Sports Biomechanics最新文献

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.

Early upper trunk rotation during baseball pitching has been associated with higher upper-limb kinetics. However, its relationship with arm fatigue after repetitive pitching is unclear. This study aimed to investigate associations between upper trunk rotation kinematics and arm fatigue. A total of 14 healthy male pitchers (age 27.1 ± . 9.0 yrs) threw 45 pitches across three innings. Pitching mechanics and ball velocity were assessed using 3-D motion analysis (Vicon, UK) and Rapsodo (Rapsodo, USA). Subjective arm fatigue was assessed by CR-10 Borg scale, whereas grip and shoulder external rotation strength were evaluated before and after pitching sessions. Ball velocity and the timing of upper trunk rotation did not change significantly throughout the three innings. Three-inning pitching produced significant levels of subjective and objective arm fatigue. The onset timing of upper trunk rotation (OTUTR) had significant effects on CR-10 Borg scale and ball velocity. The magnitude of effect of OTUTR on ball velocity may be clinically significant. These findings suggest that the timing of upper trunk rotation may not significantly affect arm fatigue with relatively low pitch counts, and early OTUTR may lead to early reduction in ball velocity.

In cricket fast bowling, late swing can increase interception difficulty for opposition batters. However, little is known about the occurrence and cause of late swing. This study investigated ball kinematics and the effect of changing kinematics on late swing with new cricket balls. Markers were placed on the ball to track the trajectory and calculate kinematics u1sing a motion analysis system. Fast bowlers generated varying ball kinematics (linear velocity, angular velocity and seam orientation) and delivery trajectories. A random intercept linear mixed-effects model identified that decreasing ball velocity (release velocity: effect = 0.21, p = 0.051, and pitch velocity: effect = -0.27, p = 0.011) and increasing seam stability (release stability: effect = -0.02, p < 0.001 and pitch stability: effect = 0.02, p = 0.001) were associated with greater late swing. To achieve these changes and create late swing, bowlers can pitch the ball on a full length and impart a large amount of backspin on the ball. However, swing can be influenced by factors such as wind and ball composition and late swing may be difficult to control. Bowlers and coaches should develop strategies to generate late swing but recognise it may be unpredictable in some situations.

This study aimed to clarify the disparities in trunk rotation and attack arm movement and their effect on hand kinematics adjustments between straight-line (SL) and diagonal-line (DL) volleyball jump serves. Thirteen male professional volleyball players (age 21.53 ± 5.39 years, height 1.95 ± 0.06 m, body mass 86.48 ± 11.63 kg, experience 8.61 ± 3.47 years) performed SL and DL jump serve, with three-dimensional coordinate data captured using a motion capture system (200 hz). Paired t-test and statistical parametric mapping examined kinematic differences between the two serving directions. At ball contact (BC), the speed of the attack arm hand was significantly faster in DL (16.99 ± 1.36 m/s) compared to SL (16.37 ± 1.53 m/s), whereas the face angle was significantly smaller in DL (1.98 ± 11.75°) than in SL (17.60 ± 17.98°). Forward rotation angles of the pelvic and upper torso at BC were significantly greater in DL (28.47 ± 10.89°; 21.30 ± 10.25°) than in SL (18.27 ± 12.46°; 9.09 ± 14.41°). During the arm swing phase, the pelvic's forward rotation angles in DL were significantly greater than in SL at 42-72% spiking motion, and the upper torso's angles were significantly greater at 49-58% spiking motion. These findings underscore the importance of adjusting pelvic and upper torso rotations to control the hand's face angle when serving in the diagonal line.

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.

High jump is a power-demanding motor task. Jumpers extend the take-off leg joints with maximum effort, but kinetic requirements (i.e. torque/power) for each joint are unclear. Here we show the inter-joint differences in the kinetic exertion related to the flight height in high jump trials by 16 male high jumpers (personal best record: 1.90-2.35 m). For the knee joint, both maximum net power and maximum norm of torque were significantly and positively correlated with flight height, with a stronger correlation for maximum net power (r = 0.70) than for maximum norm of torque (r = 0.52). For the hip joint, maximum norm of torque was significantly correlated with flight height (r = 0.62), but maximum net power (r = 0.36) was not. Both torque and power exhibited the proximal-to-distal sequence (from hip to ankle). The norm of ground reaction force peaked almost simultaneously with the hip torque while external net power peaked with knee power. We suggest that the required musculoskeletal function of each joint differs even in the same task. We suggest that it may be effective to adapt the different training programme between joints to improve performance. Jumpers should prioritise torque exertion for the hip and power exertion for the knee.

