Gabe Streisfeld, 18, grabs a metal pole on a loading-dock ramp in an alley next to the Comcast Center. It feels sturdy, anchored in a cement ledge, so the Penn Valley native takes a few running steps, leaps up about five feet, and swings his whole body around.
His longtime friend Ty Soehngen, 18, of Narberth, suggests they swing halfway around and jump onto a ramp a foot higher. He flies off the pole and grabs a rail above the ramp to hoist himself over.
For Streisfeld and Soehngen, Center City is a grown-up's playground. Both are devotees of parkour, an extreme sport created in France almost 20 years ago that migrated to the United States about six years ago, and more recently to the Philadelphia area.
Through the eyes of traceurs (traceuses, for women) - the name for those who do parkour - railings, walls, and stairways are obstacles to conquer, not avoid. Traceurs do not wear protective gear, earning the sport a reputation for being dangerous.
In the last five years, parkour has become more popular thanks to YouTube videos of experts jumping across rooftops and traceur cameos in action movies such as Casino Royale and The Bourne Ultimatum.
On June 3, Streisfeld, a recent graduate of Harriton High School, posted his own YouTube video, "A Day in Philly," as a way to promote the small but growing Philadelphia scene. Working the camera was Drexel University senior and fellow traceur Tom Quigley, 21, who is also a video intern for Philly.com.
The video shows Streisfeld running, climbing and jumping outside 30th Street Station, the Philadelphia Museum of Art, and City Hall, common spots for local traceurs during weekend practices.
But since the city is uncharted territory for traceurs in other U.S. cities, Streisfeld said he hoped the video - now being linked to on local blogs and parkour Web sites - would encourage them to visit.
"Philadelphia is completely undiscovered," he said. "I wanted to get the word out."
Parkour was created in France in the 1980s, based on a type of military obstacle-course training called parcours du combattant. It came to the United States as videos spread online, according to Mark Toorock, who runs a national parkour hub, American Parkour, in Washington.
He estimates several thousand people - mostly young men in their 20s - around the country practice the sport.
Streisfeld, who will attend the University of Pittsburgh in the fall, began practicing three years ago after watching parkour videos online.
The appeal, he said, is the opportunity to exercise outside the confines of a gym. He said he was nowhere near as fast or strong as the experts but enjoyed the challenge of pushing his body.
"Cavemen didn't have workout machines," he said. "You get strong by working out in your surroundings."
Soehngen, who just graduated from Lower Merion High School and will attend Drexel University, added that he likes the "renegade aspect" of parkour.
"People in general don't take advantage of things our bodies are capable of," he said.
Streisfeld and Soehngen help coordinate the Philadelphia scene through an online forum. About 20 people meet up for weekly practices around Center City; as many as 40 come to monthly jams.
But despite parkour's growing popularity, Quigley said, traceurs around the world are engaged in a public-relations battle because of the sport's reputation as reckless.
"We try to get the right image out," Quigley said. "I think it's an attractive image because parkour is freedom . . . with your body."
Safety is the top priority of parkour, according to Toorock.
Beginners are encouraged to practice in groups, honing their jumping, landing, and rolling skills.
"If someone just goes out and starts jumping on things or off things, they will inevitably get hurt," Toorock said.
Streisfeld said he has been seriously injured once since taking up Parkour - he fell on his shoulder this year during practice at the gym, damaging soft tissue. It took eight weeks to heal.
Doctors at area hospitals said they had yet to see a rise in parkour-related injuries but were concerned about the sport's growing popularity.
"Parkour magnifies what some of the routine sporting injuries are because of the level of what they're doing," said Steven Cohen, director of sports-medicine research at the Rothman Institute at Jefferson University Hospital. Cohen, who is familiar with the sport but has never treated a parkour-related injury, said parkour placed nearly every part of the body at risk of bruising or breakage.
He recommends at least wearing a helmet, if not other protective gear. Another concern, Cohen said, is the lack of safety warnings on videos available online that show more extreme stunts, given how popular they are among young people.
Traceurs also face scrutiny for their use of city spaces. Streisfeld said he is asked regularly to leave private parking garages and other spots in Center City.
In public places, traceurs are free to practice as long as there are no signs prohibiting use, according to Officer Jillian Russell, a Philadelphia police spokeswoman.
The problem, Toorock said, is when passersby become uncomfortable about traceurs' unusual behavior in public.
"At a certain age, it becomes unacceptable to play," he said. "If a 38-year-old man climbs a tree . . . people don't know how to deal with it."
Young traceurs like Streisfeld can face an even tougher dilemma: explaining the sport to nervous parents.
Streisfeld's father, Neil, said he and wife Donna were "not really thrilled" when a 15-year-old Streisfeld, the youngest of three children, announced his plans to jump around the city without a safety net.
"We support him, but with our fingers crossed," Neil Streisfeld, an endocrinologist, said.
For the original YouTube video, "A Day in Philly":
For the Philly Parkour online forum:
For the American Parkour Web site: