Sports Biomechanics最新文献

Optimal postural control improves performance and reduces the risk of injury in futsal. In this context, wearable accelerometers may detect velocity changes of the centre of mass during a task, enabling the analysis of postural control in different environments. This work aimed to determine the influence of vision and dominance on unipodal static postural balance in non-professional athletes. Twenty-four university male futsal players performed a unipodal balance test to assess their body sway using a triaxial accelerometer. To assess dominance, the preferred limb for kicking the ball was considered, while vision was manipulated by asking participants to close their eyes during the test. Root mean square (RMS) and sample entropy (SaEn) of centre of mass variables were analysed. For statistical analysis, a multivariate analysis of variance model was used. Our results suggest an effect of vision, but not of dominance nor the interaction between vision and limb dominance. Specifically, a higher-acceleration RMS in the mediolateral axis was observed, as well as an increased SaEn in the three axes. To conclude, unipodal postural demand in futsal players under visual input suppression was not influenced by their limb dominancy.

The purpose of this study was to investigate the concordance of isokinetic bilateral strength differences of the knee extensors in single- and multi-joint movement tasks. One hundred and nineteen male athletes performed isokinetic legpresses at 0.1 m/s and 0.7 m/s as well as isokinetic knee extensions at 60°/s and 180°/s. Bilateral differences and directed bilateral differences (sign indicating the direction of the difference) were calculated for all measurements. Bland-Altman-Plots were plotted to investigate if the different conditions detect bilateral differences of the same magnitude. Additionally, concordance correlations for the directed bilateral differences of the different tests were calculated to investigate magnitude and direction. The results indicate poor to fair concordance between the bilateral differences in the legpress conditions as well as between single- and multi-joint tasks. The single-joint knee extensions displayed a moderate level of agreement. Bilateral strength differences in isokinetic movement tasks are dependent on movement velocity and the nature of the task (single- or multi-joint movement) in the lower extremities. Both the value and the direction of the strength differences show no clear pattern across the investigated measurements and cannot be used interchangeably. Therefore, to assess interlimb strength balance, multiple different tests should be performed.

The PULSE workload monitor (PULSE) is a commercially available, wearable device that assesses upper extremity kinematics and kinetics during overhand pitching with three metrics to improve pitching performance. The purpose of this study was to determine the inter-tester and intra-tester reliability of the PULSE metrics when applied by a lay consumer versus trained researcher. A total of 14 healthy, adult male (age: 44.21 ± 17.54 years) baseball players were fitted with the PULSE under two application conditions, participant application and researcher application of the device. Each participant performed seven pitches of three pitch types, including fastball, curveball, and change-up, per application condition. The protocol was repeated during a second session one week later. Intraclass correlation coefficients (ICC) were determined to examine inter-tester and intra-tester reliability of the PULSE metrics between placement conditions and across sessions. For all pitch types, inter-tester reliability (ICC > 0.758) and intra-tester reliability (participant application: ICC > 0.710; researcher application: ICC > 0.890) were strong, indicating that the device is reliable when placed by a lay consumer. Findings suggest that PULSE may serve as an easily accessible, wearable device for reproducing pitching metrics that can inform consumer training.

This study verified whether the level of gluteal activation during a controlled maximum voluntary contraction may discriminate functional performance in women. Forty-five moderately trained women were assigned to two groups based on the level of gluteal muscle activation on maximum voluntary isometric contraction (MVIC) tests in the dominant limb: higher gluteal activation (HG-n = 22) and lower gluteal activation (LG-n = 22), considering different situations: a) level of activation of the gluteus medius muscle (GMed), b) level of activation of the gluteus maximus muscle (GMax), and c) level of combined activation of the GMed and GMax muscles. The cut-off values for the allocation of participants to groups in each situation were established as a function of the median values of each data set. Functional performance was assessed using the shuttle run, triple hop test, and six-metre timed hop test (STHT). The level of significance was set at 5%. Cohen's d index was included to estimate the magnitude of existing differences. The HG showed significantly shorter times than the LG on STHT performance (p-values ranging from 0.03-0.04), with a moderate effect (Cohen's d = 0.60-0.68) in all situations. The level of gluteal activation could discriminate STHT performance in women.

