Parkour started as a sport for the young and bold. But now it's expanded to new groups as an answer to traditional-gym boredom. (Gabe Silverman and Jeff Simon/The Washington Post)

Nancy Lorentz crab-walked up a flight of stairs at Tide Lock Park in Alexandria, Va., one recent weekend. She twirled over the railing on another set of stairs, twisting her hands and tilting her body into an almost-fetal position before landing on two feet like a street ballerina.

Although her agility seemed almost effortless, the 52-year-old mother of three might not be considered a typical practitioner of parkour, a kind of urban gymnastics in which participants use everyday objects — street lamps, dumpsters, cars — as ad hoc obstacle courses.

But the sport, made popular by movies such as “Casino Royale” and the Jason Bourne series, isn’t just for teens and 20-somethings.

“It gives you a whole new way of looking at things, and it gives you confidence,” said Lorentz, who lives in Alexandria and has been practicing the discipline for a little more than three years. “It’s just so beautiful when you do it correctly and you’re moving quickly through an alleyway and hop over some fences instead of finding the gate. It’s nice to do what your body is meant to do.”

The sport does not have a governing body that keeps detailed statistics about the ages of participants. But leaders of parkour gyms in the Washington region have begun responding to an uptick in demand from an older clientele.

Alexandria-based Urban Evolution, which runs a chain of parkour gyms, created a class exclusively for participants 35 and older.

The American Parkour Academy in the District has added adult classes and said that the number of patrons who are 30 and older make up about a quarter of their business.

And weekend warriors in their late 20s and older, such as the members of the two-year-old Washington DC & NOVA Women’s Parkour Meetup, have begun holding informal gatherings of participants around the region.

Parkour, which originated in France in the late 1980s, has seen a surge in popularity during the past decade thanks to social media, YouTube and the millennials who make up the bulk of its devotees. Its popularity has turned heads and made headlines after some practitioners attempted high-profile stunts, such as one performed by a man who climbed the Eiffel Tower.

But the sport’s older enthusiasts say that despite its perilous, cover-your-eyes acrobatic movements, a version of parkour can provide a surprisingly gentle and effective workout that is kind to achy bones and arthritic knees.

“It’s like just playing in the playground,” said 49-year-old Christie Thomas of Lorton, Va., who started practicing parkour four years ago after watching her 10- and 16-year-old sons try the sport. “It brings the kid out in you.”

Christie Thomas, 49, of Lorton, jumps onto a railing at Gateway Park during a parkour jam session in Arlington. (Pete Marovich/For The Washington Post)

Pete Waterman, a coach at the American Parkour Academy, said that he felt old when he took up the sport six years ago at 32. Now, he said, it’s not uncommon to work with clients who have a decade or two on him.

Waterman, 38, said that he finds many adults are drawn to the obstacles that they find in parkour.

“You really have to challenge yourself physically and mentally in a way that you don’t challenge yourself in other things,” said Waterman, a vice president at a technology company. “If you want to get better at golf, you just golf more. You want to get better at parkour, you have to jump further over a higher gap that is scarier and harder, where you could break your leg.”

Because of those risks, medical experts recommend that older parkour enthusiasts start slowly in a safe, controlled environment. They say it also helps to have a basic level of fitness, balance and body awareness.

Janet Vasak, 69, recently left her first parkour class in Alexandria and said that she felt refreshed in more ways than one.

“Once you age and you become sedentary and your muscles firm up and you can’t do things, mentally it gives you an impression of a loss of abilities and it puts you in the mind-set of ‘I’m less than what I used to be,’ ” Vasak said. “And I don’t want to look at the coming years [that way] — I’m still a vibrant person.”

Salil Maniktahla, 43, of Arlington, Va., was laid off from a tech job in 2010. He cashed out his 401(k) to start a chain of gyms that teach parkour. He said it was an advertisement he saw on YouTube, featuring parkour’s founder, that got him hooked three years prior.

“Fitness shouldn’t be boring,” said Maniktahla, who went from avoiding the gym to going as often as he could after discovering the discipline. “It shouldn’t be something you do to tune your body and that’s it. We really believe parkour is for everybody, not just 18-year-old boys or teenagers. It’s about learning to get back in touch with your body.”

Before taking up parkour, Lorentz said she was often shaking and achy — a self-described professional layabout. But since starting her training, Lorentz has stopped taking her arthritis medication, lost 50 pounds and pulls off vaults, rolls and climbs with ease.

“Most people have a Porsche and only drive 25 miles per hour all the time,” she said, comparing the human body to a sports car. Parkour, she said, “makes you step on the gas.”

She said her journey as a traceur — a parkour practitioner — started as a joke. After enrolling her three children in classes, she thought: “I’ll try one before my 50th birthday.” Now, she travels to gyms across the Washington region and has given herself a personal challenge to swing a parkour move in every state. And she swears that the fitness she gained from parkour training helped her during a bout with breast cancer.

After surgery, she went right back to the gym. Lorentz, who no longer colors her silver locks, wants to spread her love of the sport — and the strength she found in it. She created an organization called the Parkour Movement Foundation that plans to focus on teaching the elderly modified parkour moves to help them gain balance and strength.

One of the sport’s pioneers said he hopes that is a central takeaway for traceurs of any age.

“When you learn a jump, you learn full commitment — you can’t stop in the middle,” said Sébastien Foucan, who helped develop parkour in the 1980s and is credited with founding freerunning, a spinoff of parkour that is a little more acrobatic with more martial arts.

Foucan is 39 and a father. He teaches parkour to those of all ages, even, he says “youthful adults.”

In a telephone interview from his home in London, Foucan said the sport is not about jumping from roof to roof, but about how to move through life.

“You start to face these difficulties, and then you realize: ‘Oh, can I apply the same thing I learned through my practice without the movements?’ ” he said. “Then you start to experiment again and that’s where, for me, you become a freerunner. You learn to let it go.”