Kinematic Analysis On The Two-handed Backhands Stroke Skills Of The World-famous Male Tennis Players

In tennis, the backhand stroke remains one of the most commonly-seen skills, especially in the base line standoff. In the base line struggle, each player will return the ball towards the other's dead zone because most players' forehand outweigh their backhand and backhand zone becomes the target during the attack, thus two-handed backhands fit in.Through three-dimensional photography and mathematical statics method, this dissertation makes a kinematic analysis of the four well-known two-handed players who took part in the China Open 2014, namely, Novak Djokovic,Rafael Nadal, Murray and Marin Cilic. Meanwhile, this dissertation figures out common skills they four share, displaying kinematic characteristics of the four's two-handed strokes and helping to set a model to the principle in line with the sports biomechanics in order to provide references for the coaches and athletes and enrich the tennis skills theories.After a careful test of the four athletes' backhands stroke, a kinematic conclusion is made as follows:During the backswing stage, a huge angle between the knee and hip joints of the four athletes is observed, with a higher centre of gravity. When the backswing is going to finish, a maximum left elbow joint angle is reached, which shows that the arm has extended to a considerable extent. Moreover,Nadal is observed with a huger shoulder joint angle than the other three. When the four athletes are finishing their swings, they keep a high wrist linear velocity and racketing: Djokovic's left wrist linear velocity is1.94 m/s and his right 1.75 m/s and the racketing reaches 4.44m/s;Nadal's left wrist linear velocity is 1.73 m/s and the right 1.90 m/s and his racketing hits 4.09 m/s;Murray's left wrist linear velocity is 2.63 m/s and his right 2.13 m/s and the racketing reaches 5.57m/s; Cilic's wrist linear velocity is 2.66 m/s and his right 1.95 m/s and the racketing reaches 5.59m/s.During their swings, it can be observed from the hip and knee joints, the center of gravity of athletes are rising gradually, indicating that pedal strength of lower limbs are utilized. We have found that shoulder joints' angles of Djokovic and Nadal surpass those of Murray and Cilic, which means Djokovic and Nadal hit the ball in such a distance that they can easily extend themselves.The twist angles of Djokovic,Nadal, Murray and Cilic reach 54.1°, 43.1°,52.8° and 33.7°respectively, which meansCilic's twist angles ranks the first. When he is serving the ball, all his body joints are moving in an increasing speed and reach the maximum when the ball hits the racket.In the follow through phase, the shoulder joints of all four athletes are increasing when they hit the balls, especially the left shoulder joint, which means their elbows are raised to some extent. Their elbow angles are decreasing, indicating that obvious movements occur during their the follow through and time to hit the ball is shortened; the twist angles of Djokovic, Nadal, Murray and Cilic are 63.4°,60.7°,66.6°and 54.7°, all of whom move to a considerable extent that it conforms to the principle of large range and long distance.