Originally Posted by Chas Tennis
In a serve instructional video I would like to hear more about the stretch-shortening cycle. The 'kinetic chain' is more a sequence of steps where bigger-slower muscles stretch and move smaller and faster muscles. I don't get that from the 'momentum' discussion or much in the way of specific motions with checkpoints. If anyone can understand the final motion that leads to the high racket speed at impact please indicate the time on the video where it is explained. If I stop the swing motion with the racket in ball strike position at about 4:48, it's not the motion and body orientation used in real pro serves.
Greg, Have you taken videos of your serves from behind with your high speed video camera?
You should be able to compare your serve to ones like this and see the differences between 130 MPH serves and yours. There are other similar videos taken from behind.
At impact most pro serves have a straight arm that rotates extremely rapidly at the shoulder joint. The racket is also rising up rapidly and strikes the ball with an angle between the forearm and racket. This clearly shows in the videos taken from behind (and their thumbnails with ball impact). That picture is what you want for an initial assessment of your serve.
Before anyone tries new serving techniques, they should understand the Todd Ellenbecker video on the shoulder. Search TW Forum: Todd Ellenbecker video shoulder serve
Not entirely sure what you're getting at when talking about with the stretch shortening cycle. I'm guessing that you're using it to how the muscles generate fast speeds from the racquet head drop. Regardless, talking about this motion when trying to explain a serve is more likely to damage form, as it sounds like it will lead to tensing the arm.
The high racquet head speed on the serve only requires normal muscle movements and is due to the triple hinged pendulum movement of the arm, about the shoulder, elbow and wrist. The movement of the arm is a combination of a passive and active movement.
Passive movement: If you keep the arm loose and move it using only the leg, core and shoulder muscles from the dropped head position the arm will naturally unfold into the fast motion we use in the serve, due to the mechanics of a triple pendulum. http://twu.tennis-warehouse.com/lear...lependulum.php
Active movement: The muscles in the arm do add extra power, however think how slow an arm only serve is (try hitting a serve from a sitting position if you don't believe me). Their main function of the arm muscles is to control the movement of the racquet in relation to this arm movement. The muscles control the planes along which the pendulum will travel, which is why you can hit flat serves, kick serves and slice serves with what is, for the most part, the same swing.
How does this mean?
-The racquet head drop is important for power, as it is the start of the pendulum movement.
-Power comes from relaxed joints, if the joint can move, it will. This is due to the centrifugal force acting on it as the arm accelerates. This includes forearm pronation, which must occur if the correct racquet head drop position and contact point are used.
-As the arm will naturally amplify the speed, you don't have to worry about really focusing on different muscles. You should relax the arm so that it can swing freely and use the arm muscles to ensure that the arm moves correctly through the contact point.
-Most of the racquet head speed is generated by the movements which accelerate the triple pendulum, the leg drive and core rotation. These are the areas where controllable power is available.
Also, height isn't an excuse for lack of power. I am 5'7 and I have hit around 110mph on my biggest serves. 5'5 Olivier Rochus once hit a 136mph serve.