NEW YORK - More exercisers are taking their fitness to the air these days, held aloft by technology borrowed from sources as far-flung as the space program and the circus.
Experts say if you adhere to the learning curve, going anti-gravity can be just the thing to relieve overused joints and revitalize an earthbound routine.
Stephen Csolak, fitness manager at a Manhattan branch of Equinox, the national chain of luxury fitness centers, uses an anti-gravity treadmill, called Alter-G, on a range of clients, from marathoners to the morbidly obese.
"You have this bubble around you and you're floating on top," he said, describing how the Alter-G, which was developed from NASA technology, uses air pressure to gently lift the user.
"If we remove a percentage of someone's body weight by altering the effect of gravity, we come up with a lot of different benefits for a lot of different populations," he said.
So marathoners can train for speed and endurance with reduced risk of injury, older adults can exercise with reduced pressure on their joints and the obese can work out unencumbered by their extra pounds.
"Being on the anti-gravity treadmill allows the obese client to feel their target weight, what they'd feel like if they were nine, 14 or 18 kilograms lighter," Csolak said.
First lessons on the Alter-G are supervised, he said, and clients get hooked easily because it's such fun.
"I don't believe there's anything like it, other than swimming," he said. "Swimming's also a zero-to-minimal impact cardiovascular workout."
Jessica Matthews, a spokesperson for the American Council on Exercise, said she's seeing more anti-gravity group fitness classes.
"I think of anti-gravity as anything where you're physically suspended," said Matthews, a California-based exercise physiologist.
Offerings range from yoga classes where participants hang from hammocks, to group instruction in executing Cirque du Soleil-style stunts.
"There can definitely be a place for this," she said. "But in a group setting, when you have 30 to 40 people hanging upside down in a room, safety is key."
Sabrena Merrill, a Kansas City, Missouri-based fitness expert, has developed a fitness program that uses aerial silks suspended from the ceiling.
She said her goal is to bridge the gap between the performance and fitness worlds.
"Climbing silks, doing foot locks and body wraps twice a week in lieu of resistance or weight training, definitely works the body hard," Merrill said.
The mechanics of being in the air forces your core to work differently, she explained, but the focus of her workout remains on the basic components of strength, flexibility and endurance.
"Most women can't imagine doing a pull up," she said, "But after this training, they will do a pull up. Upper body strength will change."
Merrill, who trains fitness professionals in the class, agrees that safety is crucial. Clients are screened for pregnancy, high blood pressure and medication.
"We just don't go very high off the ground, about one foot off the ground for most. And there's a protective mat underneath," said Merrill.
She doesn't contend that the aerial silks workout is superior resistance training, but it might be more fun.
"It's not better or worse, just different," she said. "I can't stress enough the enjoyment of the play. You feel like you're a circus performer."