ISOKINETIC EVALUATION OF SHOULDER INTERNAL AND EXTERNAL ROTATORS STRENGTH AND ENDURANCE IN FOUR LEVELS OFSCHOOL-AGED BASEBALL PLAYERS

The purpose of this study was to compare strength and endurance differences in shoulder external and internal rotation torque ratios among four levels of school-aged baseball players, The subjects (N=97) were assessed the strength and endurance strength of shoulder internal and external rotation muscles with Kin Com dynamometer. The functional scapular plane of shoulder movement was used as the testing position, Strength development of IR and ER generally varied with school-aged increased, Comparing with adult pitchers, adolescence and pre-adolescence baseball pitchers had relatively weak shoulder external rotation muscles, especially after high repetition muscle contraction. In order to prevent shoulder injury in adolescence and pre-adolescence baseball throwers, muscle endurance in shoulder external rotators must be emphasized

SWITCHING THE HORIZONTAL GRF TO THE PATH OF PROGRESSION IN THE TABLE TENNIS FOREHAND DRIVE

Knowing the kinetic strategies of the lower limbs is a crucial factor to investigate the forehand drive which comprises the changes of the foot placement. It is difficult to directly evaluate the movement of feet with the data of ground reaction force (GRF) and impulse (GRI).This study tried to analyze table tennis forehand drives via the GRF and GRI data based upon the anatomical perspective. The motion and the GRF data were collected from eight right-handed Taiwanese elite table tennis players. The horizontal GRF data were transformed to a reference frame and then integrated with time to get the GRI. During the forehand drive shot, the participants performed a greater lateral impulse to cause the trunk rotation and decelerated their body from initial to mid-phase and then accelerated the body to perform a forehand drive shot

HOP llMlNG OF SPLlT STEP AND KINETICS ANALYSIS OF LOWER EXTREMITIES IN BADMINTON START FOOTWORK

The purpose of this study was to compare the split timing, and lower extremity kinetics of badminton players during push-off steps in six directions. Eight collegiate elite male badminton players received the random shot from an opponent in one of six directions. Result: Hop timing was 0.014-0.037 sec after the opponent struck the shuttlecock. The leg that was opposite the movement direction showed significantly greater tower extremity horizontal push-off force than the other leg did. Conclusion: The hop timing of split step simultaneous with the opponent striking the shuttlecock. The leg opposite the movement direction was the main push leg. When lower extremities exhibit the correct pushing direction and reach the peak push off force within 0.3 sec after the opponent strikes the shuttlecock, players should have more effective return in badminton

THE UPPER LIMB EMG ACTIVITY COMPARISON OF DIFFERENT TABLE TENNIS FOREHAND DRIVES

The purpose of this study was to combine dynamics and surface EMG methods to analyze the movements of table tennis forehand drives by Taiwan elite table tennis players performing straight and cross court forehand drives from topspin and backspin serves. The kinematical data were collected by 10 Vicon MX13+ high-speed cameras and one Biovision system was used to record the EMG signal of seven muscles groups on the dominate hand. The results showed that there were significant differences among the four table tennis drives. The players exerted greater muscular activity in the wrist extensors, the biceps and the triceps for the backspin serve forehand drive than when returning the topspin serve forehand drive, not only on the straight but also on the cross court strokes

BIOMECHANICAL ANALYSIS OF THE UPPER EXTREMITY IN THREE DIFFERENT BADMINTON OVERHEAD STROKES

The purpose of this study is going to analyze the biomechanical variables (net joint forces, moments and powers) on the upper extremities of the international elite badminton player when he was performing different (smash, clear and drop) overhead stroke movements. In this study, we are interested in analyzing from the phase of the period before and after the point of making contact with the shuttle. The 2D inverse dynamical solution was the method to calculate the net force, net moment and the power of the upper extremity around the contact. The results showed that dynamical pattern of the three overhead strokes were different. The player experienced eccentric contraction before or after the contact. The regular training on the wrist extensors will be necessary for reduce the risk of the injury of wrist extensors

CALIBRATION OF PRESSURE SENSORS FOR HAND GRIP MEASUREMENT

The purpose of this study was to assess the accuracy of grip force sensors. Methods: Several standard weights were used to calibrate the grip sensor in the static condition, The descriptive statistics and linear regression were used to present the accuracy and errors. Results: Results of this study showed a high level of sensing areas linear relationship under static loading. Conclusion: Data from this study showed high accuracy of the pressure sensor. The pressure sensor could te used for hand grip measurement

THE BIOMECHANICAL ANALYSIS OF THE TAEKWONDO FRONT-LEG AXE-KICK

The purpose of the study was to analyze the biomechanics of taekwondo front-leg axekick. One force plates, two synchronized high-speed cameras were used to measure biomechanical parameters in each phase of the front-leg axe-kick. The results included: 1. The average reaction time and movement time were 0.423 sand 0.327 s, which respectively occupied about 56% and 44% of attack time. 2. The maximum velocity of hip, knee and ankle were 1.74 m/s, 5.25 m/s and 7.43 m/s respectively. When the kicking leg touched the target, the velocity of knee and ankle were 0.78m/s, 1.72m1s, and 4.64m1s respectively. 3. The peak vertical GRF and impulse were 0.96 SW and 77.57N-s. For decreasing the movement time, it's suggested that an athlete should increase the power and flexibility of lower extremities during the training section

KINEMATIC ANALYSIS OF THREE DIFFERENT BADMINTON BACKHAND OVERHEAD STROKES

The purpose of this study was to analyze the performance of three different backhand overhead strokes (smash, clear and drop). In this study, we are interested in analyzing the phase of preparation position to the point of making contact with the shuttle. Two Redlake high-speed video cameras operating at 250Hz were simultaneously used to obtain 3-D data. A repeated one-way ANOVA and Pearson product moment correlation were used to test the selected variables at .05 significant levels. It was concluded that increasing the shoulder angle of drop and the wrist angular velocity of smash and clear will increase the shuttle velocity

DYNAMICAL EFFECTS OF SPRINT START ON DIFFERENT STARTING BLOCKS

The purpose of this study was to examine the dynamical variables of sprint start in two different starting blocks setups. The ReacTime Personal Systems was used to record the Reaction Time (RT) and the Power of 20 teenaged sprinters (15 males and 5 females) in the sprint start. In addition, the Newtest Powertimer photocells were used to collect subjects’ 0 to 10 metre (T10) performance after the sprint start. The variables were tested by the repeated measures one-way ANOVA by SPSS 19.0 statistical software at a .05 significant level. The results showed that there were better effects on the short starting block (SB) in power generation performance than the long starting block (LB). The athletes can apply short starting block and make adjustments and modifications based on their training conditions

BIOMECHANICAL ANALYSIS OF BADMINTON FOREHAND NET SHOTS

The purpose of this study was to compare the upper extremity kinematics variables of badminton forehand dab shot, stab shot and cross court net shot. The participants were eight elite collegiate male players in Taiwan. The kinematical data were collected by Vicon system (250Hz) and the Visual 3D software was used to analyze the variables. The results indicated that the elite badminton players perfomed dab net shot with less angular velocity in racket upper limb joints. They performed the stab net shot with faster angular velocity in forearm supination and wrist ulnar flexion. The cross court net shot had greatest angular velocity in shoulder internal rotation, forearm pronation and the least distance between the contact point and the mid-line of body