CHAPEL HILL - From the training floor of Kinetix in Chapel Hill, those running on a tread mill or muscling up to the pull-up bar can see inside the windowed group fitness room.

Twice a week they can see the women, lining up like they’re trying to get into an exclusive VIP party, grasping at the plastic cards that give them entry to the one hour that day when they get to dance and jump and hip-check in a flurry of sweat and bumping bass.

They line up around the stage where Eric Ziegler stands; some begin stepping in place, some stretch. The music starts, then Ziegler starts, and then the army of (mostly) women start too, moving through the musical genres of the dance workout Zumba

Ziegler takes participants on a fast-paced aerobic tour of dance genres including Bollywood, Latin, hip hop, reggae ton, merengue and pop. Women shriek and cheer like they’re at a manic workout rave, trying to mimic his moves.

They could be anywhere; the streets of Havana, in a Bombay market, dancing with Justin Timberlake at a Los Angeles club, in the arms of a Latin lover in Mexico City.

Unhinging his hips, Ziegler effortlessly squats down then up, shaking it all at an eyebrow-raising speed.

You get the sense that many of the women in the room didn’t discover that they too, have these things called hips – and an apparent ability to shake them real fast like they’re trying to jumpstart a motor or rotate them real slow like they’re churning butter – until they took Zumba with Ziegler one Saturday afternoon.

Always smiling, Ziegler has the defined muscles of someone in a gym ad or music video.

He has an magnetic energy and excitement about every foot-kick, squat, and booty shake he does, his body language shouting, “Come and dance! It’s most fun thing ever!”

“I wanted to be the kind of instructor that when someone mentions my name they know the kind of workout they’re getting,” he said.

Apparently, they do.

At Kinetix, the classes have become so popular, the gym caps them at 35. Members have to register online exactly 24 hours before the start of each class to get the first 20 spots, or hope to get one of the remaining 15 the next day in person. The loyal stand in line 30 to 40 minutes before the class begins to get an entry card.

“We were getting to the point where it was dangerous,” said Kerry Brandewie, group fitness director at Kinetix in Chapel Hill. “There’s a lot of swinging elbows in Zumba.”

Zumba boasts a high-calorie burn and intense cardiovascular workout and Ziegler tailors his workout with high-energy songs, targeting certain muscle groups and parts of the body like thighs, glutes and abdominals. He often moves around the room, dancing alongside women gyrating at their reflections.

The teacher at Smith Middle School in Chapel Hill often team-teaches with his wife, Valine, and choreographs original dances to contemporary music with help from his three children. He spends hours on one dance, making sure each class offers something new.

“We decided we wanted to give people an unforgettable experience when they take our class,” he said.

Zumba has continued to grow in popularity throughout the Triangle and across the country, and demand for Ziegler’s classes have spiked too. He and his wife became instructors, now Ziegler says they’re the only black husband-wife instructors in the Triangle.

“We do this together so we can be together, so we might as well create together,” he said.

Ziegler is typically the only man in the room when he’s leading Zumba, save for one or two that pop in on occasion

Though the creator of Zumba, Colombian fitness instructor Alberto “Beto” Perez is male, it is rare to see guys leading classes, said Loretta Bates, a Zumba education specialist, who based in Cary, but travels all over the country teaching Zumba instructors.

But more men are becoming interested in Zumba, she said.

After Zumba with the Zieglers on Saturday morning at Ephesus Church Road Elementary School, Pat Blau, 60, follows her classmates out the door.

“You saw all the energy in there,” she said. “I feel like I’m getting an incredible workout and at the same time having fun.”

For Kate Behrenshausen, 28, Zumba is a time for her.

“It’s refreshing after a long week to forget about everything else,” she said.

That’s the goal..

“[Zumba] belongs to everyone,” Ziegler said. “I feel like for one hour I’m able to help someone focus on themselves and enjoy life through fitness and that feeling is exhilarating.”

Legs and hips bounce in place, arms swivel up and down and around until the slow music dampens the sweaty, high-tempo fervor. The wind-down begins with a rotating of the wrists and neck.

Then his head drops, and Ziegler bows in a monk-like movement of thanks. His hands move together like a prayer, he raises them to his forehead and thanks everyone for coming.