Increasing the braking and amortisation forces during a countermovement jump (CMJ) increases the early-half concentric mean force (EMF) which can enhance muscle contraction velocity in the latter half of the concentric phase. This may negatively affect exertion force, owing to the force-velocity relationship and not increase the jump height. This study aimed to investigate the associations of the braking and amortisation forces during the CMJ with the latter-half concentric mean force (LMF). Twenty-seven men (age: 20 ± 1 years, body mass: 76.2 ± 8.3 kg, height: 173.5 ± 4.7 cm) with training experience who performed body mass CMJs and five loaded CMJs were included. We calculated the braking rate of force development (B-RFD), amortisation force (AmF), EMF, and LMF, as well as the theoretical maximum force (F0) and velocity (V0) of the force-velocity profile. Correlation analyses per variable identified significant negative correlations of B-RFD and AmF with the LMF, but not of B-RFD and AmF with the jump height. Additionally, V0 was significantly correlated with the LMF. Therefore, increasing the initial concentric force by increasing the braking and amortisation forces may not contribute to jump height owing to a decrease in the latter-half concentric force due to the force-velocity relationship.

It has previously been argued that science has only made a limited contribution to the sport of golf, particularly the human element. This lack of impact could, in part, be attributed to the absence of an appropriate theoretical framework in most empirical investigations of the golf swing. This position paper outlines an ecological-dynamical approach to golf science that is better able to capture the interactions among the many structural parts of a golfer, and the relations between a golfer, his or her equipment, and his or her surrounding environment than other theoretical approaches have hitherto. It is proposed that the conjoining of principles and concepts of ecological psychology and dynamical systems theory could make a significant contribution to the enhancement of knowledge and understanding of swing biomechanics, club design and customisation, and coaching practice. This approach could also provide a platform on which to integrate the various subdisciplines of sport and human movement science to gain a more holistic understanding of golf performance.

This study aimed to investigate the kinematics and kinetics differences in ground reaction force (GRF)-time profiles with uni- and bimodal curves (UNC and BIC) during the concentric phase of the drop jump (DJ). Twenty two male Physical Education college student who met UNC (N = 11) or BIC (N = 11) of the GRF-time profile of were recruited. Two force plates and eight infrared optical cameras were synchronised to collect the GRF and motion data during DJ from a 30-cm height. The Shapiro-Wilk test was used to assess the normality of data. The Wilcoxon test was used when data were not normally distributed. Otherwise, Independent t-tests were used to compare differences between the UNC and BIC groups for each dependent variable. The UNC group demonstrated shorter ground contact time, lower jump height, greater leg stiffness, greater peak power during the eccentric phase, less work during the eccentric and concentric phases, and greater hip and knee joint flexion and extension angle displacements (p < 0.05). No significant intergroup differences were found in reactive strength index (p > 0.05). The UNC and BIC of the GRF-time profiles can indicate whether athletes can practice DJ appropriately. UNC can be representative of a better DJ performance with an efficient stretch-shortening cycle function.

Despite the mechanical advantage of preparatory movements on the starting block, current evidence questions the start improvements of competitive swimmers with their relay techniques. Therefore, the aim of the present study was to analyse the kinetic and kinematic parameters of a successful relay start. Twenty national- and international-level swimmers performed several relay starts (n = 145) with their preferred technique (short or long-step start) over an instrumented OBS11 starting platform. Trials were classified as successful or non-successful depending on the 10-m times being faster or slower than their individual start. Linear Mixed Models outlined that successful relay starts were characterised (all p < 0.05) by a later (0.04 s) onset of the leg step, a lower (18%) horizontal force during the leg step, and a later (0.03 s) positioning of the hands at the lowest point of the upper-limb backswing. In addition, greater values for the maximal horizontal (12%) and vertical (9%) forces and faster horizontal (4%) and resultant (3%) velocities were detected when driving off the block. These characteristics were also dependent on the relay technique. Unlike individual track starts, swimmers with fast relay starts employed longer preparatory movements on the block to maximise the time of force application and thus the impulse.

The aim of this research was to determine the association between dry-land exercises and the start kinetics in elite swimmers. Fourteen swimmers (eight males and six females) included in a national team took part in this study. A fixed smith-machine was used to measure the maximal full squat strength (Smax). The height of squat (SJ) and countermovement (CMJ) jumps were collected with a contact mat. The ground reaction force of the kick starts in the three-dimensional axis (Fz horizontal; Fy, vertical; Fx, lateral) was obtained by an instrumented force plate in the starting block. Overall, the Smax showed a high and significant association with Fz (r = 0.60) and Fy (r = 0.87). Moderate and significant associations were found between Fy and SJ (r = 0.51) and CMJ (r = 0.57). While Smax in males showed high association with Fy (r = 0.77), the Smax for females showed greater association with Fz (r = 0.84). As conclusion, the full back squat seems to be the dry-land exercise with higher association with the kick start kinetics. While in males the full squat defines better the vertical component, for females it defines the horizontal one.