Sports Biomechanics最新文献

Rugby Union place kicking is influential to match outcome. Previous research has analysed kicker motion prior to ball contact in detail, but ball orientation and the impact phase are typically ignored. This study aims to firstly identify the ball orientations used by international place kickers, and secondly to experimentally analyse the foot-ball interaction in trained kickers using different ball orientations. Overall, 25.5% of the international kickers used an upright ball orientation, 27.5% used a diagonal orientation and 47.1% used a horizontal orientation. However, ball orientation preference was not significant in predicting kick outcome in a binomial logistic regression model. To address the second aim, ball orientation was experimentally manipulated and lower limb and ball kinematics were captured using high-speed (4000 Hz) video. Whilst the impact location on the ball differed significantly between most ball orientation conditions, the impact location relative to the global vertical was largely consistent across all conditions. This was likely due to kickers adopting very consistent lower limb kinematics, although the shank and ankle angles at impact were affected by ball orientation conditions for some kickers. Impact durations also differed between some conditions, although this did not appear to affect the impact efficiency.

Preparatory lower-limb loading conditions may affect the jump-to-reach performance of soccer goalkeepers. This study investigated the effect of pre-jump lower-limb loading/unloading during bilateral knee flexion-extension movements on sideways jump-to-reach performance in 18 male collegiate soccer goalkeepers. Participants performed the two-choice (high and low targets) reaction-time single-leg jump-to-reach task under two conditions: without preparatory movements (no-prep) and with continuous alternating knee extension and flexion movements (prep). The 'go' cue was provided with different preparatory loading conditions during the pre-jump knee extension and flexion phases. Performance was assessed using three-dimensional kinematic data and ground reaction forces. A significant main effect of the preparatory condition was observed for the jump take-off time. Pairwise comparisons revealed that the jump take-off time was 3.4-4.4% faster when initiated during the knee flexion phase than the no-prep condition and the extension phase (p ≤ .028). Increasing lower-limb loading and downward body movement with knee flexion appeared to facilitate effective loading to take-off to reach the high target and faster downward-directed take-off to reach the low target, respectively. Pre-jump knee flexion movement could be utilised by soccer goalkeepers to facilitate faster take-off to maximise their chances of saving shots within the reach of single-leg side-jumping.

We aimed to illustrate kicking leg dynamics during submaximal effort soccer side-foot kicks. Side-foot kicks with three effort levels (50, 75 and 100% effort levels based on maximal effort) of eight male university soccer players were captured (500 Hz) while initial ball velocities were monitored simultaneously. Systematic regulation in joint kinetics (angular impulses) was clearly demonstrated for hip flexion and knee extension moments thereby supporting the interpretation that the final foot velocity is controlled in a context of a planar, sequential segmental system. Out of the thigh-shank plane motion (hip external rotation moment) was also found to be systematically adjusted. Kinematic contributions of knee extension angular velocity to the final foot velocity increased significantly in the maximal effort while that of hip external rotation reduced significantly, coinciding with a more straightforward approach-run. The adjustable range of the foot-ball interaction was found to be rather smaller in side-foot kicks. However, significantly smaller ball/foot velocity ratios in the two submaximal conditions suggested ankle joint fixation was manipulated towards ball impact. Players and coaches ought to recognise that the intensities of side-foot kicks were regulated by the motions within and without the thigh-shank plane alongside several kinematic changes.

The study aimed to clarify the difference in the support leg dynamics and its mechanical role in producing the interaction torque acting on the kicking leg knee between female and male soccer players. Three-dimensional motion (500 Hz) and the ground reaction force (1000 Hz) were captured during the instep kicking of twenty female and twenty male players. Powers due to the support leg knee joint torque and the interaction torque were computed. A significantly smaller positive power of the interaction torque due to the support leg action seen in female players concurred with a significantly smaller positive knee joint power in the support leg. In contrast, female players exhibited a comparable positive power of the interaction torque due to the kicking leg action. Female players had a unique, more inclined lower leg posture of the kicking leg to compensate for their lesser power of the interaction torque due to the support leg action, thereby achieving a comparable magnitude of the power of the total interaction torque. Based on the dynamic background, they maintain a comparable lower leg angular velocity to that of male players immediately before ball impact.

This study questioned the influence of unilateral physical impairment on controlling inter-limb coordination, notably the coordination symmetry. We investigated whether unilateral physical impairment and unilateral breathing preference led to motor coordination asymmetry in eleven elite Para swimmers during 10 times 25 m in front crawl incremented in speed. Multicamera video system and five inertial measurement units were used to assess arm and leg phases and to compute symmetry of arm coordination and of arm-leg synchronisation. Hierarchical cluster analysis was used to classify the different profiles of relationships between impairment, breathing and motor coordination symmetry. Unilateral impairment led to asymmetric arm coordination (~83% of time, mostly at fast speeds), which always occurred to the side of the affected limb and which was associated to the preferential breathing side (~53% of time), while arm-leg synchronisation remained mainly symmetric (66.7 to 86.1% of time). It could be advised to assess the influence of impairment side and breathing side preference on motor coordination symmetry (1) to understand how the Para swimmers functionally adapt to their impairment, (2) to ensure that the unaffected limb generates great propulsion, and (3) to ensure that breathing does not impair propulsion nor increase motor coordination asymmetry.

