NEW YORK >> First-time documentary filmmakers Tina Brown and Dyana Winkler lugged their cameras to Central Park in New York one day to capture the last few people still passionate about roller skating. Rinks across the country were gone. The activity seemed dead.

“We were shooting a piece about what we thought was the end of the era of skating with what we thought were the last men standing,” said Winkler. “We thought, ‘Who roller skates anymore?’”

They may have come for a funeral but they found something else entirely. Two young African-American skaters approached them and asked them what they were doing. “They said, ‘Skating’s not dead. It just went underground,’” Winkler recalled.

Winkler and Brown decided to go find it. Five years and 500 hours of footage later, they’ve emerged with the HBO film “United Skates,” a fascinating look at the rich African-American subculture of roller skating, which is under threat.

“We hope that our viewers will learn something they didn’t know about, fall in love with something they didn’t know about, and maybe be compelled to care enough to protect it,” Winkler said.

The documentary explores how roller rinks were the sites of some of the earliest fights of the civil-rights era and how they later became the launching pads for hip-hop artists.

It shows how unofficial segregation lives on, with so-called “adult nights” that feature metal detectors and masses of police, something not used when whites come to skate. It also shows how rinks are being closed as communities chase more revenue by rezoning for retail use.

“There’s a bigger story to tell and we can use the joyous beauty of roller skating as the sugar to spoon-feed some of these bigger issues. That’s when we started to peel back the layers,” Winkler said.

That day in Central Park changed the trajectory — and the lives — of the filmmakers. The young skaters they met invited the women to come and see what had happened to skating. And so they got on a night bus to Richmond, Virginia.

The duo — one Australian, one American — approached a roller rink at midnight. It was far from funereal: There was a line down the block, music was pumping, skaters were dressed to kill and everyone seemed to know each other.

“We stepped into this world,” said Winkler.

They soon learned that each city had different skate dance styles — Baltimore has “Snapping,” Atlanta has the “Jacknife” and in Texas you do the “Slow Walk” — and how such a tight fellowship among skaters is forged that they will fly across the country to get together.

Embraced by the community, Winkler and Brown never paid for a hotel room or car rental or a meal while crisscrossing the country interviewing some 100 skaters. The skaters themselves opened their homes and drove them around.

The documentary features interviews with hip-hop legends like Salt-N-Pepa, Coolio and Vin Rock of Naughty by Nature. John Legend is an executive producer and the film received the Documentary Audience Award at the Tribeca Film Festival.

The cameras also follow Reggie Brown, a roller-skating ambassador and community advocate. In a phone interview, he explained that roller skating teaches patience, athleticism, purpose, positive reinforcement, determination — and getting up after a fall.

“Roller skating is a little bit more than going in circles on a couple of wheels,” he said. “It’s fun. It’s an enjoyable exercise. It’s healthy and there are a lot of great benefits. But the socioeconomics benefits to roller skating are higher than anybody can think of.”

“Name me another activity that’s family-affordable, that you can go to on a Saturday and take five members of your family and you can skate for four hours and everybody can have a good time and exercise.”

“United Skates” is a documentary made partially by the subjects themselves. Winkler and Brown, who began the project as beginner skaters, enlisted skaters to shoot scenes and used their rink skills to help capture footage.

“They would push us from behind at these high speeds and we would just focus on the camera and just pray,” said Winkler. “It really was collaboration. They like to say we taught them how to shoot and they taught us how to skate.”

The cameras capture one suburban Chicago family-owned rink’s gut-wrenching decision to shut its doors — among thousands that have done so in the past decade — and the filmmakers are not shy about hoping their film can stem the tide of closures.

“Obviously if we could save one rink, if we could have one rink reopen because of this film, that’s a huge step forward for this community and we hope that will have a ripple effect,” said Brown.