Try the Jimmy Conners method for a pulse pounding workout.
Tennis is an anaerobic sport.
That is, it is played in short bursts of normally four to ten seconds and requires a special kind of conditioning. Some players condition themselves by running long distances each day, but that has only limited value for playing tennis. The muscles and lungs trained in long distance running respond well to a consistent rhythm, while tennis often demands a sudden violent and inconsistent need for oxygen and muscle contractions. I will attempt to show you that it the answer lies in your genetic make-up and the nature of your practice. Having been involved in professional tennis for four decades, I have seen players who need four to five hours a day of hard practice before they feel ready to take on the world.