For David Gomez, jumping down a staircase comes almost as naturally as walking down its steps. He can flip backward or forward from the top, do a handstand on the railing or just casually walk up.
Whether he chooses to defy gravity depends on how strong an urge Gomez, 22, of Bayport, has to begin a sequence of parkour moves.
Parkour is a series of movements based on a training discipline that involves climbing, jumping, running, rolling and balancing -- ranging from diving off rooftops to scaling walls -- and is usually done on hard surfaces in urban environments. The purpose is to build mental and physical strength, swiftly traverse obstacles and reach a destination, all without falling down. It was developed in France in the late 1980s and gained popularity in the West in the mid-2000s when it was featured in mainstream action movies, such as the James Bond film "Casino Royale" and the Jason Bourne series. Social media have boosted parkour's allure by allowing people to share videos of their moves.
"Nowadays, kids see all these [parkour] videos that get so much hype and they see the people who do it are very healthy, active and cool to watch that the underground has kind of disappeared," said Gomez, a hardware technician. "It's kind of like how skateboarding went professional."
Parkour has its roots in French military obstacle training courses from World War I and II designed to increase soldiers' ability to move in battle. It has spawned two offshoots -- freerunning and tricking.
A typical parkour sequence may start with vaulting from one rooftop to another, making a way inside the building and then leaping down a staircase to reach the ground floor. While a parkour enthusiast would simply jump over a wall in his path, a freerunner would scale it and then leap off doing a back-flip.
Tricking is a mix of jumps with flips and twists, martial arts kicks and break-dancing moves in a finite space and on more forgiving surfaces than those used in parkour.
Gomez leads Genesis PKTK, a group of about four parkour enthusiasts and seven trickers. Earlier this summer, the team held regular tricking practices at the beach in Smith Point County Park in Mastic. Their parkour training sessions, which take place about twice a month in Port Jefferson by the harbor, become spectacles often captured on spectators' phones.
Matt Jones, 16, got hooked on parkour two years ago after seeing a YouTube video of a stuntman re-enacting scenes from a video game. Jones, of Rocky Point, said he was slightly overweight in middle school and likes that parkour can boost fitness.
For Jones' father, Mark, 52, parkour is more than just a hobby for his son -- it helps keep him alive. Matt Jones has had juvenile diabetes since he was 12. Parkour ramps up his metabolism, lowering the number of insulin shots he has to take.
"I'll support him any way I can," Mark Jones said. "He's not jumping off of buildings; not yet anyway."
Max Henry, 22, of Malverne, is jumping off trucks when he's not teaching parkour at The Movement Creative, a Manhattan-based community outreach organization. In an American Eagle Outfitters commercial playing in Times Square, Henry does a forward flip from the back of a pickup truck, vaults over the roof and sails over the vehicle's hood wearing the brand's new line of flexible jeans.
Though Henry, who has eight years of parkour experience under his belt, said he would earn more money by putting to use the bachelor's degree in math he earned from Hofstra University in 2014, teaching parkour is his passion.
"As you teach more often, you meet people who say, 'I really think parkour is amazing, but I could never do that; I'm not fit enough, I'm too fat, I'm too old,'" said Henry. "Eventually, if they stick with it, they'll be able to get it."