Gaze and performance of an elite karate exponent: a case study

The choice of attacks by Karate exponents is not well understood but is of importance to coaching practices. This case study explores gaze tracking sequences prior to attacking and seeks possible associative actions performed by the karateka. One Malaysian Karate exponent with over 8 years experience in the National team volunteered to participate in a simulation match of 2 minutes while wearing the Mobile Eye glasses (ASL, USA). Gaze was recorded at 25 Hz and was synchronised with an additional camera (25 Hz) recording the performance from just outside the mat. Gaze fixations were manually coded along 6 different areas (head, above the head, chest, abdominal, arm and leg) of the opponent. Also performance tactics (attack or counter) and actions (lunges, kick, punch and blocks) by the participant were manually notated. Gaze fixation sequences were selected from the start of an action back to when fixation had stabilized after the last action. The sequences were then clustered using the longest common sequence method in the TraMineR package of R-project statistical software. The clusters, similar in fixations sequence and length, were then associated with the tactics and actions performed. In total 23 fixation sequences and a same number of actions were identified. The most frequent and longest fixations were concentrated around the body and head of the opponent. The dendrogram showed three major types of clusters. Type 1 was mostly associated with counter attacks (79%) that included punches (57%). The second and third clusters contained the same number of attacks as counters and were mostly associated with lunges (50%) and kicks (38%). Furthermore looking at the lengths of the sequences within each cluster, type 2 and 3 had longer lengths than type 1. Therefore, these two clusters could essentially be considered as one despite differences in eye fixation sequence. The counter chudan (punch to the body) technique was used the most (7 times) and is associated with cluster type 1. Attacking kicks (5 times) and backward lunges (5 times) on the other hand are associated with the combination of type 2 and 3. However, it is rather the length of the fixation sequence in between the attacks than the area of fixations themselves that was found to be associated with the actions by this karateka. Short fixation sequences evoke a fast punching response. This is likely due to pressured situations where the distance to the opponent was reduced quickly by an attacking opponent. While longer fixation sequences are followed by (evading) lunges and kicks to disrupt the opponent and keep distance from the opponent without a direct attempt to score

FACTORS CORRELATED WITH SEPAK TAKRAW SERVE SPEED

The purpose of this study was to provide a better understanding of what contributes to the speed of the ball during the serve. The serves of seven national elite players (24 ±2.9 y, 182 ±5 cm and 77.9 ±8.8 kg) were filmed during training sessions. Serve speed was measured by radar gun. Selected kinematic variables were calculated from digitised video of 10 to 20 serves per player. Correlation and regression analyses were undertaken. Serve speed was predicted by several different combinations of variables for subjects. Higher order predictors were most often foot-to-foot distance and height of ball at contact. Different instructions should be given to each individual elite athlete in order to improve their speed and consistency of serve

THE EFFECT OF DIRECT VIDEO FEEDBACK ON PERFORMANCE OF TENNIS SERVE

The purpose of this study was to examine if junior tennis players could improve their speed and accuracy of the serve by using direct video feedback. Ten intermediate junior tennis players completed 50 acceptable maximum effort serves, aiming to land the ball within a 1 m square area adjacent to the service box T-area. Time series design was used in the study as part of the analysis of the data. The results showed that when video feedback was given on test day 3, the accuracy of the serve improved on test day 4. Additionally more accurate services and more “acceptable” services were completed in the square. The implication of these findings is that direct video feedback is a good tool to use to enhance technique execution of the serve

INFLUENCE OF MUSCLE ACTIVITY ON SHOOTING PERFORMANCE IN ARCHERY: PRELIMINARY FINDINGS

The use of proximal muscle is advocated for consistent archery shooting due to higher tolerance for fatigue. Muscle activity was subject of investigation in several archery studies. But thus far variation in muscle activity has been ignored. This study presents the preliminary findings of the influence of proximal muscle activity and variation on score and arrow release speed in Archery. Subjects were three Malaysian National archers shooting 29-36 arrows from 70 meter distance. Surface electromyography (EMG) was recorded for triceps (bilateral), left deltoid and right trapezius muscles. Arrow release speed was recorded with a speed radar gun. Linear and curvilinear associations of muscle activation and variation with score and speed are presented. Findings show each archer has different muscle determinants influencing score and speed