This study aimed to synthesise the body of knowledge on kinematics, active drag and energetics determinants of energy cost variability in the breaststroke technique. Methodological procedures considering the standards for systematic reviews according to the '"Preferred Reporting Items for Systematic Reviews and Meta-Analyses"' were employed. Searches were conducted in four prominent databases. A total of 1,464 articles were identified, of which 201 met the eligibility criteria. After evaluation, 73 articles were included for synthesis in this review. The included studies had a mean score (± SD) of 9.14 ± 1.76 points regarding the quality assessment. The present review identified three distinct domains of variables: kinematics (including stroke kinematics and coordination parameters), active drag, and energetics. The findings underscored the pivotal role of stroke kinematics, including stroke rate, stroke length, stroke index, and intra-cyclic variations of velocity, in influencing energy cost during breaststroke swimming. Additionally, the analysis highlighted the significance of propulsive and non-propulsive phases, arm-to-leg timing, and buoyancy in breaststroke technique. Notably, breaststroke exhibited higher values of active drag, frontal area, and energy cost, while maintaining lower velocity compared to other swimming techniques. Overall, this synthesis of literature highlights the holistic nature of energy cost in breaststroke swimming.

This study examined the acute effects of different loading protocols on 180° change of direction (COD) performance in eleven male handball players. Participants performed a 10-0-5 COD test under seven conditions: without an external load, and with 3, 6, and 9 kg loads applied under two modes-assisted into the COD and resisted out of it and resisted into the COD and assisted out of it. While total COD time was not affected (p = 0.098; η² = 0.16), significant phase effects were observed (p < 0.001; η² ≥ 0.55). Loading protocols significantly influenced velocity, acceleration, and their distances from COD (p < 0.001; η² ≥ 0.37). Significant phase effects were observed for all step kinematic variables (p ≤ 0.037; η² ≥ 0.67), except contact time, and significant interaction (phase*condition) effects for all variables (p ≤ 0.004; η² ≥ 0.08), except for step frequency. Assisted-resisted protocols increased deceleration demands through higher COD entry velocities, displaying fewer but longer steps in the acceleration phase and greater steps taken during the deceleration phase. Resisted-assisted protocols decreased deceleration demands due to lower COD entry velocities, displaying shorter, but more steps taken in the acceleration phase, and fewer steps taken in the deceleration phase. These findings suggest that assisted-resisted and resisted-assisted loading protocols can be used to selectively overload specific phases of COD performance.

This study examined the effect of 6-week training to improve horizontal deceleration ability on sprint acceleration and countermovement jump (CMJ) neuromuscular performance (NMP) parameters. Twenty male soccer players were divided into the training (TRA), and the control (CON) group. Pre-and post-training players performed an acceleration-deceleration ability test (ADA) and a jump on a vertical axis dual force plate. ADA deceleration parameters were analysed using Kinovea Software. Distance-to-stop (DTS), time-to-stop (TTS), 20 m sprint time (t_20 m), CMJ parameters were measured at pre-post-training. The largest improvement was determined in the TRA in the t_20 m (effect size = 0.88). Despite the increase in the weight of the TRA, t_20 m was shortened by 5.62% in TRA and 1.91% in CON. Deceleration ability was evaluated with CMJ eccentric parameters. While the percentage change of eccentric peak force differed between the groups, eccentric peak power (11.84 vs. 14.57 W·kg^-1, ds: 0.72) and velocity (0.91 vs. 1.05 m.s^-1, ds: 0.70) increased. Accordingly, it was determined that the improvement in CMJ eccentric and concentric peak velocity was due to speed-based power output. The training improved the maximum horizontal deceleration ability and confirmed that concentric peak velocity, as well as CMJ eccentric parameters, is an important NMP determinant of horizontal deceleration ability.