EFFECT OF APPROACH SPEED ON SOCCER SHOOTING PERFORMANCE

The purpose of this study was to investigate the effect of different initial conditions (approaching speeds) on soccer shooting performance (indicated by ankle speed at ball impact). Three initial conditions, including standing still, walking and running at self-selected speeds, were adopted for performing kicking. The results showed that the running condition, with the greatest approaching speed, led to the highest ankle speed for generating the fastest ball speed after impact. The current results will be used for building a mathematical model for simulating soccer shooting with various approach speeds

DIFFERENCES BETWEEN JUMPING AND SOMERSAULTING FROM A DIVING SPRINGBOARD: A SIMULATION STUDY

Maximum-height jumping and jumping for maximizing backward somersault rotations are simulated. The springboard is modeled by a rigid bar with point mass on the tip and a rotational spring on the other hinged end. The planar 4-segment human model is driven by torque actuators at the ankle, knee, and hip. Movement simulation begins from a balanced initial posture and stops at jump takeoff. The objective is to find joint torque activation patterns during board contact so that jump height or the number of backward rotations in flight (determined by takeoff kinematics) is maximized. Kinematic differences between jumps maximizing backward rotations and jumps maximizing height lie mainly in reduced knee angular velocity and consequently bent knees at takeoff. In addition, more significant hip f1exion torque/activation is found in jumps maximizing rotations than that in maximum-height jumps. With reasonable model assumption, this kind of information may be useful for athletic training

BIOMECHANICAL ANALYSIS OF THE ATTACK TECHNIQUE IN TAI CHI PUSH HANDS

Tai Chi (TC) is a form of exercise developed from the martial art folk traditions of China. The force used in TC includes different principles of mechanical advantage. Push Hands are more advanced movements of TC exercise. No studies on the biomechanics analysis of TC push hands have been published. To analyze the kinematics, kinetic and electromyographic characteristics of TC Push Hands, an experienced TC master was asked to exhibit TC and normal pushing against another person for three trials. The movements were videotaped and digitised using a motion analysis system combine electromyographic and two force plates. The results indicated that the TC master cannot push the opponent over in normal pushing. The COG trajectories, kinetics, and EMG patterns are very different in normal and TC pushing. It is concluded that TC pushing is more strategic than normal pushing because its technique requires much less effort to cause the opponent’s imbalance

BIOMECHANICAL ANALYSIS OF THE DEFENSE TECHNIQUE IN TAI CHI PUSH HANDS

Developed from traditional Chinese martial arts, Tai Chi (TC) exercise includes different forms and Push Hands which are more advanced movements. No biomechanical analyses of interactive Push Hands have been found. To analyze the kinematic, kinetic and electromyographic characteristics of Tai Chi Push Hands, an experienced master was asked to defend pushing by another person for three trials. The movements were videotaped and digitized using a motion analysis system combining electromyography and force plate data. The results indicated that a certain postural adjustment was adopted by the master. A clear shift of body weight from the front to the rear foot and larger mediolateral displacement of the center of gravity (COG) was observed. Low activities were in the upper body muscle groups, while higher electromyographic values were in the right rectus femoris and substantially higher activity in the left rectus femoris during the defense. It is concluded that the TC defensive technique includes postural adjustment which slightly changes the pushing force direction, and allows the rear leg to resist the incoming force

EFFECT OF SHOULDER STRENGTH ON THE FLIGHT DISTANCE IN THE STANDING LONG JUMP

The purpose of this study was to identify the effect of different maximum shoulder joint force to the standing long jump distance. A five-segment model connected by frictionless hinge joints in plane motion was established for simulating the flight phase, and was driven by joint torques. The results show that jump distances are generally linearly related to maximum shoulder joint torque from 20 to 160 Nm. Further increase in shoulder joint strength fails to enhance the performance. Furthermore, a complete model combining both the ground contact and flight phases of the standing long jump should be used in future studies