The objective of this study was to clarify the effects of fatiguing muscle contractions of the m. quadriceps femoris on kicking abilities of experienced soccer players. 16 male professional (n = 5) and amateur players (n = 11) performed kicking tests in two conditions (fatigue and control) on separate days in a randomised crossover design. The fatiguing protocol performed with the kicking leg consisted of 5 sets of 10 maximal voluntary concentric and eccentric knee extensions. Maximal voluntary isometric contraction force (MVIC), 15 hz/50 hz stimulation force ratio (force ratio), and kicking abilities were assessed before and after completion of the fatiguing protocol or rest (control). The fatiguing protocol successfully induced fatigue of 14.0 ± 2.7% (mean ± SE) reduced MVIC and 14.0 ± 3.7% reduced force ratio while no reductions occurred in the control condition. Between group difference showed ball speed declined 2.1 ± 0.95% more following the fatigue protocol compared to control condition. On the control day shooting accuracy improved by 13.3 ± 5.6% and was numerically impaired on the intervention day by 1.0 ± 9.2%. Despite this, no significant between group difference was observed in shooting accuracy (p = 0.18). The study demonstrated that fatigue induced by prior muscle contractions impairs maximal shooting speed, but we observed no significant impairment of shooting accuracy.

The purpose of this study was to clarify the relationship between the ground reaction force (GRF) in the horizontal plane and the mechanical energy flow in the torso during baseball tee batting. The batting motion and GRF acting on each foot of 30 collegiate baseball players were recorded using a motion capture system and two force plates. To measure the mechanical energy inflow into the torso from both hip joints, the mechanical power of the torso by the force and torque of both hip joints was calculated. The horizontal GRF variables of the stride foot were significantly correlated with mechanical energy inflow into the lower torso from the hip joint of the stride foot side. Conversely, the horizontal GRF variables of the pivot foot were not significantly correlated with mechanical energy inflow into the lower torso from the hip joint of the pivot foot side. Thus, these results suggest that exploring the posture easily to receive the horizontal GRF by the stride foot (i.e., optimisation of magnitude and/or angle of GRF acting on the stride foot) increases the mechanical energy inflow into the lower torso from the hip joint of the stride foot side during baseball batting.

Skating sprint performance is essential for competitive success in ice hockey; however, it is unknown which component of a skating sprint is most critical for development throughout the performance pathway. Fifty-seven Swiss male ice hockey athletes were subjects (National League [NL], n = 22; Under 20 [U20], n = 20; Under 17 [U17], n = 15). Athletes performed: on-ice 30 m skating sprint, countermovement jump (CMJ), squat jump (SJ), and isometric mid-thigh pull (IMTP) tests in a single day. Linear mixed models, effect sizes and 95% confidence intervals were used to compare sprint performance and CMJ, SJ and IMTP between each performance level, with a correlation matrix used to determine the influence of lower-body strength and power on sprint performance. The NL and U20 athletes were significantly faster and had greater performance in most CMJ, SJ and IMTP variables compared to the U17 athletes, indicating minimum standards of lower-body strength and power are required to optimise technical performance. Significant differences were observed between NL and U20 for 10-20 m skating sprint split time and CMJ concentric relative peak and mean force, and reactive strength index-modified. Therefore, flying acceleration (10-20 m) is likely the most critical variable for pathway progression, with relative concentric force production the greatest influence.

Dancers require exceptional postural control to combat mechanically unstable positions. Dancers are prone to developing fatigue, which may increase the risk of injury. We investigated the effects of a dance-specific fatigue protocol on static postural control in a passé stance in 15 healthy dancers. A 12-camera video motion analysis system and a force plate were used to collect kinematic and kinetic data. After fatigue, significant increases in centre of pressure displacement were observed in the anterior-posterior direction on both legs (4.13 ± 0.71 mm pre-fatigue, 5.57 ± 1.9 mm post-fatigue dominant; p = 0.005; 4.41 ± 1.19 mm pre-fatigue, 5.24 ± 1.16 mm post-fatigue non-dominant; p = 0.018) and the medio-lateral direction on the non-dominant leg (3.18 ± 0.49 mm pre-fatigue, 3.37 ± 0.57 mm post-fatigue; p = 0.033). Sway area was significantly increased in the non-dominant leg only (52.1 ± 19.6 mm² pre-fatigue, 64.1 ± 18.9 mm² post-fatigue; p = 0.006). Significant increases in joint excursion for both legs were observed at the hip in the sagittal and frontal planes and the knee in the sagittal plane. There were significant increases in excursion for the non-dominant ankle in the sagittal plane. Static postural control was significantly affected by the fatigue protocol; the dominant leg appears to be more resistant to fatigue than the non-dominant leg. Therefore, dancers should include stability training that induces fatigue to increase balance recovery.

For adults, increasing cadence reduces ground reaction forces, but a lower preferred cadence does not predispose adults to experience higher ground reaction forces. Pubertal growth and motor control changes influence running mechanics, but it is unknown if preferred cadence or step length are associated with ground reaction forces for pre-adolescent and adolescent runners. Pre-adolescent and adolescent runners underwent an overground running analysis at a self-selected speed. Mixed model multiple linear regressions investigated the associations of preferred cadence, step length, physical maturation, and sex on ground reaction forces, while accounting for running speed and leg length. Running with a lower preferred cadence or longer preferred step length was associated with larger peak braking and vertical forces (p ≤ .01), being less physically mature was associated with larger vertical impact peak force and vertical loading rate (p ≤ .01), and being a male was associated with larger loading rates (p ≤ .01). A lower preferred cadence or longer preferred step length were associated with higher braking and vertical forces and being less physically mature or a male were associated with higher loading rates. An intervention to increase cadence/decrease step length could be considered if ground reaction forces are a concern for an adolescent runner.