VIDEO-BASED MARKER-LESS TRACKING SYSTEM IN GAIT ANALYSIS

An alternative to the 30 motion marker-based optical camera capture is the Star Tracker 3D, a marker-less video-based tracking system. The aim of our study is to investigate the efficacy of the Star Tracker 3D. A series of gait analysis tests were carried out on ten subjects with a marker and marker-less tracking system simultaneously. The study suggests potential application in gait analysis in the academic classrooms and clinical settings where observations of anatomical motions can provide meaningful feedback

THE EFFICACY OF VIDEO-BASED MARKER-LESS TRACKING SYSTEM IN GAIT ANALYSIS

An alternative to the 3D motion capture is the marker-less 3D video tracking system. Though not rigorously tested yet, the 3D marker-less video tracker would break new grounds if it is possible of extracting similar kinematic parameters as the gold standard 3D marker based motion capturers. The aim of our study is to explore the feasibility of a video based marker-less system. A series of gait analysis tests were carried out on ten subjects with a marker and marker-less system simultaneously. The study suggests potential applications in gait analysis in the academic classrooms and clinical settings where observations of anatomical motions provide meaningful feedback

APPLICATION OF PRESSURE MEASURES TO PREDICT PROPULSIVE FORCES EXERTED BY THE HAND DURING SWIMMING

The aim of this study is to investigate the validity of the pressure method to predict propulsive forces exerted by the hand during swimming. The use of pressure measures has been developed to predict hydrodynamic forces acting on the hand in swimming; however, the method has not been validated during swimming. Three swimmers were asked to swim without a kicking motion against a counter-weight in a towing system and to keep their position the same. The pressure method predicted the mean propulsive force by 25±12% differences from the known weights. The difference may be due to the propulsive force due to the forearm. This study estimated the hand propulsions due to drag and lift forces reliably, which can be useful information for a swimmer and coach

KINETIC LINK - DOES IT EXISTS IN THE KUDA AND SILA SERVE KICKING TECHNIQUE OF SEPAK-TAKRAW?

The purpose of this study was to determine if the kuda and sila kicking technique exhibits the kinetic link theory of proximal-to-distal sequencing. Seven Qualisys ProReflex MCU 1000 cameras operating at 240 Hz captured nine highly skilled male sepak-takraw players performing both the kuda and sila service technique. The best kuda and sila serve kick based on the highest ball velocity, net clearance and ball placement accuracy was selected and analyzed for final analysis. Comparisons of angular velocity histories of the thigh, shank and foot segment showed comparable thigh, shank and foot angular velocity patterns. No differences were observed for thigh, shank and foot angular velocities at ballcontact. Moreover, angular velocity pattern indicated that the kicking sequence for both kuda and sila technique does not exhibit the kinetic link theory of proximal-to-distal sequencing, except for he initial 10% from toe-off. As such, the kinetic link theory should not be applied to describe the kicking patterns of both kuda and sila service techniques. The implication to sepak-takraw coaches is to work on the technique of a single segment leg action to produce maximum momentum prior to ball-contact

3D KINEMATIC ANALYSIS OF THE KUDA AND SILA SERVICE TECHNIQUE

The aim of this study was to identify differences in kicking kinematics between the kuda and service technique. Nine highly skilled male sepak-takraw players performed both kuda and sila serves. All trials were captured using seven Qualisys ProReflex MCU 1000 cameras operating at 240 Hz. The best kuda and sila serve (highest ball velocity, net clearance and ball placement accuracy) was selected and analyzed for final analysis. Comparisons of selected kinematic variables were made between the two techniques at ball-contact using the paired Student t-test (

