You love the workout you get on the treadmill and elliptical. Best cardio equipment going, you say.

But have you considered rowing? "It's a great workout," Charles Anderson said. "It literally works every major muscle group."

Anderson and his wife, Aubrey, recently opened Rowbot Fitness, an indoor rowing club in Smyrna, Ga., that fitness experts say is part of a growing nationwide trend in group exercise.

Although some fitness clubs have offered rowing machines for a while, they're hardly the main attraction.

Although he uses rowers in most of his clients' workouts, Brooks Conway, a trainer at Quest Gym in Duluth, Ga., said that the gym sells more rowers (at $925 a pop) than it uses.

Ideal for weight loss

Still, Conway said, interest in indoor rowing "is definitely growing" and almost all of his clients, especially those interested in losing weight, use one of Quest Gym's two machines in their workouts.

At Rowbot Fitness, which opened last month, rowing is the only exercise going.

The hourlong classes, held most days of the week, take students through speed and distances drills on indoor rowers, called ergs.

"It's a pretty small industry, with only about 50 in the country," said Charles Anderson, a senior software engineer. "Five years ago there weren't nearly that many, but it's picking up steam." Rowing reclaimed Anderson's attention in 2008 after he put on nearly 60 pounds.

"I wasn't exercising anymore and spent a lot of time in front of the computer and TV, neither of which did much for my waistline," he said. "I went from 190 to over 250 pounds over five years." A former Georgia Tech rower, the 29-year-old Anderson said he knew the benefits of the sport and the vast amount of calories -- more than 750 per hour -- he could burn doing it. He lost the extra pounds in eight months.

Then in 2009, while attending the Atlanta Erg Sprints at his alma mater, Anderson said he met Lowell Caylor, owner of Greenville Indoor Rowing in South Carolina.

"That was the spark for starting my own business," he said, and the Andersons launched Rowbot Fitness on July 23.

Chris Jordan said he found out about the gym while perusing Facebook.

"I'd never heard of a rowing gym, but I'm always looking for different workouts to try and decided, 'Why not?' " said the 26-year-old Smyrna resident.

"I love it," Jordan said. "Each workout is different. Some are quick sprinting like we did today. Some are longer distance, less intensity." During the recent workout, Jordan and half a dozen others went through an hour of sprints with Aubrey, straddling a machine in the middle, setting the pace.

"Put a lot of power behind those strokes," she said as the machines whirred and "Invincible" by OK Go played in the background. "Two more. One. Two." They rested for three minutes, took a drink of water and repeated.

Overall exercise

Charles Anderson said every time you take a stroke -- an estimated 26 per minute for an hour -- you use the leg, core and arm muscles, but the perceived rate of exertion is low because you're using all your muscles as opposed to a select few.

In addition to its health benefits, he said, indoor rowing is appealing because it's easy for even newcomers to pick up and enjoy. And "it's something that people will stick with," he said.

That has been the case so far for Lisa Adebiyi, who has been coming to the club since opening day.

Adebiyi, 29, said she's always looking for different workouts because variety is her key to keeping weight off. Indoor rowing, she said, "is very different from anything else I've ever done." As Adebiyi left Rowbot Fitness last week, another club regular, Adair Flowers, was arriving with her husband and 11-year-old son in tow.

"I was excited to find something low-impact [and] easy on the body," she said, "but that still gives me a good workout."