Originally Posted by Brenda Mensah
I tried this but it only worked with an abbreviated motion on my swinging arm and a low ball toss. I also had to hold the handle of the racket way up close to the throat because otherwise I would just end up smacking the racket on the ground after hitting the ball.
I found that it was easy to hit topspin, like it's supposed to help illustrate, but it doesn't translate to my normal serve when standing up because of all the adjustments I mentioned due to being on my knees.
I don't think this excercise was effective in improving my serve.
Well that's exactly the reason for serving from the knees. Most recreational players have a forehand grip, therefore no use of wrist on the serve, and the forehand grip also makes them hit downwards. When serving from the knees you have to learn hitting up and using the wrist. When you do that there is no danger of hitting the ground with your racket.
Learning how to put spin on the serve has not much to do with serving from the knees. If you have trouble getting spin on the serve, then try to serve while lying on your back. No chance to serve WITHOUT spin from that position.