5954 research outputs found
Sort by
COMPARISON OF MARKER AND MARKER-LESS AUTOMATED MOTION CAPTURE FOR BASEBALL PITCHING BIOMECHANICS
Get PDFThe purpose of this study was to measure baseball pitching kinematics with a marker-less motion capture system and compare the results against marker-based measurements. A sample of 114 pitches were captured at 240 Hz simultaneously with a 9-camera marker-less system and a 12-camera marker system. The pitches were thrown by nine baseball pitchers (age 17.0 ± 4.0 yrs). For each trial, the data were time-synchronized between the two systems using the instant of ball release. Coefficient of Multiple Correlations (CMC) were computed to assess the similarity of waveforms between the two systems. Paired t-tests were used to compare differences between the two systems for 3 temporal and 18 kinematic measurements. The CMC for all eight time series analyzed were excellent, ranging from 0.90 to 0.99. Timing of events between the two systems varied by two frames (0.0083 s) or less. Angular positions differed between the two systems up to 14 degrees. Thus, the marker-based and marker-less motion capture systems produced similar patterns for baseball pitching kinematics. However, based on the variations between the systems, it is recommended that a database of normative ranges should be established for each system individually
NO DATASET TOO SMALL! ANIMATING 3D MOTION DATA TO ENLARGE 2D VIDEO DATABASES
Get PDFThis study outlines a technique to leverage the wide availability of high resolution three-dimensional (3D) motion capture data for the purpose of synthesising two-dimensional (2D) video camera views, thereby increasing the availability of 2D video image databases for training machine learning models requiring large datasets. We register 3D marker trajectories to generic 3D body-shapes (hulls) and use a 2D pose estimation algorithm to predict joint centre and anatomical landmark keypoints in the synthesised 2D video views – a novel approach that addresses the limited data available in elite sport settings. We use 3D long jump data as an exemplar use case and investigate the influence of; 1) varying anthropometrics, and 2) the 2D camera view, on keypoint estimation accuracy. The results indicated that 2D keypoint determination accuracy is affected by body-shape. Frontal plane camera views result in lower accuracy than sagittal plane camera views
ASSESSMENT OF A MARKLESS MOTION TRACKING METHOD TO DETERMINE BODY POSITION ON THE BIKE
Get PDFThis study compared body position on the bicycle using manual and automatically determined body segments during stationary cycling. High speed video (120 fps) was obtained from 14 cyclists using their own bikes on a stationary cycle trainer in a single session. Torso, hip, knee and ankle angles were measured in two positions of the crank (3 o’clock and 6 o’clock-dynamically) to determine body position on the bike. Significant differences (3-12°, d=0.38-1.92) were observed for all joints between the manual and automated method for both crank positions (except for the ankle at the 6 o’clock). Overall, the automated method overestimated torso and knee flexions and underestimated hip flexion and ankle dorsiflexion. The implications of these changes in terms of bike setup are to be determined in future research but it is unlikely that errors from the automated method will result in large changes in joint forces
LABORATORY VERSUS ECOLOGICAL RUNNING: A COMPARISON OF FOOT STRIKE ANGLE AND PATTERN ESTIMATION
Get PDFThe purpose of the current study was to evaluate the ecological validity of two previously developed laboratory-based random forest machine learning models and train two new ecologically valid models for the 1) prediction of foot strike angle (FSA) and 2) classification of foot strike pattern (FSP) from wearable insoles during running. The original models performed worse with track-surface running data inputs than in their original validation (prediction RMSE = 6.84° vs. 3.65°, classification accuracy = 79.5% vs. 94.1%). The new models, trained using track-surface data, improved the estimation of FSA (RMSE = 4.10°) and FSP (accuracy = 84.8%). To ensure estimation accuracy, future models should be trained with respect to the environment/conditions in which they will be implemented
FOREARM LOADING AND SYMMETRY DURING ARTISTICS GYMNASTICS VAULT TRAINING SESSIONS.
