In fact, it has been shown that every pound of body weight you put on, actually puts 4x the pressure on your joints like the knees.
Here is a great site called Fitness for Tennis that can benefit anyone's game (from beginners to pro).
It is unlike P90X or any other workout system because it is designed specifically for tennis players, by professional tennis players and fitness coaches.
Get some free helpful tips, useful articles and also some free videos. Try the full 5 video set for the full 60 day program. Best of all, it comes with a full 365-day money back guarantee. They also guarantee on the site that if you do not gain 1 NTRP, they will allow you to return the product for a full refund. Simply return it for a full refund if you're not satisfied.
Hint: Now at the top of the page, get $10 off the program with their special discount.
As some of the top pro's over the past year like Novak Djokovic and Mardy Fish have demonstrated; when your fitness gets better, usually so does your tennis ranking.
Better health. Quicker footwork. Stronger tennis.