1. Judging from the hitting direction of the racket when it touches the ball. From the moment the racket touches the ball, the racket face leans backward and has downward or lateral movement, that is, downward rotation or lateral downward rotation. Because the backspin rubs the middle and lower part of the ball, the shape is flat and inclined. Even if there is a fake action, because you have to hold the ball and rotate it, the wrist action is relatively large. Even if there is a fake action, there will be a slight pause in hitting. The opposite is topspin.
2. Judging from the running speed after releasing the ball. After the topspin touches the table, the speed of the ball will suddenly increase due to rotation. The topspin serves quickly and suddenly. It is also because there is no short ball, the arc is slightly higher, and the running speed is slower and more stable.
3. Judging from the swing. Wipe the ball from the front of the racket from the left back side to the right side of the ball, that is, the ball is spinning down, and rubbing it to the right side is spinning up. In the use of the racket, the ball is rubbed from the right back to the left front to the lower part as a reverse backspin and the left front as a reverse topspin.
4. Judge according to the type of racket served by the opponent. When the opponent serves, at the moment of touching the ball, the racket face leans back and has downward or lateral movement, which is downward rotation or lateral downward rotation; If the opponent serves with a backhand, and the direction of force is upward or forward, it can be judged as topspin or non-topspin. The strength of rotation is mainly judged by the power at the moment of hitting the ball and the angle of the racket face. The greater the downward force, the more backward the racket face, and the greater the downward rotation force, and vice versa.
Another simple method is to judge the rotation direction of the ball by the arc of the incoming ball. Generally speaking, the backspin runs fast, the arc is low after landing (the second jump), the forward force is weak and the sinking is fast; On the other hand, topspin or non-topspin serves mainly upward, so the ball runs slowly and has a high arc after landing, and the forward momentum of the ball is greater than that of backspin. At the same time, it can be judged whether the ball rotates to the left or to the right according to the lateral rotation direction of the service after landing.