Cardio tennis, anyone?

George Conlin is hustling. With his white cap pulled down low, the tennis pro instructs his class in a booming voice: "OK! Now, jumping jacks to the net!"

Eleven participants stretched across two tennis courts at the Longfellow Club in Wayland, Mass., obediently lurch forward – sans rackets. Next come lunges, then crossovers, then trunk twists. And that's just the warm-up. Soon the class grabs their rackets and lunge for balls hit at them rapid-fire, two in a row, before lapping the courts, slowing down just enough to tiptoe through rope ladders lining the perimeter on the floor. In the background, "Born in the USA" and "Play That Funky Music" beat from a boombox.

This is "cardio tennis," a program launched nationwide last year to try to woo gym rats to local courts and give seasoned players a way to improve endurance and foot speed.

Cardio tennis is one of several efforts by the United States Tennis Association (USTA) and the Tennis Industry Association (TIA) to revitalize participation. Other efforts include renovating public courts, offering more free youth programs, and marketing tennis as a lifelong sport for mind and body. It may be paying off. Tennis has seen an uptick in equipment sales in the past two years, a positive trend for an industry where participation has slid 13 percent over the past two decades.

"For tennis [participation] ... to be approaching what it was in the '80s is pretty good," says Mike May, a spokesman for the Sporting Goods Manufacturing Association (SGMA). "There are more things tugging at our time now.... It's one thing to watch tennis on TV, but it's another thing to find the time to play tennis."

The growth of fitness clubs and the recent popularity of extreme sports is giving tennis a run for its money. It seems whacking a ball over a net doesn't fulfill the fantasy of rugged individuality quite the same as, say, plunging down a gnarled hillside on a mountain bike.

Nor does an hour on the court translate into working up a sweat for the average tennis player, who spends more time retrieving wayward tennis balls than facing off with an opponent. And for an American public convinced that obesity is an epidemic, burning calories is now the end-all of exercise. SGMA numbers bear this out: Over the past two decades, activities that emphasize a cardiovascular workout have soared. The number of people using treadmills, for example, is up 992 percent.

Where some in the tennis industry saw a crisis, Jim Baugh, president of the TIA, saw opportunity. Why not develop a program that focuses on staying in motion instead of winning points?

That approach wasn't embraced at first by those who prefer silent courts punctuated only by the thud of balls and the occasional grunt.

"You definitely have purists who want to keep things traditional," says Mr. Baugh. "That's true for any activity. But you've got the people who really see the light and see the numbers with fitness activities. We're not replacing tennis, we're adding to the game. It's good for everybody."

In other words, both beginners and advanced players can participate in the same class, get a good workout, and spend more time on the courts. It's a formula that is gaining broader acceptance.

Baugh says it took 2-1/2 years of planning before 600 clubs signed on to offer cardio tennis beginning in the fall of 2005. In one year, that number has doubled. (A list of cardio tennis classes can be found at www.cardiotennis.com.)

At the Longfellow Club, Vixen Peare says this is her third class and she's hooked. "People on my tennis team have been taking [the class] and they said, 'Take a shot at it.' " Ms. Peare, a Spanish teacher who has been playing tennis for nine years, had no trouble returning the pro's rapid-fire serves. (A Monitor reporter in the class who sent many balls to the ceiling decided that tennis lessons could be a good idea.)

"The key to a good cardio-tennis program is the pro [teaching the class]," says Lorie Gochenour, who organizes adult tennis programs at the Longfellow Club. "They have to be able to adapt to all levels in the class. The beginner should feel just as comfortable as the advanced player."

One of the biggest initial challenges was simply persuading people to try it, Ms. Gochenour says, but it wasn't long before the club had a class of regular attendees.

Persuading the average person to step onto a court is a chronic problem in tennis. Busier lives is one reason. The sport's lingering association with the social elites who introduced "lawn tennis" to the US in the late 1800s may be another.

But today, the professional game is full of up-from-humble-beginnings stars, which industry experts say is helping to move tennis beyond the country club. In fact, 70 percent of the estimated 18 million people who play tennis each year in the US play on public courts.

"Elitism is a misconception that is going away," says Kurt Kamperman, chief executive of community tennis for USTA. "Take a look at the champions of today – the Williams sisters, [Andre] Agassi, [James] Blake, [Lindsay] Davenport – none of them grew up going to country clubs. Tennis is one of the few sports that has a low-cost, no-cost access anywhere."

That is, if people remember to go play. Tennis, like many sports, largely remains something to watch on ESPN. In multitasking America (witness gyms full of people reading or watching TV as they work out) coordinating pickup matches isn't as simple as it used to be.

"People's lives are so busy," says Mr. Kamperman. "It's not like we bump into each other and say, 'Hey let's go play on Saturday.' Having available courts is great, but the way to get [people] into the game is to have programs."