ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive
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SPORTS FLUID DYNAMICS: AERODYNAMICS OF SPORTS BALLS
Get PDFRecently, newer soccer balls named Cafusa, Teamgeist 2, and Jabulani were respectively produced from 32, 14, and 8 panels with shapes and designs dramatically different from those of conventional balls. The newest type of ball, named Brazuca, was produced from six panels and will be used in the 2014 FlFA World Cup in Brazil. There have, however, been few studies on the aerodynamic properties of balls constructed from different numbers and shapes of panels. Hence, we used wind tunnel tests and a kick-robot to examine the relationship between the panel shape and orientation of modem soccer balls and their aerodynamic and flight characteristics. We observed a correlation between the wind tunnel test results and the actual ball trajectories, and also clarified how the panel characteristics affected the flight of the ball, which enabled prediction of the trajectory
LOCOMOTOR CONTROL PATTERNS DURING THE POLE VAULT APPROACH PHASE
Get PDFThe aim of this study was to investigate the visual regulation of locomotion during the pole vault approach phase on athletes of differing skill levels. Seven well-trained athletes performed six jumps which were recorded and analysed. Pole vaulters utilised three locomotor control patterns. However, these were not associated with skill level. The non-stable nature of footfall Variability in athletes enforces the need for degeneracy in approach phase movement patterns. Coaches should include training exercises that require intentional use of visual regulation to aid athletes in achieving the flexibility to adapt to changing constraints during the approach phase. Athletes should be considered on an individual basis in order to effectively, efficiently and safely improve performance. Practical solutions are offered which provide examples of how individual locomotor patterns can be interpreted to inform the prescription of training interventions
RELATIONSHIP BETWEEN BALL IMPACT LOCATION AND JOINT ANGLE CHANGES FOR ONE-HANDED TENNIS BACKHAND GROUNDSTROKES
Get PDFThe purpose of this study was to investigate the effect of off-longitudinal axis and off-lateral axis ball-racket impact locations on racket and lower arm joint angle changes for one-handed tennis backhand ground strokes. Three-dimensional racket and wrist angular kinematic data were recorded for fourteen university tennis players. Off-longitudinal axis ball-racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion / extension angles during the period immediately following impad. Off-lateral axis ball-racket impact locations had a less clear cut influence on racket and lower arm rotations. This study has confirmed that off-longitudinal impacts blow the longitudinal axis cause forced wrist flexion and established that there can be large differences in forced wrist flexion from individual to individual
RELATIONSHIP BETWEEN MAXIMUM TOE FLEXOR MUSCLE STRENGTH AND ANTHROPOMETRIC VARIABLES OF THE LOWER LIMB AND THE FOOT IN CALLEGIATE ATHLETES
Get PDFThe purpose of present study was to indicate reference values of toe flexor strength (TFS), and its relation with anthropometric variables of the lower limb and the foot in collegiate athletes. Subjects were 68 male and 26 female of collegiate athletes. Subjects were measured maximum TFS in standing position. In addition, it were carried out anthropometric measurements. And muscle thicknesses were measured with a B-mode ultrasonic apparatus in triceps surae, tibialis anterior, abductor halluces, flexor hallucis brevis, flexor digitorurn brevis, and abductor digit minimi. TFS were in male and female collegiate athletes were 256.7f 55.8N and 207.3f 36.9, respectively. Stepwise multiple linear regression analysis revealed that important factors to determine TFS were the muscle thickness of flexor hallucis brevis muscle and body weight
LOWER BODY SIMULATION ANALYSIS ON INCREASING ROTATIONAL VELOCITY OF LOWER TRUNK IN BASEBALL TEE BATTING
Get PDFThe aim of this study was to investigate optimum timings of joint toques of the lower extremities in order to generate larger angular velocity of the lower trunk through baseball tee bating. A lower body seven-segment computer simulation model was developed. The model has totally 17 active torque generators at individual hip, knee and ankle joints, and torso joint. The optimisation procedure for the performance improvement was carried out by varying timings of exerting joint torques to maximise the peak forward angular velocity of the lower trunk about the vertical axis. The difference in exerting timing of the hip and knee joint torques of the stride leg contributed to increasing the peak angular velocity of the lower trunk, and that of the pivot hip flexion/extension joint toque prior to the impact contributed to the inhibition of the excessive rotational movement of the lower trunk
