Originally Posted by JackB1
Definition: The Target Plane is the plane that includes the tennis ball at contact and the imaginary target inside of the deuce or ad tennis court. This plane should be parallel to the perpendicular to the racquet string bed during the impact. The Target Plane basically determines the boll velocity direction. We shouldnít change amount of the arm pronation, because it is almost impossible to control, in order to change bollís direction. Itís much easier to alter direction of the Target Plane. Always keep the range of the arm pronation around 90į.
Letís analyze Stosur and your arm actions before contact.
In pic.1 Stosur longitude axis of the racquet is parallel to Target Plane. In pic.3 longitude axis is perpendicular to the Target plane. She rotates her racquet by using internal shoulder rotation (ISR) around 90į.
In pic.4 longitude axis of your racquet is already perpendicular to Target Plane. Thus you cannot use, before contact, internal shoulder rotation at all. Thatís why you apply ISR after contact, but that doesnít make any sense. With this technique you never are going to get powerful and consistent serve.