Sports Biomechanics最新文献

Tackling in Rugby Union is associated with most match injuries. New tackle regulations have been explored to reduce injuries, but limited quantitative evidence is available to inform any law changes. Using a novel tackle simulator, we investigated upper body loading under different tackling conditions: direction of approach (0° - frontal, 45° and 90° to the ball carrier direction) and side of body (dominant vs. non-dominant). Peak impact force between tackler and simulator , and head and upper trunk segment motions were measured from 10 male players. Impact load averages were 17% higher at (0°) compared with (90°), across the two different tackling sides (p = 0.093), with the highest impact force measured during dominant-side shoulder tackles at 0° (5.63 ± 1.14 kN). Trunk resultant accelerations were higher (+19%, p = 0.010) at 0° compared with 90°, with the highest resultant acceleration measured in frontal tackles with the dominant shoulder (17.52 ± 3.97 g). We observed higher head lateral bending around the impact when tackling with the non-dominant shoulder at 45° (p = 0.024) and 90° (p = 0.047). Tackling from an offset angle from frontal may be safer. Deficiencies in tackling techniques on the non-dominant side should be reduced.

In rock climbing, climbers use their arms to regulate their posture on the wall, which can lead to localised muscle fatigue. Evidence shows fatigue is the primary cause of falls, but little is known about how fatigue specifically affects climbing rhythm and hand movements. The present study examined climbing fluidity and hand movements on an indoor climbing wall before and after a specific fatiguing protocol. Seventeen climbers completed three repetitions of a challenging climbing route (21 on Ewbank scale) with different levels of localised arm fatigue. Climbers' movements were tracked using 3D motion capture, and their hand actions assessed using notational analysis. Seventy markers were used to create 15 rigid body segments and the participants' centre of mass. The global entropy index was calculated on the path of the participants' centre of mass. Climbers fell more often when fatigued, but there were no significant differences in hip jerk or global entropy index when fatigued. No significant differences were found between the number of exploratory or performatory hand movements with different amounts of fatigue. The results suggest that localised arm fatigue affects a climber's ability to prevent themselves from falling, but it does not specifically affect their fluidity.

The goal of this study was to evaluate the technical and physical adaptations to a data-driven 12-weeks training programs that incorporated recent findings from biomechanical studies on the diving save. Three-dimensional kinematics and kinetics were collected and analysed from 11 goalkeepers diving to save high (190 cm) and low (30 cm) balls at three occasions: twice pre-training and once post-training. Intraclass correlation coefficients were found to be excellent (>.7) between the pre-training tests, and there were no learning effects between them. Three-way repeated measures ANOVAs were used to evaluate the effect of dive side, dive height and training programme (pre- vs post-training) on normalised dive time [s·m^-1], average centre of mass (CoM) horizontal velocity [m·s^-1] and total power [W] generated at contralateral and ipsilateral push-offs. Compared to pre-training, the post-training results revealed greater average CoM horizontal velocity (+.82 m·s^-1, 95% CI = [.62, 1.02]) and power (+523 W, 95% CI = [313, 732]) at contralateral push-off. These adaptations caused a reduction in normalised dive time (- .008 s·m^-1, 95% CI = [- .014, - .002]) at post-training compared to pre-training. This translates to 42 cm more goal area coverage in a penalty situation.

This study examined the roles of each leg in generating linear and angular impulses during baseball pitching. Professional pitchers (n = 4) pitched from a force plate instrumented mound, and 6-11 successful fastball pitches were used for analyses. We compared linear and angular impulses across the back and front legs. Linear and angular impulses were calculated from ground reaction force (GRF) and moment about each global axis passing through the centre of mass (COM), respectively. Additionally, we analysed measures that control the moment: (1) GRF magnitude, (2) magnitude of the position vector from COM to the centre of pressure and (3) the angle between (1) and (2). We found that the back leg generated forward linear impulse and the front leg generated backward linear impulse for all pitchers. Surprisingly, we found that the back leg generated significantly greater positive angular impulse about a global leftward axis (from the mound towards first base) than did the front leg in all four pitchers. Furthermore, the back leg's moment about the leftward axis became positive after the magnitude of forward GRF decreased from its maximum, suggesting that the back leg's role transitioned from generating forward linear momentum to angular momentum.

This study examined the effects of fatigue on hamstring muscles and gluteus maximus passive and active shear modulus in hip extension (HE) and knee flexion (KF) at 20% of maximal voluntary isometric contraction performed until task failure. Measurements were taken before and after the fatigue tasks and the delta (post-pre) was calculated. No differences in the fatigue effects on passive shear modulus were seen between muscles nor between tasks. For the active shear modulus: a task × muscle interaction was seen (p = 0.002; η²_p = 0.401). The results for the tasks separately demonstrated only a significant effect for muscle in KF (p < 0.001; η²_p = 0.598), with different individual contributions identified between BFlh-SM (p = 0.006; d = 1.10), BFlh-ST (p = 0.001; d = 1.35) and SM-ST (p = 0.020; d = 0.91). The comparisons between tasks for each muscle demonstrated significant differences for SM (p = 0.025; d = 0.60) and ST (p = 0.026; d = 0.60); however, no differences were seen for BFlh (p = 0.062; d = 0.46). Therefore, fatigue effects induce different patterns on the hamstring muscles in HE and KF tasks when performed at 20% MVIC.

