| Introduction:The serve, a closed skill in which the player has full control, is the most important stroke in tennis. However, it is also a difficult stroke to master. Not only do the arms prescribe different movement patterns and rhythms, but they must coordinate with the movement of the lower limbs and the trunk. Because of its importance and complexity, tennis serve becomes a closely watched issue. Since there are few studies on tennis serve of the national team players,8 Chinese national tennis team players have been taken as the subject in this research. This study was undertaken to provide both the player and coach with a better understanding of the mechanical basis of the serve.Methods:The 8 players were filmed using a two-camera, three-dimensional direct linear transformation set-up. Two high-speed cameras were placed around the baseline and used to record the calibration frame, which was necessary for calculating three-dimensional coordinate data using the direct linear transformation (DLT) method. The players performed three "flat" serves from the right service court, while serving motion was recorded by the two cameras operating at 200 Hz. According to the estimates by a coach of Chinese national tennis team, the best serve was selected for analysis. Data were processed by Shi Xun Analysis System of Beijing Sport University.Results:The ball got an upward initial velocity of 6.15 m/s,0.34 m/s in the fore-and-aft direction and 0.23 m/s in the right-to-left direction on average when it was tossed. The ball was hit at a mean distance of 1.10m below a peak ball toss height of 3.67m. In backswing, the front knee flexion angle was 91.35°and the back one was 104.64°on the average. The lowest point of racket head was about 20 cm lower than the height of the body center of gravity when the player's back scratch was over. The mean velocity of the ball was 42.64 m/s after impact and the average height of the impact point was 2.57m which was 1.52 times the height of the body. The time sequence that the maximum angular velocity of each joint appeared was:hip, knee, ankle, trunk, shoulder, elbow, wrist. Discussion/Conclusion:1. The Chinese national tennis team players tossed steadily because the ball moved little in the right-to-left direction. However, the mean peak ball toss height was a bit higher, which might affect the accuracy of the stroke.2. The FU technique leads a larger trunk rotation than the FB one. Choose one according to the player's individual condition.3. At the end of backswing, some players shifted their hips sideways a lot towards the net. This position was unbalanced and went against pushing off the ground. Make sure the center of gravity between the legs at this moment.4. "Back scratch" depends on a good thrust of the legs, so taking more exercises to develop the power of legs is necessary for tennis players.5. Since forwardswing starts with the stretching coxa, and trunk is the transportation hub of movement chain. Suggest take more core muscle training, such as abdominal muscle exercises and abdominal oblique exercises.
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