Sports Biomechanics最新文献

The purpose of this study was to compare the frequency and duration of on-side and off-side strokes and stroke transitions between male and female canoe slalom athletes during international competitions. We analysed 33 International Canoe Federation World Cup, World Championship and European Canoe Association Championship canoe slalom race videos, from 2018 to 2020, frame-by-frame. We recorded drive durations and transition durations for each race run. We also recorded the frequency of different stroke types and transition types used in each run. Stroke timing parameters differed between female and male athletes. We found that female athletes performed a significantly greater proportion of switch transitions and on-side strokes. Male athletes performed a significantly greater proportion of cross transitions and off-side strokes. Male athletes performed significantly faster cross transitions. On-on and off-off transition durations were significantly faster than cross transitions, and cross transitions were significantly faster than switch transitions. Females had a significantly longer drive duration and lower stroke frequency compared to males. Overall, stroke and drive durations of on-side strokes and off-side strokes were not significantly different. This study identifies stroke technique differences between male and female canoe slalom athletes which can be used as a basis for future research and training.

Athletes use either an eight-step or a seven-step strategy to reach the first hurdle in the 110 m hurdles event. This study investigates the effect of step strategy on the hurdle clearance technique and spatio-temporal parameters of the four steps prior to hurdle clearance. Two-dimensional video data were collected in the sagittal plane from 12 male sprinters, grouped as seven-step (n = 6) or eight-step (n = 6) strategists. The take-off distance was 0.20 m further from the hurdle and the touchdown was 0.42 m closer to the hurdle for seven-step athletes. Additionally, seven-step athletes reduced the length of the final step before hurdle take-off by 0.14 m compared with the previous step, whereas the eight-step athletes extended their final step by 0.17 m. There was negligible difference between the mean horizontal velocities of the two groups throughout the hurdle clearance (0.02 m/s) or the approach time to the first hurdle from the block clearance (0.01 s). This presents an important first insight into the effect of the step strategy on the first hurdle kinematics. Our findings identify the take-off and touchdown distance parameters of the hurdle clearance technique, and approach step characteristics for a successful seven- or eight-step approach strategy to be employed.

The first objective was to test the validity, reliability and accuracy of paired inertial measurement units (IMUs) to assess absolute angles relative to Vicon and OptiTrack systems. The potential impacts of slow vs. rapid and intermittent vs. continuous movements were tested during 2D laboratory analyses and 3D ecological context analysis. The second objective was to test the IMUs alone in an ecological activity (i.e., front crawl) that encompassed the previous independent variables to quantify inter-cyclic variability. Slow and intermittent motion ensured high to reasonable validity, reliability and accuracy. Rapid motion revealed an out-of-phase pattern for temporal reliability and lower validity, which was also visible in 3D. Also, spatial reliability and accuracy decreased in 3D, mainly due to discrepancies in local maximums, whereas temporal reliability remained in-phase. For the second objective, inter-cyclic variability did not exceed 12° based on root mean square error (RMSE). Therefore, IMUs should be considered valuable supplements to optoelectronic systems if users carefully position the sensors in rigid clusters and calibrate them to integrate potential offsets. Drift correction by spline interpolation or normalisation of the absolute data should also be considered as additional techniques that increase IMU performance in ecological contexts of performance.

Research of non-contact anterior cruciate ligament (ACL) injury risk aims to identify modifiable risk factors that are linked to the mechanisms of injury. Information from these studies is then used in the development of injury prevention programmes. However, ACL injury risk research often leans towards methods with three limitations: 1) a poor preservation of the athlete-environment relationship that limits the generalisability of results, 2) the use of a strictly biomechanical approach to injury causation that is incomplete for the description of injury mechanisms, 3) and a reductionist analysis that neglects profound information regarding human movement. This current opinion proposes three principles from an ecological dynamics perspective that address these limitations. First, it is argued that, to improve the generalisability of findings, research requires a well-preserved athlete-environment relationship. Second, the merit of including behaviour and the playing situation in the model of injury causation is presented. Third, this paper advocates that research benefits from conducting non-reductionist analysis (i.e., more holistic) that provides profound information regarding human movement. Together, these principles facilitate an ecological dynamics approach to injury risk research that helps to expand our understanding of injury mechanisms and thus contributes to the development of preventative measures.

The aim of the study was to examine whether the width of the base of support (BOS) has an influence on early postural adjustments (EPA) and armed upper limb and COM kinematics during lunging. Eight elite female fencers participated in the study. The displacement of the centre of foot pressure (COP) and kinematics of centre of mass (COM) were recorded using force platforms. The kinematics of the wrist of the armed upper limb were obtained using a 3D accelerometer. The results show that EPA were characterised by a very small COP displacement (about 0.6 to 1.2 cm). The COP amplitude showed a tendency to decrease with an increase in BOS width under reaction time conditions. In contrast, a greater BOS width was associated with a significant increase in COM acceleration at foot-off and peak COM acceleration during lunging also under reaction time instructions. The kinematics of the wrist were not influenced by BOS. The results show that in elite fencers, the upper limb movement is dissociated from the whole body movement. We suppose that a small COP amplitude is a postural skill which is integrated into the lunging skill and might influence the acceleration of COM.