THE ELECTROMYOGRAPHY CHARACTERISTICS BETWEEN DIFFERENT LEVELS OF SOCCER PLAYER ON INSTEP KICKING
Get PDFThis study improves kicking performance by comparing muscle activity between different levels of players. Twelve soccer players in the college cup in division I and division II volunteered to participate in this study. A VlCON motion capture system (200 Hz) was used to capture the kicking motion including back-swing and forward-swing. The Noraxon electromyography system was used to collect and analyze the percentage of maximum voluntary contraction on rectus femoris, bicepsfemoris, tibialis anterior, and gastrocnemius. The Mann-Whilney U (a = -05) test was applied to assess significant differences in this study. The results indicated that division II players had a greater percentage maximum voluntary contraction in tibialis anterior in the back-swing. To avoid stiff movements in soccer kicks, division II players should decrease muscle contraction in the tiblalis anterior In the back-swing
THREE-DIMENSIONAL ACCELERATION DURING RUNNING IN TRAINED ATHLETES AND UNTRAINED SUBJECTS
Get PDFThe present study aimed to evaluate the three-dimensional (30) accelerations during running in trained athletes compared to untrained subjects. Ten endurance-trained male athletes and 10 untrained male subjects wore a 3D accelerometer at the L3 level and ran on a 400-m track at three different speeds. The acceleration amplitude was calculated for each direction from the acceleration time series for 10 strides. Additionally, the positive and negative peak values of vertical and anterior-posterior accelerations were calculated. Analysis of covariance tests showed a significant difference between athletes and untrained subjects in the vertical acceleration amplitude. Significant interaction effects were found for upward acceleration and forward-backward acceleration ratio. These results suggest that athletes have characteristic patterns in the vertical acceleration and forward-backward acceleration ratio
THE CENTRE OF MASS KINEMATICS FOR ELITE WOMEN JUDO ATHLETES IN SEOt-NAGE
Get PDFThe purpose of this study was to investigate kinematics of the whole body centre of mass (COM) in seoi-nags performed by elite and collegiate women judo athletes. Three dimensional coordinate data were captured using a Vicon-Mx system with 18 cameras operating at 250 Hz as 3 women elite judo athletes and 6 women college level judo athletes performed seoi-nage. No difference was found in motion time of the turning phase in seoi-nage between the two groups, indicating that motion time may not be a factor to determine the skill level of seoi-nage. The maximum Y relative velocity of the COM in seoi-nage was much greater in the elite women judo athletes than the collegiate judo athletes, which implied that the relative forward velocity of the COM would be an index to evaluate the skill level of seoi-nage for women judo athletes
SIMPLE INSTRUCTIONS ON THE CROUCH POSITION IMPROVE PERFORMANCE IN THE COUNTERMOVEMENT JUMP
Get PDFThe purpose of this study was to determine how simple instructions that modify the depth of countermovement lead to changes in the jump height and the biomechanical parameters related to centre of mass displacement and force application. Twenty-nine active males participated in this investigation and they performed three countermovement jumps using a self-selected crouch position, three countermovement jumps with a deeper crouch position and three countermovement jumps with a shallower crouch position in random order. The results of this study suggest that is possible to improve the jump performance in amateur competitive males with slight modification of the centre of mass displacement having the same physical condition level without any training intervention
KINETIC ANALYSIS OF START MOTION ON STARTING BLOCK IN COMPETITIVE SWIMMING
Get PDFThe aim of this study was to investigate kinetic features of start motion with use of an instrumented starting block. This is the first study that quantified joint torques of the whole body during start motion. Six male swimmers dived from the instrumented starting block, which contains force plates and sensors. Four high-speed cameras were used to obtain kinematics data of the swimmers. Inverse dynamics calculation was carried out with use of the kinetics and kinematics data. The results showed that 1) the large pulling up forces exerted by both hands were generated by extension toques of the shoulder joints, 2) the rear side lower limb joints exerted large extension torque to obtain horizontal reaction force, and 3) the knee joint of the front side lower limb exerted large flexion torque to maintain the large vertical reaction force until 60% normalized start motion time