in the seated barbell shoulder press among resistance-trained men. Eleven participants (age: 25.9 ± 3.1 years, height: 180.4 ± 5.4 cm, body mass: 87.0 ± 7.9 kg) performed eight repetitions to failure with a narrow, medium and wide grip width. Statistical parametric mapping was used to analyse kinematics and kinetics during the entire concentric phase of the last repetition. The main findings revealed that narrower grips increased both load lifted, and shoulder, and elbow range of motion. Moreover, grip width influenced horizontal barbell forces throughout 100% of the lift, and joint kinetics during the initial 64% of the lift. Wider grips increased lateral barbell forces and reduced elbow net joint moments (NJMs), while narrower grips increased medial forces and reduced shoulder NJMs. These findings suggest that grip width modulates joint kinematics, NJMs and lateral barbell forces during the shoulder press. Based on our findings, practitioners can make technical adjustments according to individual training goals, or tailor execution to minimise pain or injury risk. For example, by increasing or decreasing loading of a specific joint or altering joint ROM according to the athlete's or patient's needs.

The purpose of the study was to assign rowers to different rowing events based on their demographics and rowing kinematics using machine learning models. A total of 55 elite athletes from the Chinese National Rowing Team participated, each instructed to row on a rowing ergometer for one minute at three stroke rates: 18, 26, and 32 strokes/min. Trunk and upper arm 3D kinematics were collected using an inertia measurement unit system at a sampling rate of 100 Hz. Trunk and upper arm segmental and joint range of motion were generated. Trunk segments and upper arm motion coordination were analysed using the vector coding method. Six supervised machine learning models were trained using the collected demographics and kinematic data to classify rowers' groups (i.e. coxed eight and single/pair event group). The machine learning models successfully classified rowers' groups, with the top-performing models (decision tree, extreme gradient boosting, and random forest) achieving high classification performance (accurate rate = 0.89-0.93). The rowing event assignment automated by machine learning may help coaches make more informed and objective decisions. By minimising subjective biases, this approach enhances the accuracy and fairness of athlete selection processes, thereby potentially optimising team composition and performance outcomes.

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.