Another typical difference between the kick serve and the flat serve is the amount of upper body rotation you get during the preparation and racket drop. With the kick serve, your upper body tends to rotate a little bit further around than it would on a flat serve. The reason is that, later on in the serve, your arm moves in a different direction on a kick serve than it does on a flat serve. We won’t get into why it’s different in this video – we’ll do that in the next video – but if I was, for example, going to throw a tennis ball at the camera (like I do in the video // or picture) my shoulders shouldn’t have to turn as far as if I were throwing the ball to the side. In the latter case, now my shoulders need to rotate further around so my arm can move naturally to the side. This same concept applies to the difference between the kick serve and the flat serve.
In the video, we compare Frank’s kick serve and his flat serve to see how his shoulder turn differs during his preparation. Frank’s kick serve is on the left and his flat serve is on the right. In the trophy pose you can see his shoulder turn is greater on the kick serve. This difference remains the same later in the motion when Frank gets to the racket drop. In the video we put a line through Frank’s shoulders during the various stages of his preparation for both the flat and kick serves to demonstrate how his shoulder turn is a little bit greater on the kick serve.