Sports Biomechanics最新文献

Anterior cruciate ligament (ACL) injury is common in sports that include 'change in direction' tasks. The aim of the current study was to determine the association between T2 relaxation time (an indicator of ACL integrity) of the distal portion of the ACL sub-region, biomechanical loading factors of the ACL, sex, and sport status of the participants. Participants between 18 to 35 years performed unanticipated 'change in direction' trials at their maximal self-preferred speed. The maximal knee flexion angle and the valgus moment of the right knee during the weight acceptance phase were analysed. MRI data (T2 relaxation time) of the ACL was also collected. Among the independent variables involved in the linear regression model, the association of the valgus moment and sex were statistically significant (p = 0.01 and p = 0.001 respectively). In conclusion, the main finding of the study is that higher T2 was significantly associated with a higher valgus moment as acute response to the 'change in direction' tasks. New sentence: In conclusion, the main finding of the study is that higher T2 was significantly associated with a higher valgus moment during 'change in direction' tasks.

We analysed the long-term adaptations of resisted sprint training (RST) with combined loads on the performance and kinematics of the maximal velocity (MV). One team women's professional soccer players performed a six-week training programme with progressive sled loading from 20% to 80% of body mass. Pre-training, post-training and detraining measures were obtained for sprint times for 0-20 m, 20-30 m and 0-30 m, while step length (SL), step rate (SR), step velocity, trunk, hip, thigh, knee, shank ankle, foot and centre of mass (CoM) angles were digitised with an 18-point human model. Two points were included: toe-off and touchdown, and both legs ipsilateral and contralateral. Sprint times were significantly reduced in the acceleration and MV phase, with a homogeneous individual response within the group. There were no significant alterations in the angles of the trunk, hip, thigh, knee, shank, ankle and foot across the different tests, nor in SR. Significant alterations in CoM-angle, step velocity and higher SL were observed. RST with progressive of combined loads effectively improved MV performance without causing changes that generated an adverse effect on sprint kinematics. The study offers an RST training programme to enhance sprint performance in professional female soccer.

It is well-known among swimmers and coaches that the swimming speed of the underwater dolphin kick (UDK) is higher than that of the underwater flutter kick (UFK). This study aimed to clarify the differences in swimming performance between the two kicking styles in terms of kinematics, kinetics and muscle activity. Eight male swimmers performed UDK and UFK in a water flume at same effort levels. The three-dimensional motion analysis and measurement of surface electromyography for the left lower limb were performed. The fluid forces acting on the body and joint torques were estimated using Swumsuit simulator. As the results, the kick amplitude and range of joint motion were smaller for the UFK than for the UDK, and the muscle activity and the peak joint torques of the hip and knee were lower for the UFK than for the UDK. Furthermore, the estimated propulsion for both the downward and upward kicks was lower for the UFK than for the UDK. Therefore, our results suggest that the differences in propulsion between the two kicking styles, caused by the differences in movement and muscle activity, may influence the differences in swimming speed.

The interplay between individual capacities and group performance provides insights for different tasks and contexts. So far, little is known about the individual capacities of base and top gymnasts and mechanical efficiency during pair tasks of Acrobatic Gymnastics. This work aims to investigate: (1) the effect of the pair experience in the mechanical efficiency during a pair task; (2) the effect of the individual training experience in the gymnasts' individual capacities, and (3) the contribution of individual capacities and pair mechanical efficiency to the performance of a partner-assisted flight task. Twelve pairs from national first division and elite levels performed a pair task and individual tests and were divided into pair and individual experience levels. Results showed that experience improves the pair task efficiency and individual performances, with distinct implications for each role. Mechanical efficiency is crucial for partner-assisted flight, but the individual capacities of base and top gymnasts also have an important contribution, followed by mass differences, and the pair experience. Coaches should focus on understanding how different experienced gymnasts can combine their capacities to collaborate efficiently. Also, considering the predictable increase in top gymnast's mass over time, to improve technical efficiency and individual physical condition.

This study aimed to examine differences in isometric peak force (PF) at the start of the first pull, transition, and second pull phases of the clean, and determine their contribution in explaining the variance in snatch and clean & jerk (C&J) performance. Thirty-one national and international level male and female weightlifters participated. Isometric start position pull (ISPP), isometric transition position pull (ITPP), and isometric mid-thigh pull (IMTP) PF, along with competition performance, were analysed both in absolute and allometrically scaled terms. Partial Least Squares Regression identified a single latent variable explaining 81.4% of the variance in Snatch and 79.6% in C&J. ISPP PF alone significantly contributed to explaining the variance the snatch and C&J. For allometrically scaled values, a single latent variable accounted for and 62.8% variance in Snatch and 60.7% of the variance in C&J, with ISPP PF significantly contributing to the Snatch and approached significance for C&J (p = 0.056). These results underscore the importance of evaluating maximal force in the initial lift phase and suggest that training to enhance strength in this phase may be crucial for improving weightlifting performance.