Get PDFVaulting places considerable load on the upper limbs which can be associated with pain and injury. This study aims to use forearm-mounted IMUs to quantify forearm segmental loading and symmetry when performing foundation to advanced-level vaults. Twelve artistic gymnasts (female, n= 6; male, n= 6) wore bilateral forearm-mounted IMUs while completing their vault training sessions. The peak resultant acceleration (PRA) for the leading and non-leading forearms during hand contact was calculated. Descriptive statistics (median and IQR) and symmetry index scores (SI%) were calculated between the lead and non-lead forearms. High asymmetrical loading during vault contact was identified for some Yurchenko (SI%= 3.7-37.6%), Handspring (SI%= 7.7-21.0%) and Tsukahara vaults (SI%= 2.0-28.8%). Limb asymmetries varied between skills and gymnasts, highlighting that individual screening is needed to identify gymnasts with higher injury risk
EFFECT OF A SIX-WEEK NEUROMUSCULAR TRAINING PROGRAM ON VERTICAL STIFFNESS IN HEALTHY HIGH SCHOOL DISTANCE RUNNERS
Get PDFAthletes, coaches, and health care teams know that preventing running-related injuries (RRI) and improving running performance are extremely important. Proactive neuromuscular training (NMT) is often included as a complement to running programs for this reason. The purpose of this study was to evaluate the effect of proactive six-week low-intensity NMT focused on proximal hip and thigh muscles on healthy high-school runners’ muscle strength, biomechanical stiffness, peak ground reaction force, cadence, and stride length. The study demonstrates that the NMT increased a runner’s total strength by 10.4% and knee extensor strength by 10.3%, showed no change in stiffness, cadence, or stride length, and showed a decrease in ground reaction force post-program by 1.3%. Results show the multivariable nature of RRI risk, and prompt further, more generalizable, evaluation
FORCE-VELOCITY PROFILING FOR SHORT ICE HOCKEY SKATING SPRINTS: EFFECT OF EXPONENTIAL FUNCTION
Get PDFA high-speed digital video camera can be used to obtain highly reliable short-sprint split times. Split time data can be used to estimate instantaneous position, velocity, and acceleration by fitting an exponential function to the known positional data yielding force-velocity (F-V) profiles that may provide more information than just sprint times alone. The purpose of this study was to evaluate the between-rater reliability of different exponential functions used to estimate instantaneous data. A high-speed digital video camera was used to obtain split times from eleven male high-school ice hockey players performing a 6.10 m sprint and a separate top speed test. Including an optimization parameter and using a player’s measured maximal horizontal velocity instead of estimating it tended to produce better between-rater reliability
WITHIN-SUBJECT REPEATABILITY AND BETWEEN-SUBJECT VARIABILITY IN POSTURE DURING CALIBRATION OF AN INERTIAL MEASUREMENT UNIT SYSTEM
Get PDFInertial measurement units (IMUs) are a valuable tool for field based sports research, but within- and between-subject comparisons may be affected by variation in the 0° position established by a standing calibration position. This study assessed within-subject repeatability and between-subject variability in IMU sensor orientations during calibration. Calibration posture was reliable within-subjects given standardised instructions (typical error \u3c 1.9°). Sensor angles relative to a global vertical axis had large between-subject ranges for upper spine (21–35°), lower spine (1–23°) and pelvis (11–35°), while lower limb segment angles had much lower variability (0-6°). Thus, a standing calibration posture is repeatable within participants given suitable instructions, however variability in standing posture may need to be accounted for before making between-subject comparisons, particularly with regard to spine and pelvis segments
INTERLIMB ASYMMETRIES IN GROUND REACTION FORCE TIME-SERIES DURING BI-LATERAL COUNTERMOVEMENT JUMPS
Get PDFPrincipal component analysis (PCA) of waveforms can provide useful information about biomechanical patterns throughout a movement. The purposes of this study were to 1) use PCA to identify interlimb asymmetries in the ground reaction force (GRF) time-series data of the left and right leg during a bi-lateral countermovement jump (CMJ) and 2) determine if asymmetries in GRF time-series were associated with CMJ performance. Eight female collegiate soccer players performed three maximal effort CMJ. PCA extracted five principal components (PC) scores, eigenvalues, and eigenvectors from the GRF data. PC2 scores differed significantly between two legs, but only PC3 scores were positively correlated with CMJ height. Future research should investigate whether identified asymmetries in GRF time-series data are associated with sport performance or injury risk
THE THREE-DIMENTIONAL PELVIC MOTION IN THE ACCELERATION AND MAXIMUM PHASES
Get PDFThe purpose of this study was to investigate the mechanism of pelvic motion in the acceleration and maximum velocity phases. Eleven male sprinters performed 30 m and 60 m sprints at maximal effort and captured sprint movement at 15 m and 50 m. The contact time was significantly longer, and the angular displacement of pelvic elevation on the frontal plane was significantly greater in the acceleration phase than in the maximum velocity phase. Additionally, the angular displacement of pelvic elevation on the frontal plane showed a significantly positive correlation with the contact time and the stance length in the acceleration phase. These findings suggest that the greater pelvic frontal plane motion in the acceleration phase could increase the contact time and longer stance length