Successful tactics in taekwondo during Sukan Malaysia 2012

Introduction: The aim of the present study was to analyse the tactics performed by winner and non-winner during Sukan Malaysia (SUKMA) 2012. At present, scientific information and notational analysis on tactical aspects by Malaysia’s taekwondo youth is non-existent. Methods: Sixty two male taekwondo athletes were included in this study. Video recording was taken of 55 matches from quarter final to final involving four weight categories (80kg). Notational analysis for all matches was done using SportsCode Pro 8.5.2. The variables coded were tactics (attack and defence), techniques, target area and point result. The total number of attempts and successful attempts were counted per category for winner and non-winner. Chi-square statistical method was used to compare the total number of successful attempts between winner and non-winner for each tactic. Results: The Chi-square result shows no significant difference between winners and non-winners for tactics used across all weight categories and matches for total successful attempts (x2=4.00, df=3, p<0.05), for successful attacks (x2=5.50, df=3, p<0.05) and for successful defence (x2=1.97, df=3, p<0.05). Winners have 343 total (attack and defence) successful attempts, out of that 192 for attacking and 151 for defending. Non-winner received 172 total (attack and defence) successful attempts with 116 for attacking and 56 for defending. Winners however, have higher percentage of successfulness in attack and defence compared to non-winners. From 2187 total attempts, winners’ successfulness is 9% for attack and 7% for defence. Non-winners have 2352 total attempts, achieving 5% successfulness for attack and 2% for defence. Discussion & Conclusion: The result shows no differences in tactics for both winner and non-winner. Even though non-winners attempt more than winners (total: 2352 vs 2187, attacking attempt: 1749 vs 1391 and defensive attempt: 603 vs 796), winners have higher successfulness in attacking and defensive tactics. Possibly, winners have a qualitative difference that could explain the higher percentage of successfulness in attacking and defensive tactics compared to non-winners. Further investigation should be done in the sequence and quality of attempts to understand more about successfulness of attempts in Malaysian taekwondo youth

A Finite Element Analysis of a Human Foot Model to Simulate Neutral Standing on Ground

The objective of the paper is to perform finite element analysis of a human foot model to study the dynamic behavior and the internal loading conditions during neutral standing on the planar ground. The foot structure is simulated to assist in the design of an instrumented shoe insole. Finite element model of a human foot was generated and the loading condition during neutral standing was used to evaluate the stress distribution. The comprehensive stress distribution of the human foot model subjected to several loading conditions can be specified by a computational model. The method of the research is by using computational tomography data of the bone and soft tissue structures of a human foot in developing a 3-D finite element foot model. An analysis was conducted to simulate the loading condition of human foot during neutral standing. A commercial CAD software package was used to generate the boundary surfaces and the solid models of all model components. The numerical stress analyses for the neutral standing of the foot model was done using a commercial finite element software package. Peak pressures were seen at the first metatarsal, fifth metatarsal, and under the heel. The foot plantar deformation of the neutral standing foot model was seen similar to the finite element foot model in previous literature. The present study offers a prior computational model, which is capable of estimating the comprehensive plantar pressure and is intended to aid researchers in investigating foot plantar pressure as well as to develop custom-made insoles

