A TINY redhead with electric-blue shoes strikes up the carnival music. Sixteen people prance forward and backward in vague unison, grip their trapeze bars, tuck their knees in, yelp and swing. Welcome to ... the gym.

This Equinox class, which uses modified circus equipment as part of a cardiovascular workout, is called Jukari Fit to Fly, and it is just the latest in the collection of unorthodox classes that health clubs around the country have introduced. Yes, the bread-and-butter classes are still there — basic yoga, muscle toning, calisthenics — but often they are side by side with less standard fare like pole dancing or Army-style boot camp workouts.

At gyms that have made oddball classes into a hallmark, executives say they are trying to satisfy their clients’ increasing demand for novelty. At the Crunch chain, for instance, the goal is to introduce a handful of new classes every quarter, said Donna Cyrus, a senior vice president.

“We look very hard for entertainment in fitness,” Ms. Cyrus said. “I try to see what the trends are, and I look for instructors with theatrical abilities.”

Not all fitness clubs are so experimental. At New York Health and Racquet Club, the group fitness director, Maryann Donner, said that bizarre-sounding classes can draw members, “but if you have no idea what the workout is, based on the name, I don’t know how attractive that will be.” And some members still love “the very staid classes,” like Stretch, Sculpt, and Cardio, she said.

Carol Espel, the national director for group fitness and Pilates at Equinox Fitness Club, said that her company tries to avoid “programming fluff,” although it has offered classes like a Brazilian derrière-lift and Skinny Jeans Workout.

“We don’t want to offer something just because it was on ‘Oprah,’ ” Ms. Espel said. For example, “we would never offer pole dancing.”

But Equinox does offer Jukari Fit to Fly. The word Jukari is derived from the Sicilian word “jucare,” meaning “to play,” and the class, which was introduced in June in 14 cities, was developed through a partnership between Reebok and Cirque du Soleil.

The redheaded Equinox instructor, Sara Haley, said that Reebok sent her as a “guinea pig” to Cirque du Soleil’s Montreal base last year to see if any of its acrobatic equipment could be adapted for the gym. A team at Reebok and Cirque du Soleil then refined the recommendations and the result is the specially designed FlySet, which is like a trapeze, “but the ropes are way thicker, safer,” she said.

Among the people taking Ms. Haley’s class for the first time on a recent visit was Liat Kletz, a 28-year-old executive assistant. “I don’t love working out, so I look for ways to make it interesting,” she said. “I want to get fit without thinking about it.”

Near Ms. Kletz was Priscilla Vaccaro, who was taking her third Jukari class in two days.

“Yes, this is the weirdest class I’ve ever taken,” said Ms. Vaccaro, who also takes hip-hop dance, a samurai-sword class and a spinning class to gospel music. “I just turned 62, so this is a major thrill.”

Although unusual classes have cropped up around the country, they are often tested first in New York, where professional performers regularly double as fitness instructors. Ms. Haley, the Jukari teacher, is a former dancer. “I couldn’t pull off the waitress thing,” she said.

Ms. Espel of Equinox said, “New York City is definitely the laboratory.” Not only is the pool of instructors deep (most gyms hold regular auditions), but it’s also true that people are receptive to strange ideas, she said.

Across town at Crunch, Stacy Martorana, a dancer with the Merce Cunningham Repertory Understudy Group, was teaching an AntiGravity Yoga Wings class. Eighteen people hung upside-down from diaphanous hammocks suspended from the ceiling, their feet twisted in the fabric, as they tried to execute an “inversion” by flipping into a bat-like pose.

“If you’re new, you might feel dizzy or kind of sick to your stomach,” Ms. Martorana said cheerfully.

Like Jukari, Wings was adapted from a performance company, in this case, the New York City acrobatic troupe AntiGravity. Exerting mostly their upper bodies to complete poses like “right angle,” “mountain peak” and “airplane,” Crunch members learn to stabilize their weight with the hammock. “You have to trust it,” Ms. Martorana said.