EFFECT OF ATTACHlNG STRING DAMPERS ON VIBRATION CHARACTERISTICS OF A TENNIS RACKET

The "damper", a small device attached to the tennis racket string-bed, is commonly used by tennis players with little scientific support for its functions. The purpose of this study was to clarify the effect of damper attachment on racket vibration characteristics. Two accelerometers attached at different locations were used to measure racket handle and string-bed vibration patterns with and without a damper. Ball-racket impacts were controlled by releasing the ball abve the racket for producing consistent impact intensity at four different locations. Although amplitudes of spring-bed acceleration could be reduced by the damper, vibration on the racket handle was not affected by the damper

HOW DOES ARM MOTION ENHANCE VERTICAL JUMP PERFORMANCE- A SIMULATION STUDY

The mechanisms enabling the arms to increase standing vertical jump height are investigated by computer simulation. The human models actuated by joint torque generators consist of four/five segments connected by frictionless joints. Simulation initiates from a balanced static posture and ends at jump takeoff. Joint activation timings are optimized to produce maximum Jump height. Jumping performance is enhanced by arm motion in increased mass centre height and takeoff vertical velocity, which contributes about 1/3 and 2/3 to the increased height, respectively. Arm swing also elongates the durations of hip torque generation and ground contact period. Theories explaining the performance enhancement caused by arms are examined. Because shoulder joint force due to arm motion does not precisely reflect in the changes of vertical ground reaction force, the force transmission theory is doubtful. The joint torque/work augmentation theory is accepted at the hip but not knee and ankle because only the hip joint work is considerably increased. Since shoulder joint work is responsible for around half of the additional energy created by arm motion, the pull/impart energy theory is also granted

THE VALIDITY OF USING VIRTUAL REALITY HEAD-MOUNTED DISPLAY FOR AGILITY TRAINING

Virtual reality (VR) provides a fully controlled environment with the potential of making sports training easier. However, to date very few studies concerned creating a locomotion training environment enabling multi-directional movements for mimicking realistic locomotion. This study aims to investigate the validity of using low-cost VR head-mounted display (HMD) for agility training in a virtual environment (VE) for ‘real-walking’ locomotion. Three male college participants (age: 24.00±1.00years, height: 1.68±0.09m, weight: 65.63±4.65kg) participated in this study. They were asked to complete two agility ladder training tasks: the forward and backward icky shuffle, in the real environment (RE) and VE. The correlations of the segment trajectories in the RE and VE were calculated, respectively. Moreover, the correlations of the segment trajectories between the two environments were also calculated. The z-test results show that no significant difference has been obtained in the consistency of the movements between the two environments. Also, high correlations in the segment trajectories were obtained between the virtual and real training environment. The results indicate that it is feasible to use VR HMD for agility training

BIOMECHANICAL ANALYSIS OF THE EVADING WITH PUSHING TECHNIQUE IN TAI CHI PUSH HANDS

The traditional Chinese martial arts, Tai Chi (TC), include different forms and advanced interactive movements called Push Hands. Very few studies on the biomechanics analysis of TC push hands have been published. To investigate the characteristics of Tai Chi Push Hands, an experienced master was asked to perform the ‘evading with pushing technique’ when he was pushed by another person for three trials. The master’s movements were videotaped and digitized using a motion analysis system combining electromyography and force plate data. The results indicated that the master lowered his COG, shifted his body weight to rear foot, twisted his waist to evade the push, and pushed back with the strength from the lower limbs. It is concluded that the evading with pushing technique is a efficient and effective way to strike back

KINEMATIC ANALYSIS OF THE SUPPORTING LEG BETWEEN DIFFERENT WEIGHT DIVISIONS IN THE ROUNDHOUSE KICK OF TAEKWONDO

The purpose of this study was to compare kinematic differences in the supporting leg between two weight divisions in the Taekwondo Roundhouse Kick. Collegiate Taekwondo athletes participated in the study and differences in maximum joint angles and ranges of motion on the supporting leg during executing the Roundhouse Kick were examined. The results showed significantly larger (