The direction you swing and pronate when you make contact with the tennis ball is another element / factor that separates the kick serve from the flat serve. When you hit a flat serve, you’re trying to swing through the ball – you want to “slap it,” or hit it clean. On a kick serve, now what you’re trying to do is swing up and across the tennis ball. That means you have to swing in a different direction. By swinging up and across the back of the tennis ball, you’ll put spin on it. That will pull the ball into the service box and cause it to “bounce funny,” or kick to the side.
In the video we compare the direction you swing when you hit a flat and a kick serve. We have Frank split screened. The serve to the left is Frank’s kick and the one to the right is the flat. First, let’s watch his flat serve. When he winds up and swings his arm is moving into the court. However, on the kick serve, when he swings his arm and the racket are moving across the tennis ball. When we play these clips together it should be clear that his arm is moving in a different direction on his kick serve than it is on his flat serve. He’s swinging more across the tennis ball.
Let’s look at Frank’s contact points because this next point is critical. The directions his tennis racket strings are facing when he hits the ball are more or less the same. The strings are facing the direction he wants to hit the tennis ball. Even though he’s swinging in different directions his strings are facing where he wants the tennis ball to go. This is key.
I’m going to take a moment to expand upon this last point because it’s really, really important. You want your strings to be facing the same direction when you hit the tennis ball regardless of which serve you are hitting. However, your arm is moving in a different direction on a kick serve than it is on a flat serve. That means you have to time your pronation differently on a kick serve so that your strings are facing the right direction at contact. In the video I show how this works. If I am trying to get my palm to face the camera, the timing of my pronation is different when I swing to my side versus straight at the camera. That same concept applies to a kick serve and a flat serve. You have to time your pronation so that your strings are facing the same direction at contact regardless of what direction your arm is moving prior to hitting the tennis ball.
Finally, let’s compare Oliver’s kick serve and flat serve side by side. His kick serve is to the left and his flat serve to the right. We’ll use this split screen to see how the brushing action of the kick serve is different from the solid contact of a flat serve. On a flat serve, Oliver swings pretty much straight through the tennis ball and hits it square. On the kick serve, he swings up and across the tennis ball. He doesn’t hit the ball “cleanly” because he’s trying to put spin on the ball.
If we compare Oliver’s respective contact points, you’ll notice that his contact point on the kick serve is slightly lower than on a flat serve. Probably by several inches (but not more). The reason he lets the ball drop is because he has to be able to swing up on the ball to generate some topspin.