It's not your leisurely recreational court game.
Cardio Tennis, says pro Ann Pellow, is less about improving your backhand and more about raising your heart rate and building endurance.
You don't have to be Venus Williams or Roger Federer to enjoy it, says Pellow, who teaches Cardio Tennis.
"I welcome people who have never even played tennis before," says Pellow. "All you need is a racket."
Cardio Tennis combines traditional aspects of the game, such as hitting balls, with rapid-fire drills that elevate the core body temperature and improve overall fitness, says Pellow.
The workouts take various forms, but most feature short bursts of high-intensity exercise followed by periods of rest. A typical Cardio Tennis workout involves a warm-up period followed by up to 50 minutes of aerobic activity and finishes with a cool-down. Students hit shot after shot, but between tennis strokes they might zigzag around cones or do lateral shuffles.
"In a typical tennis lesson, the instructor would be doing a lot of talking," Pellow says. "This is more about getting people to move and run and get a good workout."
Pellow uses music to make her Cardio Tennis sessions more fun. Clients can swat balls to the tune of "Somewhere Over the Rainbow" or "Puttin' on the Ritz," she says. "I'm going to get more modern music in there."
According to the Tennis Industry Association, Cardio Tennis classes are being offered across the country. The workouts burn as many as 600 calories and consistently take the heart rate into the proper "aerobic training zone," the association says.
Pellow's students measure their pulse rates every 10 minutes or so to gauge how hard they are working.
"The focus is to get people to get into their optimal heart rate zone for 30 to 50 minutes," she says.
The tennis association says that Cardio Tennis players "naturally improve their game" because they repeat various shots many times during the course of a class.
But some tennis purists are not big fans.
"I'm all for cardio workouts and getting people out on the tennis court," says Doug Atkinson, a club tennis director. "But I'm not real crazy about running people ragged while trying to teach them tennis technique."
"I run workouts and drills, and I do them at a reasonably fast pace," says Atkinson. "But it's not manic, and it doesn't involve all kinds of exercises that have nothing to do with tennis."
Pellow says Cardio Tennis is ideal for people who enjoy group exercise or just want to try something new.
"I recommend it to anyone who wants to get a real workout, or is tired of doing the same old thing," she says. "Just about everyone can do this."