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ANGULAR IMPULSE MOTION-EFFECTS ON FRONT-LEG TECHNIQUE IN CRICKET BOWLING
Get PDFThe purpose of this study was to analyse the joint angular impulse-effect on knee joint extension-flexion angle on a sample of bowlers, determining whether front-leg technique is predominantly dependent on local joint torques or non-local cumulative effects generated elsewhere in the kinetic link chain. Elite young fast bowlers (n=13) were recruited for a motion analysis of their bowling actions in a biomechanics laboratory. Their fast bowling actions were classified according to front-leg technique and their changes in front knee extension-flexion angle related to corresponding joint angular impulse motion-effects. The majority of bowlers (61.5%) bowled with a bent-leg lever. Only 3.4% of knee extension-flexion periods were subject to an active angular impulse motion-effect. This result implies that knee extension-flexion angle in fast bowlers is also dependent on motions occurring away from knee joint, remotely located in the kinetic link chain
IS BALL-RACKET CONTACT CONCOMITANT WITH THE MAXIMAL RACKET SPEED IN YOUNG TRAINED TABLE TENNIS PLAYERS?
Get PDFPrevious table tennis studies have broadly assumed the racket to reach its maximal speed at ball-racket impact but only few identified this instant experimentally. Hence, there remains a lack of information regarding the validity of this hypothesis and therefore a need to develop a strategy to identify ball-racket contact that can be implemented into future experimentations. A 3D motion capture system was used to measure racket movements of seven young talents (12.6 ± 0.8 years old) -a category that had not been tested yet- during topspin forehand and backhand drives. Ball-racket impacts were identified with a synchronized microphone. Maximal racket speed and sound peak occurrences were compared, and racket parameters (speed, orientation) were calculated at both events. Differences emerged when examining participants individually for forehand drives and over the whole cohort for backhand drives, with consequences on both racket orientation and speed between the two events. As it was shown that ball-racket contact is not always concomitant with the maximal racket speed, futures studies should add supplementary equipment such as a synchronized microphone to identify the exact impact time
COACHING ASSISTANCE BY PHASE-BASED PERFORMANCE EVALUATION FEEDBACK OBTAINED FROM A SINGLE SACRUM IMU
Get PDFThe main role of a swimming coach is to provide frequent feedback and efficient planning to swimmers during training sessions. Quantitative and objective performance evaluation can better assist the coach. Inertial measurement units (IMUs) are widely used for motion analysis in sports because they can detect a variety of performance-related metrics. In this study, we propose a new performance evaluation feedback using goal metrics extracted from IMU and investigate its effect on the swimmer\u27s weekly progress. The measurement was conducted once per week with 15 competitive swimmers for 10 consecutive weeks using an IMU worn on the sacrum. Each swimmer was asked to swim five one-way laps at maximum velocity in front crawl, and the coach recorded the lap times with a stopwatch, which served as the main representative of swimming performance. The swimmers were divided into two groups, an experimental and a control group, and the coach received phase-based feedback only for the experimental group. The feedback quantified the swimmer’s performance in each swimming phase (wall push-off, glide, strokes preparation and swim) and the whole lap in every swimming lap of the test. He then used the feedback to adjust the training for each individual and focus on the weaknesses identified. The results showed that the experimental group had significantly lower lap time (p-value \u3c 0.05) and higher performance regularity than the control group from the sixth training session. This study showed that phase-based assessment feedback can help swimming coaches to create a more efficient training plan through detailed quantitative assessment
CHARACTERISTICS OF THROWING MOTION OF OVERPOWERING FASTBALL COLLEGE PITCHERS
Get PDFThe purpose of this study was to compare the motion pattern of overpowering fastball pitchers. The throwing motion of eighteen male college pitchers were analysed using a motion capture system. This study focused on the movements of the pivot leg and the trunk during the preparatory phase. The overpowering fastball pitchers in the present study largely abducted the hip of the pivot leg and leaned the trunk toward the pivot leg during the preparatory phase. That these motions were seen during the preparatory phase would reveal that a key motion to get fast ball speed exist in the preparatory phase
BIOMECHANICS STUDENTS’ ACADEMIC PERFORMANCE BEFORE AND DURING THE COVID-19 PANDEMIC
Get PDFThis study examines students’ academic performance before and after the outbreak of the COVID-19 pandemic and associations with performance in introductory biomechanics. Two intact undergraduate biomechanics classes were retrospectively examined: One with in-person instruction (IPI) two semesters before the outbreak of the pandemic and one with online instruction (OI) two semesters after the outbreak of the pandemic. Class performance measures were not significantly different between instruction formats. The students’ GPA was significantly higher after abruptly transferring from face-to-face to online instruction. GPA for three semesters during the pandemic had no association with the biomechanics class performance (r = 0.29, p = 0.19). Therefore, GPA during the pandemic years should be used with caution or in combination with other assessments
COMPARISON OF REARFOOT INVERSION ANGLE AT INITIAL FOOTSTRIKE MEASURED FROM FRONT AND BACK VIEW VIDEOS
