By LINDA BAKER

The four stationary bikes look almost like any others, except that they are fitted with an arm crank and are hooked up to a generator. As riders pedal and turn the lever, the movement creates a current that flows to a battery pack. They generate an average of 200 watts, enough to run the stereo, a 94-centimeter L.C.D. television and a laptop for an hour at the Green Microgym in Portland, Oregon.
Adam Boesel, a personal trainer, wants his clients to burn calories, not fossil fuels. In August he opened the gym, one of a new breed of fitness clubs that seek to harness the power of human exercise as a source of electricity.
“It’s cool, fun stuff and an excellent workout,” said Mr. Boesel, who spent a recent morning demonstrating the power-producing bike machine, designed by a Texas manufacturer and called the Team Dynamo.
Mr. Boesel, 37, says the Microgym - the name alludes to the city’s signature microbreweries - is more than a gimmick. “It is an example of what a community can do to conserve energy .”
The club has energy efficient treadmills, remanufactured elliptical trainers and barbells “rescued from negligent owners on Craigslist,” Mr. Boesel said. Wall-mounted solar panels, to be installed this fall, will generate about eight kilowatts of electricity, he said. The gym doesn’t have any showers or drinking fountains, and the club’s 70 members live within walking distance, “which is probably the greenest part of the gym,” Mr. Boesel said.
The idea to install power-generating machines came from a Hong Kong club, California Fitness, that opened last year with similar equipment. On the same day the Microgym opened, the Ridgefield Fitness Club in Ridgefield, Connecticut, installed yet another version of the technology from a company called the Green Revolution on 17 of the club’s stationary bicycles.
“There’s an undercurrent,” Mr. Boesel said. “In 20 years, all cardio equipment will probably have the capability of generating electricity.”
The typical health club uses a huge amount of energy and water, said John Kersh, a former director of international development for the International Health, Racquet & Sportsclub Association. But a growing number of conservation-conscious consumers are beginning to change that, he said. “It’s not just, ‘How do you get fit-’ ” Mr. Kersh said. “It’s, ‘How do you make your lifestyle healthier- How do you reduce your carbon footprint?’”
David Butcher, a Web manager in Los Gatos, California, is ahead of the game. For the last two years, Mr. Butcher has been riding a pedal-powered generator he created in his basement. He said his 45-minute exercise routine, available to interested viewers on YouTube, supplies power to his laptop computer, a Roomba robotic vacuum cleaner and compact fluorescent lighting.
“I’m in better shape than I’ve been in 20 years,” Mr. Butcher said. “I feel like a motor.”