Parkour, the free-wheeling outdoor sport of vaulting, bouncing, jumping and flipping through the urban jungle, has inspired a new breed of indoor fitness centers where buildings are boxes, sidewalks are mats and caverns are foam pits.
Fitness experts say the soft landings, controlled environment and instruction in these gyms have transformed the risky pastime of urban youth into a fitness option accessible to just about everyone.
"We're not just a gym, we're an educational facility," said Ryan Ford, co-owner and instructor at Apex Movement, a Boulder, Colorado-based chain of parkour gyms in Colorado and California.
"People can learn from a fake environment with instructors."
Ford, 26, stumbled across parkour on the Internet in 2004 when he wanted to learn how to run up a wall.
At Apex, where clients range from five to 75 years in age, it is all about breaking down each movement into constituent parts, and progressing through skill levels.
"What we do is often misunderstood," Ford said. "People think it's all flipping off walls, jumping off buildings, but that's not true. If a 75-year-old has trouble ducking under rails or standing on a bench, that's where we start."
The emphasis, he added, is about regaining the natural ability people had as children.
Phil Pirollo, the 29-year-old owner and instructor at Pinnacle Parkour Academy which has two locations in southern New Jersey, said a few years ago there were just a handful of parkour gyms across the country and now there are probably close to 50.
His gyms feature bright colors, different shaped obstacles, boxes and rails that replicate the reality television show "American Ninja Warrior," in which contestants compete through a parkour-type obstacle course.
"People adhere to it like a cult," said Pirollo, whose business is 90 percent male and mostly ages eight to 15.
"Kids are going out, climbing jumping anyway," said Pirollo, who has been teaching movement for 10 years. "With this they're becoming cool, getting an identity. It's like skateboarding without the skateboard and parents like the idea that we teach it properly, in a controlled environment."
With no treadmills, no weight machines and no televisions, he said, the gyms resemble adult playgrounds more than traditional fitness facilities.
"Consumers come in the door, film themselves and then post themselves online," he said. "It may be a teenager doing his first back flip, or a kid who gets up and over a wall."
Dr. Mark P. Kelly, an exercise physiologist with the American Council on Exercise, said parkour involves not just strength, speed and agility, but also coordination and balance.
"Even hand-eye coordination, being able to grab a bar quickly in the air," he said, adding that teaching parkour-type activities in a gym can be safe with proper preparation and conditioning.
"I think it's a great movement to move indoors," he said. "You see kids outside riding skateboards on railings and not getting the proper instruction and conditioning to do it."
Kelly, who attended a parkour workshop at age 50, said its philosophy fits in nicely with the movement towards functional fitness, where exercise mimics everyday activities.
"It's all about practicality," he explained. "Our instructor said, ‘We don't do a pull up for the sake of a pull up. We pull up onto something.'"
He said the gym setting can help remove some of the fear which can limit the development of movement skills."I think the gyms could bring a lot of people to this fun style of fitness," he said. "Back in my day we did parkour. It was called play."