Health

The sexy (and sweaty) workout Emma Watson loves

305 Fitness has the kind of storefront that catches a person’s attention.

“OK, I have to ask. What IS this place?!” shrieked one woman who barged into the lobby on a recent Wednesday evening.

What piqued her curiosity? The massive, hot pink “GIRLS GIRLS GIRLS” sign plastered on the wall above the Greenwich Village studio’s minimalist white front desk.

This is exactly the “Art Basel-meets-nightlife energy” feel that creative director Kibwe Chase-Marshall wanted to convey inside the space: “When I’m at gallery shows and they’re playing music, I’m always like, ‘I. Wanna. Dance. But I can’t.’ ”

Now he can. The newly erected studio, open to the public as of last Thursday, houses two large rooms complete with live DJs, where students shake, shimmy and jump — until they’re dripping with sweat and glowing with endorphins.

Billed as a “rave meets workout,” 305 Fitness fuses dance with sports drills, high-intensity interval training and a set list of pop, EDM and hip-hop.

“I’m always super, super sweaty; it’s the sweatiest I ever get with any workout,” says regular Patty Kim, a 28-year-old account manager, after walking out of an evening class taught by Sadie Kurzban, the 24-year-old founder and owner of 305, which, until now, has operated as a roving dance party.

The DJ is more important than the trainer at this hot workout scene rivaling any late-night club in town. Classes feature a live DJ (above).Brian Zak/NY Post

A self-professed “raver baby,” Kurzban is no stranger to sweat. Having grown up in body-conscious Miami, she felt the pressure to join the calorie-burning game. “I grew up a slave to the treadmill, the elliptical … trying to purge myself of calories like many self-conscious young women.”

That all ended when she discovered dance as a teenager. Before long, she was “surrounded by this community of people who wanted to move just to move,” and started “appreciating what my body could do for me.”

While attending Brown University in 2008, she made a hobby out of teaching dance-inspired fitness classes on campus.

But it wasn’t until a fateful night out at a Miami club during a 2011 spring-break trip that Kurzban had “this epiphany of joy when you’re with your buddies and sweat is dripping down and there are people around you and it just kind of clicked.”

When she got back to Brown, Kurzban began making playlists and partnering with local DJs for a class she dubbed BodyRox.

It didn’t take long for word to spread. Eventually, “kids would line up around the block” just to squeeze into her sweat sessions.

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One of those students was actress Emma Watson, who regularly attended Kurzban’s class while studying at the university.

In 2012, Kurzban turned her fledgling class into a booming underground business in New York. She renamed it 305 Fitness in a nod to her hometown’s area code, and got funding from friends, family and a Kickstarter campaign that raised $32,000.

305 Fitness developed a cult following, but for two years it was “literally underground, in the basements of weird gyms in New York,” says Kurzban.

Jack Solomon, 25, discovered the class two years ago when he weighed 220 pounds — he’s since lost 80 pounds. “It’s just been like a party the entire time,” says Solomon.

Shira Atkins, an editor at a health and wellness publication, says she didn’t join to lose weight, but says the biggest physical difference she’s noticed is “mostly in my a - - .”

The newly opened studio has common luxuries that students once did without: “We have bathrooms, showers, all that stuff,” says 305 Fitness trainer Latoya Jul’ce.

305 Fitness boasts flexible trainers like Latoya Jul’ce.Brian Zak/NY Post

Jul’ce, who’s been teaching at 305 Fitness for two years, says members get a certain confidence boost from “grinding your booty against girls you don’t know.”

Not a typical thing to do at the gym, but when the lights are dim and there’s a live DJ in the corner, all bets are off.

The live DJs improvise each class, so no two are identical. “Having a live DJ in the class makes a difference,” says regular Allie Landuyt, a 24-year-old junior planner. “Because they control when the music changes, you don’t have to wait for the perfect part of the song — they do it for you.”

305 Fitness, 18 W. 8th St.; 646-480-2459, 305fitness.com; $32 per class; special promotion: $36 for 3 classes