IT WAS A PLEASANT SPRING afternoon, and I was rolling along a county lane on my new Rowbike, when four racy-looking roadies pulled up. "Hey, guys!" I said, trying to act casual while jackknifing furiously to maintain pace. "Sweet rides. Titanium?" They accelerated as a flock, casting back curious glances. As soon as they disappeared, I hit the hand brakes and doubled over, heaving.

Best described as a rowing machine, recumbent bike, and Marquis de Sade–worthy fitness toy rolled into one, the Rowbike requires you to push with your legs (the seat slides on a rail) while you yank on a large swingarm that pulls a chain attached to your rear wheel. The madcap contraption is the brainchild of ScottyO, né Scott Olson, a Minnesota-based inventor who, in 1979, bolted a row of roller-skate wheels to his hockey boots and dubbed them Roller-blades. In 1993, he was working out on a Concept2 indoor rower when he dreamed up his second act.

"I was cranking on the C2 in a gym, bored out of my gourd," he says. "I thought, There's got to be a way to get this thing on wheels."

I could sympathize. I've had an on-again, off-again relationship with the C2 myself over the years. Fact is, the C2 is an efficient tool that's become a fixture in more than 7,000 gyms and boathouses around the country. I've always appreciated rowing, since it hones arms, back, shoulders, and legs in a way that my typical training diet of running, cycling, and lying on the couch watching the Fox Soccer Channel just can't. I had even joined C2's burgeoning 151,000 member online community earlier this year so I could track overall results. Before long I'd recorded my best 2,000-meter time: 8:07.2, good enough to place second in New Mexico for my size and age. Of course, there were only two people ranked in my state. Where did I rate in my class worldwide? Number 4,954 out of 6,250.

I wanted to improve, but, like ScottyO, I could tolerate only so much suffering on an indoor stationary trainer. Searching for motivation, I rounded up a Rowbike. The gadget has been around for over a decade, but it's been lifted from complete obscurity to relative obscurity only recently, thanks in part to the 2006 addition of a chain-tensioning device that improved its efficiency by about 20 percent. The number of Rowbikers increased by around 1,000 last year, to some 6,000.

I brought the Rowbike to a local mall for its maiden voyage. One caveat: You'll want to be in a wide-open space when you first try this thing; there is a learning curve (read: sudden hard-to-control swerves) that you should not attempt to overcome on a busy road. After about 30 minutes, I began making laps on the half-mile service lane ringing the mall. Hills were tough, but my model, the 40-pound, $1,075 720 Crew, came with seven gears that allowed me to inchworm up modest inclines. Pretty soon, I was flying along the flats at 20 miles per hour and attracting a crowd.

After a week, I could feel my endurance improving. More surprisingly, I was having a blast on the Rowbike, despite being ridiculed by friends. I was even beginning to buy into some of ScottyO's unbridled optimism. "I'm sure the Rowbike is going to take off," he told me. "It could be as big as the C2."

Out on the road one evening, I encountered a woman on a sleek carbon-fiber Trek. No doubt she'd be full of questions about my wild ride, and I straightened up into my best rower's posture, preparing to field her queries. As she rolled by, she burst out laughing. Poor lass, I thought as she faded into the horizon. She had no idea what she was missing.