You're pedaling hard through the Chinese countryside, past red pagodas and pink flowering trees that sway in the breeze. Your heart's pumping, and you can almost feel the calories burning away. But there's trouble ahead. A serpentine green animal slithers into view. It has a large mouth, a long tail—and wings. Fortunately, the S3 is built to handle dragons. You just shoot them down by squeezing the triggers on the handlebars.

Obviously, the supernatural chase is unfolding in a videogame. But what might be surprising is where it's being played.

The S3 was created by Expresso Fitness, a Sunnyvale, California-based startup that's among several pioneering a new kind of exercise experience—some call it "exertainment"—for the videogame generation. The Web-connected recumbent exercise cycle, with a 19-inch L.C.D. screen, hit health clubs across the U.S., from Crunch to Gold's Gym, this fall.

"Games have been around for 25 years," says Expresso C.E.O. Brian Button, "and it's amazing that people haven't used them for more active entertainment before."

Gyms, health facilities, and even schools have been adopting existing videogames for their exercise regimes. The dance-pad videogame Dance Dance Revolution was among the first to get gamers sweating. The EyeToy, the motion-tracking camera for Sony's Playstation 3, has been used for aerobics in games such as EyeToy Kinetic. In May, Nintendo introduced the Wii Fit—a wireless balance board used for yoga and pilates and even snowboarding—to wide acclaim and sales. According to NPD Group, a technology research firm, the Wii Fit sold 1.1 million units in its first two months alone.

"What's so interesting about Wii Fit and other games that encourage people to get moving is that they have grown legs of their own," says Marc Franklin, a spokesperson for Nintendo of America. "We have seen gyms, schools, hospitals, physical rehabilitation centers, and other facilities incorporate these games into their programs without any encouragement from us."

Keith Worts, chief operating officer of Crunch, which has 30 gyms nationwide, has introduced the Expresso bikes at some of his facilities and is now looking at bringing Wii Fit titles into the gyms too. The hope is to draw new members who don't ordinarily like to exercise. "These new technologies and initiatives are innovative and can help take your mind off the fact that you're exercising, which can be a painful thing."

A Grass Valley, California, startup called GameRunner has invented a novel way of navigating first-person shooter games like Halo with a treadmill. Its First Person GameRunner is a manually powered treadmill that plugs into a PC's USB port. As a player walks, the treadmill measures the motions optically and translates them into corresponding movements within the virtual action. A set of handlebars are used for steering, with trigger buttons for firing and other in-game actions. The GameRunner is coming in the first quarter of 2009 for $495, but Olympic gold medalist swimmer Erik Vendt already owns a prototype.

Another product, Gamercize, lets players plug a power-stepper into any videogame console, including Microsoft's Xbox 360, Sony's Playstation 3, and Nintendo's Wii, so that moving in a game is a matter of pumping your feet rather than flicking your thumbs.

"The Wii has had a huge impact," says Terry Grim, co-founder of Grass Valley, California–based KickStart Fitness, which makes the product. "People are starting to realize that playing videogames doesn't mean sitting on your rear end anymore."

Rosemary Lavery, spokesperson for the International Health, Racquet & Sportsclub Association, a trade group that represents more than 9,000 clubs and suppliers in 78 countries, says exertainment is not just a way to help consumers stay in shape, but a means to give gyms a contemporary makeover.

"It makes working out more of a modern experience," she says. "Games get new people in—the generation who grew up with technology and are used to using it in everything they do."

And there's good news for those working out on the Wii at home. In July, the American Council on Exercise announced the findings of a report on the Nintendo Wii by the University of Wisconsin's La Crosse Exercise and Health Program. The study found that gamers burned up to 216 calories per half hour in games such as Wii Tennis and Boxing.

But while the titles increased heart rate and oxygen intake during gameplay, they fell short of the real thing, concluded Cedric Bryant, Ph.D., chief science officer of A.C.E. "While they have managed to get traditional gamers off the couch and our results show that Wii Sports offer more of a cardio benefit than sedentary games, we believe there is no substitute for the real sport," he said. Oh well, back to the gym.