A Biomechanical Comparative Study Of The Back-shoot Techniques Of Male College Student Tennis Players

The world's top players of using two-handed backhand technology are very common in tennis match,as of today,90%of the first 20 elite men players are using two-handed backhand technology in ATP,and 100%of the first 20 elite women players using two-handed backhand technology in WTA,but the technology action is different in the different cases,the position posture vary,some scholars thinks that stance position mainly include two categories:the closed and open stance,those need flexibility using in the game,in the professional player,those technologies have been widely using,such as djokovic closed stance backhand,sharapova half open backhand,and serena Williams open backhand are common in the game.In this paper,using 3 d imaging and 3 d load synchronous technology test the two-handed backhand technology of 12 secondary male tennis players that comes from Chengdu sport institute,requiring kinematics and dynamics parameters,it analyses the differences of two actions in the aspect of kinematics and dynamics,to explore characteristics and regularity of two hands backhand action.Through comparing two kinds of action,found that the following conclusions:Kinematics conclusions:The backswing stage,(1)The time of this stage about closed stance backhand is bigger than the open stance backhand,the data shows very significant difference.from the point of shoulder Angle,the player of left elbow of open stance backhand is closer to the trunk.From the view of elbow Angle,because at the end of the backswing,The left elbow Angle of backhand action are smaller than the right elbow,the left elbow Angle reaches the maximum about two kinds of player's backhand action at the moment.(2)The moment at the end of the backswing,the speed of left shoulder,elbow and wrist about two actions are greater than the right,the speed from shoulder,elbow and wrist to the racquet head are consecutively increasing,it showed that the left arm drives the right arm to carry on the back.(3)The moment at the end of the backswing,the left knee Angle on two kinds of player's backhand action is less than the right,the center of gravity is on the left leg,.The velocity of lower limb joints presents hip>knee>ankle.In stage of turning the shoulder to shot,(1)The time of this stage about open stance backhand is bigger than the closed stance backhand,and the data has no significant difference.by the moment of racket surface contacts with the ball and the moment of the end of the backswing contrast,the center of gravity about the closed stance backhand's athletes are bigger than the open stance backhand.(2)The moment of racket surface contacts with the ball,the athletes's open stance backhand point of hitting a ball are close to the body.(3)The athletes's wrist in the closed and open stance backhand actions are not fixed after stroking a ball,but the left wrist is gradually flexural,the right wrist is gradually stretching,and giving the ball more spin.(4)The velocity of shoulder in two kinds of action,elbow and wrist are to the maximum before the moment of racket surface contacts with the ball,it conform to the whip movement theory.(6)the athletes's shoulder hip angle of closed stance backhand are smaller than the athletes's open stance backhand,it shows that the athletes's open stance backhand is more use the rotation of the torso.In the finishing swing phase,The time of this stage about open stance backhand is bigger than the closed stance backhand,and the data has no significant difference.the tendency of left shoulder Angle about the two actions are gradually increasing,while the left elbow Angle is a decreasing trend,it has obvious to take action.Dynamic conclusion:(1)At moment of left foot touched the ground,through the force value contrast,found that the backward direction of F(X)force of the open stance backhand is bigger,increasing the likelihood of ankle joint varus.Through the F(Y)force comparison,found that athletes's left foot of the open stance backhand are to brake more positive.By F(Z)compared to find that athlete's open stance backhand are more pressure on the left foot in the vertical direction.(2)The moment at the end of the backswing,the F(X)force on left foot of the athletes's closed stance backhand is smaller than the open stance backhand,datas show very significant difference.It shows that the forward and backward directions on left foot about the open stance backhand are poor stability.By the contrast of F(Y)found that those datas show very significant difference,by the athlete's body posture at this time,the left direction force of the closed stance backhand is bigger,Through the contrast of F(Z)found that the vertical force values of the closed stance backhand are much smaller than the open stance backhand,data show very significant difference.The athletes are to use the open stance backhand at higher risk of left foot injury.(3)At the moment of the racquet surface contacts with the ball,By the contrast of F(X)found that the forward and backward directions on left foot about the open stance backhand are poor stability.By the contrast of F(Y)found that the force values on the left and right directions of athlete's left foot about the open stance backhand are larger than the closed stance backhand,in order to transfer the centre of gravity to the right leg,By the contrast of F(Z)found that the vertical force values of the closed stance backhand are much smaller than the open stance backhand,data show very significant difference,it can cause the foot damage more easily.