Turn your living room into the Tour de France

Americans own more than 50 million treadmills, Stairmasters, stationary bikes, and other home gym equipment. Let's be honest: Many have become little more than expensive laundry racks.

But that could change with new technology that connects them to the Internet, allowing people to compete with others from their dens. In some cases, whole new sports are being created with what were once viewed as merely fitness devices.

In the basement of his home here, Paul Flack logs onto a PC positioned next to his Concept 2 rowing machine. He has scheduled a race time using a $99 software package called RowPro (available at digitalrowing.com). Two other rowers - one from Vermont, one from Europe, strangers both - sign on for a 3,500-meter race.

Mr. Flack climbs into his rowing machine and grips the handle. A computer monitor shows three boats on a horizontal river. The race begins, and the muscular 49-year-old rears back and thrusts with his long legs. Off goes his virtual boat, the digital oars following the motion of his strokes. Not far behind are his two competitors. As trees on the riverbank roll past, the program constantly updates paces, distances, and times. It even shows Flack's heart rate.

"It's something fun," says Flack, who in the summer rows on the nearby Charles River. "[Working out] can get very boring, so you get some interaction."

FitCentric (fitcentric.com), a California firm, has sold Web racing software for stationary bikes, treadmills, and other machines as well. Their NetAthlon software uses video-game technology to re-create such real-world courses as Olympic venues and Boston's Head of the Charles. Hooked up to a big-screen TV, you can sense everything but the wind in your hair. In the coming weeks, the company plans to release a new system that will retrofit any piece of fitness equipment, bringing the technology to a much wider audience. It will retail for $169.95.

"There's a huge number of people who've bought fitness equipment who have grown bored to tears with it," says FitCentric's cofounder Ken Burres. "All of these things become really a lot of fun when you hook them up to a computer."

In today's "bowling alone" culture, is there a danger that this technology could eventually disrupt the positive social experience of joining teams and playing sports in the real world?

"I'm not overly concerned about it," says Peter Roby, the director of the Center for Sport in Society at Northeastern University in Boston. "If it were to really catch on, it would be a good thing in terms of encouraging people to participate in physical activity." In particular, he adds, more sedentary kids who are hooked on video games might be attracted to fitness.

Mr. Burres agrees, saying that his software may offer "virtual athletics," but it involves "real sweat."

Meanwhile, Web racing is proving to be a community-building experience just like regular sports. A couple of dozen online rowers, including Paul Flack, are planning to bring their equipment to the sidelines of this year's Boston Marathon. Together they will row a marathon together and cheer on the runners as they go past.