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RECOMMENDATIONS FOR MINIMUM TRIAL NUMBERS DURING WALKING GAIT
Get PDFIn a rehabilitation context, athletes may not be able to complete large numbers of trials during testing due to joint edema and pain. The purpose of this research was to determine the minimum number of trials needed to achieve a negligibly fluctuating temporal variance profile during walking gait. The time-series kinematics of the hip, knee and ankle were recorded from 10 participants, completing 11 trials each. The time-series variance of each kinematic variables were calculated for ten trials and used as a reference. Using a two-sample SPM1D {t} (α=0.05), all variance combinations (9, 8, 7, ... 3 of 11 trials) from the same participants were compared to the reference. Results showed a minimum of 7 trials were needed to achieve ’stable‘ kinematic variance during walking gait. This study provides evidence for selecting an appropriate number of walking trials in gait analysis, especially in early-stage rehabilitation for patients with joint pain or edema
DEVELOPMENT OF A TEST PROTOCOL TO IDENTIFY POTENTIAL RISK FACTORS FOR LOWER LIMB INJURIES IN BALLET DANCERS
Get PDFThe aim of the present study was to develop a test protocol to identify potential risk factors for lower limb injuries during ballet jump landings. Two ballet dancers, a beginner level and an advanced level dancer, participated in the study. The dancers performed multiple Sautés in first position, Grand Jeté, and Grand Pas de Chat jump landings on a plantar pressure mat on top of a force platform. The participants wore ballet slipper thongs, while a three-segment kinematic model of the foot was used to provide a more detailed understanding of foot posture during landings, and to investigate how the dancers adapted to the high foot/ankle loadings. Potential risk factors were identified as high free moment peaks, high impact velocities, and improper technique with missing turnouts during landings. Furthermore, there seems a potential to distinguish between dancers’ ability levels and associated injury risks
KINETICS OF SOCCER SIDE-FOOT KICKING WITH VARIED EFFORT LEVELS
Get PDFWe aimed to illustrate joint kinetics during submaximal effort of soccer side-foot kicking. Side-foot kicks with three effort levels (50, 75 and 100% effort levels based on maximal effort) of eight male university soccer players were captured at 500 Hz while intial ball velocities were monitored simultaneously. Kinetic differences (angular impulses due to resultant joint moments) were clearly illustrated for hip flexion and knee extension thereby supporting the interpretation that the velocity of the distal end of the leg (foot) is controlled in a context of a proximal to distal segmental sequential system similar to instep kicks. Moreover, among joint moments responsible for out of thigh-shank plane motion, hip external rotation moment was found to be systematically adjusted between three effort levels. Additionally, an inconsistent trend was observed for hip external rotation angular velocity, suggesting some kinematic change in particular for the contribution of hip external rotation likely occured in submaximal side-foot kicks
THE EFFECT OF GRIP POSITION ON UPPER LIMB ANGULAR KINEMATICS DURING TENNIS TOPSPIN DOUBLE-HANDED BACKHAND STROKES
Get PDFThe purpose of this study was to compare the effect of grip on upper limb angular kinematics of sub-elite tennis players during a topspin double-handed backhand while aiming crosscourt. Sixteen sub-elite right-handed tennis players performed double-handed backhand trials using two different non-dominant grips (eastern & continental). Upper limb trajectory data was captured using the Vicon motion capture system (250 Hz). Greater peak angular velocity was observed in the eastern grip at the dominant shoulder (flexion, extension, abduction, adduction) and non-dominant shoulder (extension), elbow (pronation) and wrist (flexion, ulna and radial deviation). Subsequently peak linear velocities for the racket head (horizontal), and upper limb resultant joint centres were greater in the eastern condition. Collectively, these data suggest that using the eastern grip in the non-dominant limb is more optimal for developing racket head speed, and may provide coaches relevant information for athlete development in double-handed backhands
IS THE KICK SERVE LINKED WITH PARS ABNORMALITIES IN ELITE ADOLESCENT TENNIS PLAYERS?