Currently, there are no validated field-based measures of bat speed in cricket. This study sought to validate a baseball bat-mounted sensor for use in cricketers. Nine professional female cricketers (19.9 ± 2.8 years, 166.6 ± 4.8 cm, 68.7 ± 8.6 kg) performed 40 swings across four shot types (Cut, Drive, Pull, Slog-Sweep). Bat speed from a bat-mounted sensor was compared to optical motion capture (MoCap). Bat speed differed between shot types and ranged from 52.8 to 87.9 km/h. Device accuracy was determined by Bland-Altman bias and precision. The Drive shot had the smallest bias (-1.0 km/h; 1.4%), followed by the Slog-Sweep (2.0 km/h; 2.7%), Pull (2.0 km/h; 2.8%) then Cut shot, (2.5 km/h; 3.9%). The Cut shot had the greatest precision (2.7 km/h; 4.1%), followed by Pull (3.4 km/h; 4.7%), Slog-Sweep (4.0 km/h; 5.3%) and Drive (4.4 km/h; 6.3%). Kendall's tau analysis showed that proportional errors increased with higher bat speeds for all shots except Pull, (p < 0.05). The evidence supports use of the sensor for bat speed among female cricket players for all shots between speeds of 52.8-87.9 km/h. Caution is warranted for additional shot types, and speeds outside the explored range.

Running over 'softer' surfaces is thought to lower the magnitude of impact forces. Current research is limited and inconclusive regarding the influence that transitioning between surfaces has on impact forces. Adult runners (n = 18) ran outdoors over a 50 m pathway that was half concrete and half grass at a self-selected speed. We recorded tibial acceleration from inertial measurements units and calculated resultant tibial acceleration for each step. We performed a three-way repeated measures ANOVA with Cohen's d effect sizes to compare resultant tibial acceleration among surface type (concrete, grass), transition step (preparation, response), and period (transition, steady state). We observed no significant interactions among surface type, transition step, and period for resultant tibial acceleration. We observed no significant main effect for transition step but observed that resultant tibial acceleration was significantly greater on concrete than grass and when transitioning compared to steady state, with small effect sizes. The increase in tibial acceleration during the transition period likely occurs across multiple steps when preparing or responding to a new surface. Runners that are concerned about experiencing higher tibial accelerations may want to consider running on softer surfaces and limiting the number of surface transitions during a training session.

Spatiotemporal kinematics represent a novel domain within surfboard sprint-paddling. Investigating the interplay between stroke characteristics and sprint-paddling speed can inform the development of effective training strategies for both female and male surfers. 31 competitive Australian surfers (n = 15 females, n = 16 males) performed two maximal 15-m sprint-paddling trials in a swimming pool. Split times (5-, 10-, and 15-m), stroke count, stroke rate, stroke length, and stroke phase distances (glide, pull, push, recovery) during acceleration and speed maintenance periods over the 15-m were measured. Regression analyses determined multiple spatiotemporal variables that strongly contributed to faster split times at all distances, including a sex interaction effect (r² = 0.749, 0.791, and 0.794 respectively). For all surfers, push distance during acceleration and pull distance during speed maintenance were indicative of faster split times. For male surfers, the pull distance during the full sprint-paddle effort was indicative of faster split times. No variables were indicative of faster times for female surfers. This indicated that the development of a technique which promotes longer propulsive distances (i.e. pull and push distance) and an additional investigation of the female surfer should be encouraged to further afford optimal sprint-paddling success in both sexes.

The purpose of this study was to determine the number of crank revolutions required to obtain stable mean values of sagittal plane biomechanics variables, and the between-session reliability of these variables, whilst cyclists used an aerodynamic position. Eighteen elite cyclists completed a 3-min maximal bout on a cycling ergometer. Lower-limb kinematic and kinetic data were captured using 2D motion capture and force pedals. Raw data were filtered using a 4th order Butterworth low-pass filter (6 hz) and interpolated to 100 points per revolution. The middle 60 revolutions of each trial were extracted and 37 discrete and 15 time-series variables were calculated. Mean stability was assessed in all participants, and between-session reliability was analysed in a subset of 11 participants. Sequential averaging indicated more revolutions to stability than iterative intra-class correlation coefficients. Crank kinetics were more stable than joint kinematics and kinetics. For stable discrete and time-series variables, 30 and 38 revolutions are recommended, respectively. Between-day reliability for all variables was moderate to excellent, and good to excellent for crank kinetics and joint kinematics variables. Hip flexion-extension and ankle dorsiflexion kinetics were least reliable. Researchers and applied practitioners should consider these findings when planning, and interpreting results from, cycling biomechanics interventions.

This study aimed to evaluate head kinematics experienced during skill progression pathways in Women's Artistic Gymnastics to inform post-concussion return to gymnastics protocols. A return to gymnastics framework, consisting of seven skill progression pathways, was developed. Twelve gymnasts were instrumented with mouthpiece sensors and performed two trials of each skill, if able. Sensors recorded data at 100 Hz and skill segments were extracted using time-synchronised video. Peak resultant linear (PLA) and rotational acceleration (PRA), rotational velocity change index (ΔRV) and peak resultant rotational velocity (PRV) of 1 Hz low pass filtered data were computed from skills. A mixed effects model evaluated differences in kinematic metrics across skills within pathways while adjusting for random effects of the participant. Stepwise increases in kinematic metrics occurred along backward and forward tumbling (floor) pathways but did not occur in other pathways. For instance, gymnasts experienced greater PLA and PRV during clear hip and back hip circle compared to giant. Moreover, skills performed early along respective pathways (e.g, Yurchenko timer (to back), Tsukahara timer (to back), handstand forward roll) were among the skills with the greatest PRA and ΔRV. Head kinematics associated with skill performance should be considered when developing return to gymnastics protocols.