Correlation between Archer's Hands Movement While Shooting and its Score

In archery, the most critical time is a few seconds before the release of the arrows because the trajectory of the released arrows is dependent on the movement of the archers arm in the release phase. Archers uses two hands while drawing a bow, one hand to push on the bow riser and the other to pull the string. The archer's performance can be quantified through the analysis of the movement of both the archer's both arm while they release the arrow. In this paper, a study of archers’ arm movement while shooting using recurved bow is presented. In the experiments, university level archers shot six arrows per frame and each archers shot three frames each whilst wearing a dedicated small sized accelerometer in both arms. The generated data, in terms of linear acceleration, were streamed in real time to a computer wirelessly via Bluetooth. The sampling rate of the accelerometer was about 15 Hz. The forward-reverse, up-down, left-right motion of both arms as well as the score and the position of the arrow of each shot were recorded. A high score category is when an archer shot ten, nine, and eight points while three, two, and one points score is a low score category. The analysis of the data showed a correlation between the archers’ arm movement and their score. The linear acceleration pattern for a higher score is very similar to the lower score; however, the average time taken before release for lower scores is about one second longer than the average time taken for higher scores

Best methods and data to reconstruct paediatric lower limb bones for musculoskeletal modelling

In biomechanical simulations, generic linearly scaled musculoskeletal anatomies are commonly used to represent children, often neglecting or oversimplifying subject-specific features that may affect model estimates. Inappropriate bone sizing may influence joint angles due to erroneous joint centre identification. Alternatively, subject-specific image-based musculoskeletal models allow for more realistic representations of the skeletal system. To this end, statistical shape modelling (SSM) and morphing techniques may help to reconstruct bones rapidly and accurately. Specifically, the musculoskeletal atlas project (MAP) Client, which employs magnetic resonance imaging (MRI) and/or motion capture data to inform SSM and nonrigid morphing techniques, proved able to accurately reconstruct adult pelvis and femur bones. Nonetheless, to date, the above methods have never been applied to paediatric data. In this study, pelvis, femurs and tibiofibular bones of 18 typically developing children were reconstructed using the MAP Client. Ten different combinations of SSM and morphing techniques, i.e. pipelines, were developed. Generic bone geometries from the gait2392 OpenSim model were linearly scaled for comparisons. Jaccard index, root mean square distance error and Hausdorff distance were computed to quantify reconstruction accuracy. For the pelvis bone, colour maps were produced to identify areas prone to inaccuracies and hip joint centres (HJC) location was compared. Finally, per cent difference between MRI- and MAP-measured left-to-right HJC distances was computed. Pipelines informed by MRI data, alone or in combination with motion capture data, accurately reconstructed paediatric lower limb bones (i.e. Jaccard index > 0.8). Scaled OpenSim geometries provided the least accurate reconstructions. Principal component-based scaling methods produced size-dependent results, which were worse for smaller children.status: publishe

Minimal medical imaging can accurately reconstruct geometric bone models for musculoskeletal models

Accurate representation of subject-specific bone anatomy in lower-limb musculoskeletal models is important for human movement analyses and simulations. Mathematical methods can reconstruct geometric bone models using incomplete imaging of bone by morphing bone model templates, but the validity of these methods has not been fully explored. The purpose of this study was to determine the minimal imaging requirements for accurate reconstruction of geometric bone models. Complete geometric pelvis and femur models of 14 healthy adults were reconstructed from magnetic resonance imaging through segmentation. From each complete bone segmentation, three sets of incomplete segmentations (set 1 being the most incomplete) were created to test the effect of imaging incompleteness on reconstruction accuracy. Geometric bone models were reconstructed from complete sets, three incomplete sets, and two motion capture-based methods. Reconstructions from (in)complete sets were generated using statistical shape modelling, followed by host-mesh and local-mesh fitting through the Musculoskeletal Atlas Project Client. Reconstructions from motion capture-based methods used positional data from skin surface markers placed atop anatomic landmarks and estimated joint centre locations as target points for statistical shape modelling and linear scaling. Accuracy was evaluated with distance error (mm) and overlapping volume similarity (%) between complete bone segmentation and reconstructed bone models, and statistically compared using a repeated measure analysis of variance (p80% compared to complete segmented bone models, and improve analyses and simulation over current standard practice of linear scaling musculoskeletal models.status: publishe