Get PDFCrossover running gait patterns can obstruct the measurement of 2D rearfoot inversion angle typically determined from back view video recordings. This study aimed to compare the rearfoot inversion angle at the initial footstrike of running measured from front and back camera views. Twenty healthy female runners were recruited and 2D kinematic analysis was employed to analyse 7 consecutive gait cycles. Rearfoot inversion angles measured from both front and back camera views were compared using paired t-test. Results showed that 6 participants (30%) displayed a crossover gait. There was a significant difference between the front (11.7° [10.1°, 13.3°]) and back (7.2° [4.7°, 9.8°]) camera views (p \u3c 0.001, d = 0.883). This indicates rearfoot inversion angle measured from the front and back camera views cannot be used interchangeably. While the method offers a possibility to measure rearfoot inversion angle from the front view, the results cannot be directly compared to those obtained from the back camera view. In conclusion, this study demonstrated that rearfoot inversion angle at the initial footstrike could be quantified from front view videos for runners with crossover gait
MARKERLESS VIDEO-BASED ESTIMATION OF 3D APPROACH VELOCITY IN THE JAVELIN THROW
Get PDFThe purpose of this study was to explore the usefulness of a markerless open-source human pose estimation algorithm, for estimating centre of mass (CoM) velocity in the javelin throw at three discrete time instances: the last right leg touchdown (RLTD), brace leg touchdown (BLTD) and release. Forty throws from four right-handed javelin throwers were simultaneously captured with two high-speed video cameras and a 16-camera marker-based Vicon motion capture system. For horizontal resultant velocity (Velhor), the method demonstrated excellent validity at RLTD, whereas at BLTD and release errors were notable. Based on these findings, CoM Velhor can be estimated using the proposed method with promising accuracy at RLTD. At BLTD and release, using a CoM segment model with arms in more optimized measurement conditions might further improve the accuracy
OMEGA-3 SUPPLEMENTATION ON MUSCLE ACTIVATION PATTERNS OF THE KNEE DURING HIGH-RISK MOVEMENTS FOR ACL RUPTURES
Get PDFThe purpose of this study was to evaluate the role of omega-3 supplementation on fatigue and neuromuscular activation patterns of the lower extremity during a drop vertical jump (DVJ) and cutting maneuver. Seventeen female soccer players were allocated to a placebo (n=7) or omega-3 (n=10) (2.4g/day) group and were assessed before and after an 8-week period. EMG of the vastus lateralis (VL) and biceps femoris (BF) was evaluated during a DVJ and cutting maneuver prior to, and immediately following, a sport specific fatigue protocol. A 2x4 RM ANOVA revealed statistically significant (p≤0.05) increases in VL activation 100ms before initial contact (IC) during each movement assessed, and 50ms before IC during the DVJ on both limbs in the placebo group following the intervention. A significant increase in VL activation in the non-fatigued state 50ms before IC was reported in the omega-3 group during the DVJ on the dominant limb, following the intervention. Subtle changes in group means, in the fatigued cutting maneuver on the non-dominant limb, indicate a potentially beneficial adaptation in percent activation (Pre: 31±5% Post: 42±12%) and rate of activation (Pre: 106±60ms, post 30±10ms) for BF activity during weight acceptance in the omega-3 group. In conclusion, omega-3 supplementation increased activation of the VL 50ms before IC during the DVJ on the non-dominant limb in the fatigued state, post-intervention; but had no further statistically significant impact on muscle activity or rate of activation, following the 8-week period
DIFFERENCES AMONG THE OVERHAND, THREE-QUARTER, SIDEARM AND UNDERHAND DELIVERY STYLES IN BASEBALL PITCHERS
Get PDFThe aim of the study was to clarify the biomechanical differences among the overhand (OS), three-quarter (TS), sidearm (SS) and underhand (US) styles of baseball pitching. About 700 pitches were videotaped using the 3D DLT method. The fastest pitch of each pitcher was used to establish criteria for the separation of the pitches into the four styles based on coaches’ observation and on trunk lateral tilt and upper arm elevation angles. Forty-nine pitches were selected for analysis, and classified into 18 OS, 10 TS, 10 SS and 11 US deliveries. Twenty-six kinematic and kinetic variables were calculated and analyzed. Trunk lateral tilt and upper arm elevation angles were significantly larger in the order OS-TS-SS-US. Ball velocity was significantly slower in the US group than in the other three. Significant differences were found among the groups in six kinematic and five kinetic variables. The slow ball velocity in the US group may have been causally linked to the significantly smaller forces and torques of the US group in relation to the other three
SYNTHESISING 2D VIDEOS FROM 3D DATA: ENLARGING SPARSE 2D VIDEO DATASETS FOR MACHINE LEARNING APPLICATIONS
Get PDFThis study outlines a technique to repurpose widely available high resolution three-dimensional (3D) motion capture data for training a machine learning model to estimate the ground reaction forces from two-dimensional (2D) pose estimation keypoints. Keypoints describe anatomically related landmarks in 2D image coordinates. The landmarks can be calculated from 3D motion capture data and projected to different image planes, serving to synthesise a near-infinite number of 2D camera views. This highly efficient method of synthesising 2D camera views can be used to enlarge sparse 2D video databases of sporting movements. We show the feasibility of this approach using a sidestepping dataset and evaluate the optimal camera number and location required to estimate 3D ground reaction forces. The method presented and the additional insights gained from this approach can be used to optimise corporeal data capture by sports practitioners