Wings, she added, has been “crazy popular” since it began over a year ago. A waiting list is typical, and some members say they are addicted.

“I love it,” said Helen Lee, a 33-year-old marketing executive, “but I wish they would wash the hammocks. You’re in this wonderful nest, but it has that yoga stench.”

Crunch began in 1989 as a group fitness studio. Early classes included Aerobics With an Attitude (taught by a drag queen), Firefighter Workout and Kama Sutra Yoga.

In the mid-1990s, Ms. Cyrus said, Crunch decided to standardize the classes. “To tell you the truth, Firefighter Workout was not the safest,” she said.

According to Ms. Cyrus, 60 to 70 percent of Crunch members take classes, around a third of which feature some kind of twist, like a karaoke cycling class. The inspiration can come from popular culture (one class is pegged to a new TV show about weight-loss through dance), special equipment (like the Indo Board, a board on a roller) or a particular instructor (a class called Gridiron is taught by a former player for the Atlanta Falcons). “Dodgeball was big one year,” Ms. Cyrus said, while juggling did not make it past the idea stage.

The 1996 movie “Striptease” was the inspiration for Crunch’s popular two-year-old pole classes: Pole Dancing, Strip Bar, Turning Tricks and Pole-Lates. Watching Demi Moore on film, Ms. Cyrus said, she thought, “this is hard — it could make a really good class.” Crunch then got in touch with Kyra Johannesen, a choreographer who works with professional strippers.

At a recent, packed Pole Dancing session, Ms. Johannesen, a tall, athletic blonde with conspicuous bruises on her thighs from gripping poles, guided me through a few basic moves like the walk-around, fan-kick and crawl. Although I found it impossible to perform certain flourishes — like patting my bottom through my legs — the pole itself was fairly manageable to climb up and slide down.

“The hardest part is walking into the room and saying, ‘I’m going to be O.K. with myself,’ ” Ms. Johannesen said.

Rosa Richardson, a teacher from Brooklyn, showed no fear as she mounted the pole and spun around it in six-inch Lucite heels (many students bring their own stripper shoes). “You’re lifting your own body weight up the pole, and I have a lot of body to lift,” said Ms. Richardson, who has taken a pole class almost every day for a year.

“She’s pretty gangsta,” said Tara Crichlow, the assistant instructor, of Ms. Richardson’s performance. “You’ve got to give it up for the thicker girls.”

Solidarity is a major element of the class, which ends with a free-style demonstration by each participant, who is cheered on by the rest of the “pole team.”

“It’s massively about female bonding,” Ms. Johannesen explained.

Gender does play a role in boutique gym classes, many of which are targeted to women. New York Sports Club, for example, offers Catwalk Confidence, in which a podiatrist teaches women how to walk properly in high heels, and Pilates Together, where mothers use their babies as weights.

Men are strangely undeterred from Knockout Bride, an intense cardio-kickboxing class at New York Health and Racquet Club that is designed to get brides in shape for the big day. (“Remember, all you have in the end are the photos,” said Ms. Donner, the group fitness director, who devised the program.)

“All my co-workers make fun of me for coming to Knockout Bride,” said Kevin Nadolny, 27, a structural engineer, at a recent class in the financial district. Mr. Nadolny is marrying in August, he said, “but it’s a coincidence.”

Craig Walker, a lawyer from Brooklyn, said he “had no idea” that the class was geared toward brides. All he knows is that “it’s torture” and that it has helped him whittle his body fat.

The class, which can last from one to three hours, entails constant motion of the arms and legs, usually on a small trampoline called a rebounder and always to a jarring medley of music (from 50 Cent to Marvin Gaye to Mr. Mister).

Members have been known to break down and cry, said Leo Wright, the instructor, who started his fitness career by teaching boot camp at Fort Dix. “People run out when they can’t take it anymore, but they always come back,” he said.