DIFFERENCES IN GROUND REACTION FORCES WHEN PERFORMING THE SIDE-STEP CUTTING ACTION ON DIFFERENT INFILL DEPTHS

This study aimed to quantify differences in ground reaction forces (GRFs) when performing a side-step cutting action on artificial grass turf with two different infill depths. GRFXPeak (7.27 ± 2.7 N/kg vs. 9.00 ± 2.7 N/kg, p=0.00) and GRFYPeak (5.41 N/kg ± 1.4 vs. 6.15 N/kg ± 1.6, p=0.00) were significantly larger, but not GRFZPeak (28.26 N/kg ± 8.6 vs. 29.64 N/kg ± 9.3, p=0.58) when participants (n=17) performed side-steps on turf with greater infill depths. Larger GRFZPeak during heel-strike may be due to larger knee extension angle (39.7 deg ± 8.2 vs. 34.7 deg ± 8.5, p=0.03) while significantly larger GRFXPeak and GRFYPeak at the weight acceptance phase and push-off phase may be due to a larger knee extension angle in conjunction with the hardness of sand/rubber infills given the increased thickness as well as frictional components of the artificial grass turfs

JOINT LOADING WHILE PERFORMING A SIDE-STEP CUTTING MANOUEVRE ON ARTlClAL GRASS TURF WITH DIFFERENT INFILL DEPTHS

The aim of this study was to determine differences in the joint loadings when performing side-step action on artificial grass turf with different infill depths. Significant changes in the ankle inversion angle (Ankle angle Y; p=0.01; ES=0.73), ankle inversion/eversion moment (Ankle moment Y; p=0.03; ES=0.54) and ankle abduction-adduction moment (Anklemoment Z; p=0.01; ES=0.76) at GRFSeak suggests greater loadings, in particular, at the ankle jint when performing the side-step manoeuvres on artificial grass turfs with thicker infill depths; indicating that all of the lower extremity adaptations to execute the stepside occurs at the ankle rather than the knee. A change in infill depths will cause the body posture to adopt a change in technique when executing the side-step manoeuvre. It is possible that greater joint moments elicited could be of risk to the athletes

KNEE JOINT LOADINGS OF ATHLETES PERFORMING THE SIDE-STEP CUTTING MANOEUVRES UNDER TWO DIFFERENT CONDITIONS

The purpose of this study was to determine differences in knee joint loading of athletes performing the side-step cutting manoeuvres under two different conditions (fatigued vs. non-fatigued). Lower limb joint kinematics and kinetics of 12 inter-varsity soccer players (6 males and 6 females) performing side-step tasks in two conditions were quantified using 10 optical cameras and Kistler™ force-platform. Fatigue conditions elicited significantly higher sagittal knee joint loadings (Mext, FPeak_GRF_Z, FPeak_AP_GRF and ?°GRF_Z_IC) then non-fatigued suggesting that athletes when fatigued adopted different strategies to compensate the changes to their environment

ESTIMATING THE PEAK VERTICAL GROUND REACTION FORCE COMPONENT AND STEP TIME IN TREADMILL RUNNING USING MACHINE LEARNING - A PILOT STUDY

This study aims to investigate the efficacy of a stacking approach to estimate parameters in treadmill running. Nineteen participants ran on a treadmill at self-selected pace. Ground reaction force and kinematic data were collected. Stacking in machine learning was used to estimate the peak vertical ground reaction force and step time. Good agreement was observed in the test data set for predicted and measured values of the peak vertical ground reaction force component and step time where the ICC values were 0.85 and 0.99 respectively. This suggests stacking may be a feasible approach to estimate kinetic and kinematic parameters during treadmill running

EFFECTS OF PURTURBATIONS ON KICKING LIMB CO-ORDINATION DURING THE SEPAKTAKRAW SERVE – A PRELIMINARY ANALYSIS WITH COACHING IMPLICATIONS

The purpose of this study was to describe kicking limb joint co-ordination between sepaktakraw serve techniques and to establish the effects of a perturbation on joint co-ordination when executing serve skills of different complexity to determine if the intended perturbations are required during training. A total of 25 kuda and 25 sila serve trials, performed by a trained male sepaktakraw player, were captured using a high-speed optical camera system. Kicking limb joint co-ordination differs between technique possibly due to differences in kicking kinematics. When subjected to perturbations (not receiving an ideal ball position in mid-air because the ball is tossed by another player), it took a longer time to return to normal kuda kicking patterns. Even with perturbations, players made adaptations to the kicking limb co-ordination and this strategy is key for repeated successful serves to unknown ball tossed positions in mid-air for optimal performance outcome measures. It is therefore recommended that perturbations be included during training so that, when perturbations occur, servers will be more aware of how to re-adjust their kicking patterns most quickly at the next serve