ANALYSIS OF THE SERVING MOTION OF MALE COLLEGE TENNIS PLAYERS IN A SIMULATED MATCHES

The purpose of this study was to analyse the serving motion of the nineteen male college tennis players in simulated matches, and to seek for critical points for the improvement in the techniques by comparing with that of the world-class players reported by Fleisig et al. (2003) and Michikami (2014). The variables used in this study were the ball speed, racket speed, angles and angular velocities of the upper and lower limbs. Ball speed and racket speed for the male college players were significantly lower than that of the world-class players. The peak angular velocities of the right shoulder internal rotation and the left knee extension were lower in the male college players than those of the world-class players. For the improvement in the ball speed in serve, the critical points identified would be large angular velocities of the shoulder internal rotation and the knee extension

ANALYSIS OF RUNNING MOTION IN THE STARTING PHASE OF MALE SKELETON ATHLETES AT INTERNATIONAL COMPETITIONS

The purpose of this research was to assess which kinematic factors were related to running speed in the starting phase for international-level skeleton athletes during races. The starting motion of 22 male athletes was recorded with four video cameras during competitions and their starting motion was analysed by a three-dimensional direct linear transformation method. The maximum angular velocity of the thigh increased from the 2nd to the 3rd step. The maximum hip extension angular velocity of the support leg gradually increased up until the 6th step while the maximum knee extension angular velocity remained constant throughout. It would appear that international-level male skeleton athletes employed an increase in thigh motion and quick hip and knee extension for the support leg to obtain a large running speed

A CASE STUDY OF THE GENERATION OF ANGULAR MOMENTUM AND ANGULAR VELOCITY IN SOMERSAULT BACKWARD STRETCHED WITH 2/1 AND 3/1 TWISTS PERFORMED BY A SINGLE VARSITY MALE GYMNAST

The purpose of this study was to compare the angular momentum and angular velocity in somersault backward stretched with different number of twists performed by a single varsity male gymnast. The 3D motion captured system (Qualisys, 250Hz) was used to collect kinematic data of a single varsity male gymnast A who performed the somersault backward stretched with a double (2/1) and a triple (3/1) twist. The angular momenta and angular velocities of the body segments and whole body were calculated by the Tang’s method. More than a half of the twist angular momentum of the whole body in both 2/1 and 3/1 twists was generated during the take-off phase, which indicated that the gymnast A was classified as a contact twist type. In case of the gymnast A there seemed no difference in angular momenta of 2/1 and 3/1 twists, although he generated the angular momentum of the twist earlier in 3/1 than 2/1. He controlled the number of twists by his body maneuver before landing. Since these findings were obtained from a single gymnast, we need to investigate twist techniques and angular momentum date of various gymnasts

THE STANDARD MOTION MODEL OF A BASKETBALL SET SHOT FOR TEACHING

The purpose of this study was to create a standard motion model of a basketball set shot. Twenty-one male collegiate basketball players participated in three-dimensional data collection session (Vicon MX+, 250Hz), and the method proposed by Ae, et al. (2007) was used to create a standard motion model. The set shot motion in the standard motion model started with the shoulder flexion and hip extension in the downward phase, followed by the sequential motions of the knee, ankle, shoulder, elbow and wrist joints in the upward phase. Immediately before the ball release, the elbow and wrist joints were abruptly extended. The motion variation in the wrist, elbow and shoulder joints just before the ball release were small, implying there must be some commonality in these joint motions

HOW FEMALE COLLAGIATE GYMNASTS GENERATE A DOUBLE TWIST IN THE BACKWARD STRETCHED SOMERSAULT

The purposes of this study were to describe how female gymnasts generate a double twist in the backward stretched somersault and to draw suggestions to improve twist techniques of female gymnasts by analysing female gymnasts twist motion three-dimensionally. Three varsity female gymnasts performed thebackward stretched somersault with a double twist several times and were motion-captured with a Vicon system (250 Hz). The angular velocities and angular momenta of the body segments and whole bodywere calculated, based on the Tang’s method. The female gymnasts of the contact-type twisted the trunk, especially the upper torso largely before the aerial-type onelaterallyflexed her trunk after the toe-off with her right arm swinging down.For female gymnasts who intend to gain larger twist angular momentum or increase it, it is recommended to quickly move the opposite arm and twist the upper torso toward the twist direction during the take-off phase