BIOMECHANICAL ANALYSIS OF TAEKWONDO ROUNDHOUSE KICK FOCUSED ON PHASE BEFORE TOE OFF

The purpose of this study was to clarify the biomechanical taekwondo roundhouse kick (RHK) mechanism of the lower half of the body in the phase before toe off the floor (READY phase) focusing especially on techniques for producing faster kicking speed and shortened time of kicking. The results were summarized as follows: i) motion of hip joint in support leg had relation to the flow of mechanical energy to pelvis, ii) extension of hip joint in support leg produced the translational velocity of pelvis, and iii) players accomplished motion of hip joint extension by providing the torque of hip joint extension in support leg at early time. Taken together, our data suggests that coaches should pay greater attention to support leg and READY phase in order to improve the players’ kicking technique for kicking fast and quick

TENNIS ONE-HANDED BACKHAND STROKE AT DIFFERENT IMPACT HEIGHTS

The purpose of this study was to compare the kinematic differences of the racket during a one-handed backhand stroke at different impact heights. Five male collegiate tennis players were instructed to stroke the incoming balls from different heights to a crosscourt target area. The impact heights were classified as High, Middle, and Low. Significant differences were observed at 3 heights for racket angles (p \u3c 0.05). The decrease of the angular velocity of upper trunk right-lateral rotation at High might be the main element that resulted in a decrease in the resultant velocity of the racket at impact. The greater moment of inertia of the dominant arm and racket about shoulder horizontal abduction-adduction axis at High made arm difficult to be accelerated. It might influence the velocity and control of the one-handed backhand stroke at high impact point

A BIOMECHANICAL ANALYSIS OF THE RELATIONSHIP BETWEEN TENNIS SERVICE MOTION AND BALL SPIN

The purpose of this study was to investigate the relationship between the service motion and the ball spin. Ten male university tennis players were participated in this study. Three-dimensional coordinates data of the players performing flat, kick and slice services were collected using an 10-camera Vicon MX system. In a similar way, the three-dimensional coordinates data of the reflective markers on the ball were collected. The ball spin is controlled by swing direction of the racquet without changing swing speed. When players put a spin on the ball, they changed swing direction rightward to avoid a head-on collision of the ball and racquet. Moreover, the swing direction was mainly controlled by not change of arm swing motion but change of upper body posture

BIOMECHANICAL ANALYSIS OF ROTATION STRATEGY OF BACKWARD SOMERSAULT IN ARTISTIC GYMNASTICS

The purpose of this study was to examine the rotation strategy used by gymnasts to successfully land after a backward somersault. Nine male university gymnasts (1.66 ± 0.03 m, 61.2 ± 0.75 kg) performed a backward-tucked somersault from a box (0.3 m height). Three-dimensional coordinate data was collected by a Vicon MX+ system. We compared the trials in which the landing succeeded and trials in which the landing failed. There was a difference in the moment of inertia during the airborne phase and the phase time. The results of this study suggest that changing the moment of inertia during the airborne phase has a significant effect on the body rotation. In particular, it is considered that the timing at which the phase is switched by changing the moment of inertia determined the body rotation

BIOMECHANICAL CASE STUDY ON TOSS UP MOTION IN TENNIS SERVE

The purpose of this case study was to suggest some coachings through the analysis of relationship between the ball toss and the whole body motion variability observed during the tennis serve. Comparing the standard deviation (SD) of impact location for each serve (flat serve, slice serve, and kick serve), in Y-axis direction (forward/backward), SD of flat serve was larger than slice and kick serve. To correspond such variability, subjects i) moved along the direction of variability, ii) did NOT adjust the trunk joint motion. The small angular motion of proximal segments, such as the trunk and upper arm, significantly affect the impact location. Therefore we encouraged players to use the translational motion of upper trunk to adjust the variability

ANALYSIS OF RELATIONSHIP BETWEEN HAMMER HEAD VELOCITY AND RADIUS OF CURVATURE

INTRODUCTION: In many research papers, the relationship between the hammer head velocity and the radius of curvature of hammer was discussed. The purpose of this study was to re-examine the relationship between the hammer head velocity and change in the radius of curvature with the 2-D computer simulation

LENGTH OF SERIAL ELASTIC ELEMENT AND CONTRACT ELEMENT DURING VERTICAL JUMP: COMPARISON OF STATIC OPTIMIZATION AND DYNAMIC OPTIMIZATION

The purpose of this study was to: (1) compare the length of serial elastic element, contract element estimated by two different optimizations, and (2) examine that whether those methods are able to evaluate the length of serial elastic element, contract element. One healthy male performed a vertical jump with the maximal effort from a squat position. The coordinate data and the ground reaction force were obtained with a 3D motion analysis system (250Hz) and force platform (10WHz). For a dynamic optimization, we developed muscle activation driven forward dynamics simulation model. As a result, the pattern of length of element estimated by the dynamic optimization was similar to the pattern reported by Kurokawa et al. (2001). On the other hand, the pattern of length of element estimated by the static optimization differed from the pattern reported by Kurokawa et al. (2001). This finding might be useful to clear the mechanics of human movements

A COMPARISON OF HAMSTRING MUSCULOTENDON DYNAMICS DURING HIGH-SPEED RUNNING BEFORE AND AFTER A FATIGUE EXERCISE

The purpose of this study was to compare the musculotendon dynamics of individual hamstring muscles between before and after a soccer-specific fatigue exercise during the late swing phase of high-speed running. Eight male soccer players performed three sprintings before and after the fatigue exercise. Whole-body kinematic data and ground reaction forces of the support leg were recorded using a three-dimensional motion analysis system and force platform. A three-dimensional musculoskeletal model with 43 Hill-type musculotendon models was used to estimate the musculotendon dynamics. The results of this study showed that there were no significant differences in the peak values of musculotendon force, power, length, and elongation velocity in the hamstring muscles before and after the fatigue exercise

KINEMATIC STUDY ON SEOI-NAGE, TECHNIQUE COMPARISON OF PLAYERS WITH OR WITHOUT ELBOW JOINT INJURIES

The purpose of this study is to clarify how to apply Seoi-nage to reduce the occurrence of injuries in elbow joints. Five participators were male college judo athletes, one as the Uke (receiver) and other four as Tori(Thrower), two of them with pain in elbow and other two without pain. The result shows that the players without pain in elbow flexed the elbow joints greatly and lifts the Uke by not bend the hip joint too much. Two considerations about the players(Tori) with pain in elbow. 1) The movement of Nagekomi in elbow joints was different from the Uchikomi. Therefore, it assumed that great load put on his elbow joints. 2) Hip joint bends after contacting with Uke and the upper body bends and throw with the power of the arm. In conclusion, the player who uses less strength of the lower extremities instead of the strength of upper body, which might cause injury

KINEMATIC ANALYSIS OF SOCCER INSIDE KICK MOTION FOR STATIONARY BALL AND PROJECTED BALL

The purpose of this study was to analyse the inside kick motion kinematically under the mimic situation of a soccer game, by comparing the motion of kicking the stationary ball on the ground with the motion of kicking the ball projected from the launcher machine. Five male university soccer players conducted inside kicks under the two conditions of the stationary ball and the projected ball. The kicking motion were collected with an optical motion capture system. From the results of this study, the following were suggested as a motion to kick a projected ball. 1) Adjustment of hip joint adduction-abduction and knee flexion-extension were important so as to correspond the swing trajectory to the ball. 2) It is important to kick an upper part of ball