- Go for a light 15 minute job before playing.
Do this stuff during the time that would normally be sit down water breaks:
- Get a jump rope and skip rope every 20 minutes of hitting for about 2 or 3 minutes straight.
- Do some push ups during water breaks.
- Run lines (run forward to the net along the sideline.... run backwards to service line... side shuffle to center service line... straight up to net... etc.).
- Run at a higher than moderate pace around the court. 2 laps.
If you're not 4.5 or so, it's hard to get a really good cardio workout from tennis. Beginners and even intermediates spend most of their time walking around picking up balls or standing in place hitting back and forth.
So what you need to do, if you're not regularly getting into grueling 12 to 15 ball rallies with your opponent, is to supplement the exercise you get from hitting by doing high intensity stuff (like jumping rope) during breaks. So no more sit down breaks. Take a sip and use that break time to run lines, skip rope, do push ups, etc.
Punishing your quads/thighs is the best way to go about turning your court time into a fat burning workout. It's the biggest muscle in your body and working it means you'll burn more calories and fat, even hours after you're done working out.