Get PDFThe purpose of this study was to compare lumbar kinetics in elite adolescent tennis players with and without pars abnormalities. A 3D motion capture system was used to capture lumbar spine kinetics while 24 right-handed elite adolescent tennis players (male = 14, female = 10, 9 players with pars abnormalities) performed kick serves. Players without pathology were found to have significantly greater peak lumbar posterior force (7.3 N/kg greater), left lateral flexion force (4 N/kg greater), right lateral flexion force (3.4 N/kg greater), flexion moment (2 Nm/kg greater) and left rotation moment (1.2 Nm/kg greater) during the drive phase. Interestingly, no differences were observed for peak kinetic values during the forward-swing phase. Those with pars abnormalities had lower lumbar loading overall compared with those without pars abnormalities
OPTIMIZATION OF FLIGHT DISTANCE FOR THREE TYPES OF JAVELIN TIP
Get PDFIn this study, optimization of javelin flight distance was carried out using a genetic algorithm. Javelin tips with three different shapes were designed within the confines of the regulations. The first design was that of a typical commercially available tip, whereas the second design was thinner and the third design thicker than the commercially available tip. The aerodynamic forces acting on the three types of javelin tip with respect to the angle of attack were calculated using a commercial solver. In the optimization study, the design variables were the initial conditions at release (determined by the thrower), and the objective function was the flight distance. The flight distance was calculated by numerical integration of the equations of motion. It was found that the flight distance for the thinner design was shorter than that for the other two types. The key to a longer flight distance is that in the first half of the flight the drag should be small (the angle of attack should be small) and in the second half of the flight the lift should be large (the angle of attack should be large)
CLASSIFICATION OF FOUR DELIVERY STYLES OF PITCHING MOTON IN YOUNG BASEBALL PLAYERS
Get PDFThe purpose of this study was to examine the release positions of the throwing arm and of the trunk in four delivery styles (overarm, three-quarter arm, sidearm and underarm) of the baseball pitching motion, and to identify criteria to define the four delivery styles based upon the positions of both the trunk and throwing arm (upper arm) segments. Thirty-four pitching motions were videotaped using the 3D DLT method. These motions were qualitatively classified by coaches’ observation into 15 overarm, 7 three-quarter arm, 7 sidearm and 5 underarm deliveries. The angles for the trunk lateral tilt and upper arm elevation in the global coordinate system were quantified, and regression analysis revealed a linear relationship between the two angles. Criteria based on these angles were developed that matched the coaches’ observations well, demonstrating that the baseball pitching motion could be quantitatively classified into the four delivery styles
RELIABILITY OF A NOVEL PRINTED PIEZORESISTIVE PRESSURE SENSOR
Get PDFPrinted pressure sensors have the potential to be useful for measuring pressure in a multitude of sports biomechanics applications. This study was a proof of concept of a novel printed piezoresistive pressure sensor array with the aim of assessing the reliability of the sensor. The relationship between the force applied to the sensor and resistance was well described by an exponential equation (r2 \u3e 0.962), which provides confidence in the piezoresistive nature of the response. This demonstrates that, with further refinement and development, the currently-designed pressure sensor array has the potential to measure pressure during field-based sporting movements. Further research and development are required to improve reliability and to test sensor performance under dynamic loading conditions similar to those typically experienced in sport
A COMPARISON OF A TUCKED BACK SOMERSAULT BETWEEN NOVICE AND EXPERIENCED ACROBATIC GYMNASTS: AN INERTIAL MEASUREMENT APPROACH
Get PDFThe purpose of the case study was to analyse and compare the kinematics of a backward somersault in acrobatic gymnasts. Four acrobatic gymnasts aged between 8-17 years participated in the study, as two paired partnerships. Kinematic data during a backwards tucked somersault were collected using an XSens Inertial system and whole-body joint angular kinematics were compared between experienced and novice gymnasts. Findings indicate that experienced gymnast produced slightly greater knee flexion and an increased ROM through the take-off phase and a greater adduction/abduction movement during arm swing throughout the somersault. The novice gymnast produced a higher range of flexion/extension and internal/external rotation in the shoulder during the preparation and take-off phases. This indicates that training should focus on developing temporal movement efficiency to enhance effective progression of acrobatic gymnasts
BACKSWING LENGTH AND SWING PATH TENDENCIES FROM AMATEUR GOLFERS
Get PDFThe purpose of this study was to identify if shorter backswings off the tee influence the ‘outside-in’ ball impact (i.e. tendency to slice, fade or pull). Participants motion data were obtained on a reduced-size driving range, using a SmartSwing driver club (3D data sampling at 1000 Hz). Findings from a representative sample of the amateur golfers’ population (N=13, 531 swings) indicate a pattern where a shorter backswing reduced the tendency for ‘outside-in’ (-17.8%) while increasing ‘parallel’ (+6.9%) and ‘inside-out’ ball impacts by (+10.8%). For golfers who suffer from repetitive overuse or ageing-related reduced range movement or back pain, shortening the backswing is a viable option when considering safety and risk of injury. The findings can help golf swing coaching, as well as competitive/strategic and recreational aspects of self-management