Kinematics Analysis Of Side Topspin Serve Technique Of Tennis Balls With Different Landing Points

Kick serve is mainly used in the second serve,but some scholars also point out that it can be used in the first serve.Tennis service should be combined with the rotation and location,a single serve based on power can not have a greater impact on the opponent,the players serve tactical purpose and intention should be set strength,speed,rotation and landing point in one.The aim of this paper is to analyze the kinematics of the technical movement of tennis kick serve at different drop points(Internal Angle,Body pursuit and External Angle),so as to provide theoretical basis and training reference for the technical movement of tennis kick serve.Two three-dimensional high-speed cameras were used to film the kick serve technique movements of 8 tennis players.The training period was 10±1.3 years,and the shooting frequency was 200Hz.The video analysis system of Beijing sport university was used to obtain relevant kinematics data of the collected serve technical actions,and digital filtering(Fc=10)was used to smooth and normalize the original data.Research findings and recommendations:(1)Ball throwing and racquet guiding stage:the relevant indexes of ball throwing at different drop points show significant differences,and the angular velocity of the shoulder joint of the left arm,the elbow joint of the right arm and the knee joint of the lower limb are significantly correlated.There is no significant difference in the way of standing at different drop points when serving.In order to improve the service concealment and avoid the receiver to predict the starting point and type of the ball in advance,it is suggested that a series of preparatory actions should be consistent before throwing the ball.(2)The "scratch back" phase:different placement side topspin serve technology"scratch" phase Angle of each link in the variable size with the exterior Angle-body-an internal Angle,in turn,increases,muscle stretching order as to upper limbs,lower limbs from proximal to distal to the service according to the placement of the differences between the reasonable control of each joint Angle variation,and make hair order coordinated force,bottom-up gradually transfer power to the shot.(3)Swing hitting stage:the striking speed difference between different landing points at the time of hitting is significant,which is reflected in the Angle from the outside to the inside:side spin outside>side spin behind>side spin inside;Topspin out<topspin back<topspin in.The hitting Angle of the inside corner is greater than that of the outside corner,and the serving Angle of the outside corner is smaller than that of the chase body and the inside corner.The multiples of the height of the hitting point and the height of the chase body are the outside Angle(1.69),the chase body(1.73)and the inside Angle(1.63).(4)Follow through stage:follow through stage controls the range of motion of the center of gravity.In order to reduce the risk of injury to the shoulder joint,it is suggested to coordinate the contraction of the trunk and upper limbs.After landing,keep the knee Angle in a reasonable range to be fully prepared for the next shot.