This study investigated the relationships between performance and force-velocity (F-v) parameters obtained from a ballistic lower limb (BLL) and a 30-m sprint test in 24 adolescent elite footballers (13.2-15.1 years old). In the BLL test, normal ground reaction force and velocity were recorded by two force plates and a linear encoder, respectively, and take-off velocity (vto) at 0% of body mass was considered as performance. In the 30-m sprint test, raw velocity-time data were measured using a radar, and 5, 10 and 30 m sprint times using a timing gate system. Theoretical maximal force (F₀), velocity (v₀) and power (P_max) were determined using the Samozino's method. All sprint times were significantly correlated with vto (p = 0.004 to p < 0.001; -0.57 to -0.72), but no significant correlation was found between the respective F-v parameters ;(p = 0.152 to 0.913). As both tests assess explosive performance, players who can produce a high vto will also perform best in short sprints. However, the F-v discrepancies highlight the complementarity of these tests: the BLL test minimises the coordination and technical influences that can affect sprint performance in adolescents.

Despite the high incidence of knee injuries reported in non-professional sports, the implementation of specific training programmes aimed at mitigating the kinematic and kinetic factors associated with these injuries remains limited. To determine the effects of a tailored exercise programme on kinematic and kinetic variables during side-cutting activities. Fifty-seven physically active participants were randomised into control group (CG; n: 28) that received no intervention, and an experimental group (EG; n: 29), that performed an individualised exercise programme that included a combination of strength, neuromuscular, proprioceptive, eccentric training and whole-body vibration (WBV) exercises. Knee, hip and trunk angles, vertical ground reaction force (VGRF), force in the antero-posterior (AP) and medio-lateral (ML) axes, acceleration, contact time and impulse were assessed during three types of side-cutting, two open manoeuvres (30º and 45º - SC₃₀ and SC₄₅ -respectively) and one closed manoeuvre (45º - SC_45cl-). After the 12-week intervention, EG participants had lower knee extension during all side-cuttings, shorter contact time and lower acceleration, VGRF and impulse compared to CG during side-cutting manoeuvres. A tailored exercise programme could be an effective neuromuscular and biomechanical strategy to reduce risk factors for knee injury in healthy, physically active young people.

The orientation and rear legs have different roles in the spike jump (SPJ) in volleyball, yet the relationship between the jump height and kinetics of each leg remains underexplored. We aimed to clarify the relationships between jump height and kinetics of the orientation and rear legs in the SPJ. This study included 18 female college volleyball players. The experimental trial comprised an SPJ with a three-step run-up. The motion and ground reaction forces were measured using eight high-speed cameras and two force plates. Kinetic variables from the last foot contact to take-off were calculated, and their relationship with jumping height was examined. The results showed that the peak joint torques for ankle plantar flexion (r = 0.562, p = 0.015), hip extension (r = 0.684, p = 0.002), and hip abduction (r = 0.670, p = 0.002) of the orientation leg were significantly positively correlated with jump height. No significant correlations were found for the rear leg, except for the hip abduction torque (r = 0.538, p = 0.021). These findings indicate that interindividual difference in jump height are more strongly related to the kinetics of the orientation leg than those of the rear leg after final rear foot contact.

The aim of this study was to investigate the relationships between knee and ankle strength and horizontal deceleration performance following different sprint distances. Fifty-seven (n = 41male, n = 16 female) youth team-sports athletes completed: a) 5-m and 10-m horizontal deceleration ability (HDA) tests; b) concentric (60°/s, 180°/s) and eccentric (30°/s) relative peak torque (PT) measurements of the knee extensor (KE) and flexor (KF) muscles and the ankle plantarflexion (APF) and dorsiflexion (ADF) muscles in an isokinetic dynamometer. Pearson's correlation coefficients revealed that concentric at 60°/s and eccentric at 30°/s KE were mostly related to deceleration performance both in HDA_5-m (r = -0.50 to -0.61, p < 0.05) and HDA_10-m tests (r = -0.50 to -0.63, p < 0.05). Moreover, a significant correlation was observed between concentric APF and average deceleration (DEC_avg) measured from HDA_5-m test in both the dominant leg (DL) and non-dominant leg (NDL) (r = -0.52 to -0.53, p < 0.05), but not to 10-m horizontal deceleration performance. The current results indicate that deceleration performance varies in its demands on knee and ankle strength across different sprint distances. Athletes who frequently decelerate over short distances should focus not only on strengthening their knee strength but also on prioritising ankle strength.

Orientation angles are commonly used to describe complex angular motions of the body. Selecting the most appropriate rotation sequence for a given segment's motion is crucial. The purpose of this study was to develop a set of generalisable, primary axis-centric sequence selection strategies and to compare the lean direction-lean-rotation (LDLR) sequence, selected for thoracic motion during golf driving based on the strategies, with the conventional rotation-bend-side bend (RBSB) sequence in assessing the level of inter-angle cross-talk. The RBSB method consistently revealed a higher level of inter-angle cross-talk, with substantially larger bi-angle ICC values across all angle combinations. The rotation-side bend and bend-side bend pairs in the RBSB method exhibited the largest ICC values (≥0.837). In contrast, the rotation-lean and lean direction-lean pairs in the LDLR method showed the smallest ICC values (≤0.063). The RBSB sequence demonstrated significantly larger RMS angle ranges (p < .001), indicating a deterioration of the major angle and inflation of the minor angles due to cross-talk. The LDLR sequence realistically portrayed the axial rotation-dominant thoracic motion during the golf drive. The strategies outlined in this study can serve as general guidelines and substantially enhance the applicability of the orientation angle method.