Morning coming earlier and earlier at the gym

ATLANTA, Georgia (CNN) -- Even at 5:30 in the morning, Marlene Mauk is wide awake and smiling as she walks through the door of the Buckhead Athletic Club in Atlanta, Georgia.

She happily brags that her 30-mile commute was a breeze because she avoided rush-hour traffic. "I find it much easier leaving my house at 4:50 and being here at 5:30," 40-year-old Mauk says. "I can get my workout in and go on with my day."

Richard Vidoli, also 40, left his house in the Atlanta suburb of Acworth at 5 a.m. and walked in the club minutes behind Mauk. "I can save a good 40 to 45 minutes on my commute if I come in early," he says.

Vidoli and Mauk are part of an emerging trend around the country: Commuters leaving their homes before dawn to avoid the stress of being stuck on clogged highways. Watch how workers fight traffic and the bulge »

The U.S. Census Bureau reports nearly 18 percent of American workers leave home between 5 and 6:30 in the morning. That's 3 million more people than reported early departures during the same hours in 2000 and 6 million more than in 1990.

Workout centers such as the Buckhead Athletic Club are benefiting from the change. Club General Manager Michael Howell says his customers pressed for earlier hours.

In January, he complied by opening the doors every weekday at 5:30 a.m. By October 1, he moved up the start time to 5 a.m. "It's incredible to see the amount of folks that are now joining or re-joining because our hours of operation have been modified," Howell says.

He admits it has been a challenge to find workers willing to start their day half an hour before the customers arrive, but he says it's vital to keep up with changing trends. "People are starting earlier; 9 to 5 doesn't exist any more," says Howell.

The 15 other area fitness clubs owned by Howell's employer are also opening their doors at a time when most people are still in bed.

Mauk admits there are days when she'd like to sleep in. "I definitely sacrifice sleep," she says. "I only get about five hours of sleep each night, and I don't see my husband that much."

She's motivated to get up and get going in order to avoid sitting in stop-and-go traffic for an hour. "Doing something like this gets all the stress out of you and energizes you," says Mauk.

After 20 minutes warming up on an elliptical machine, Mauk works with a trainer for nearly an hour. Even after showering and changing, she still makes it to her desk at a nearby real estate investment company by 7:30 a.m. Mauk laughs when she realizes she gets more done in the early morning than most people do all day.

Vidoli feels the same way. "You're either going to sit in traffic and take an hour and a half to get to work...or you're going to get up and drive the speed limit all the way."

Vidoli reports an added benefit of hitting the gym every morning. Not only has he removed added stress from his life, but he's also lost 20 pounds. E-mail to a friend

Judy Fortin is a correspondent with CNN Medical News.