Avant-Barre is a genuine group-exercise unicorn — a truly adaptable workout that allows participants of a wide range of fitness levels to get involved, but still keeps every member of the class pushing hard for the full hour. You'll leave the class feeling fitness is attainable, and maybe even... fun? Yes, fun.

Bay Area native and Avant-Barre founder Nini Gueco had been a dancer and instructor at another San Francisco barre studio before getting frustrated by what she describes as the "redundancy and strictness" of the discipline's traditional mix of Pilates-like small movements, body weight exercises, and stretching.

From that frustration sprang Avant-Barre, which puts a new spin on the form with the addition of circuit-style sets, dynamic full-body movements, and just enough cardio. Add to that enthuastic but human and approachable instructors, and the kind of music that makes you want to move (example: at one recent class, non-stop Beyoncé), and you can see why classes at the SoMa studio frequently require a waiting list.

Just as important as the movements is the atmosphere — after all, if you don't care about the environment in which you're working out, just do an exercise DVD and call it a day, right? A lot of emphasis is placed on Avant-Barre's "upbeat, fun, and welcoming environment," and this isn't just lip service. During an Avant-Barre class, you'll see none of the gritted-tooth determination to get it right or else from the men (yes, men) and women in your class, nor will you get the side-eye (or, worse, an instructor call-out) if you must adapt movements to match your current state of fitness.

That said, you'll still be challenging yourself throughout your routine. Cori, the instructor who teaches classes on Mondays and Tuesdays, demonstrated a near-supernatural ability to detect just how much harder the class could push, while still letting individual participants know it was perfectly OK to dial back.

Moving through demanding arm work — "people ask me if we use weights in these classes, and I say 'just try holding your arm up for as long as we do! You don't need weights,'" said Cori — a demanding core series, a ton of leg work, and a glute combination that had everyone in class groaning, the class passes by in a flash. The variety of movements, the supportive environment, and Cori's guidance made the session seem more party and less like the begrudging chore that exercise can sometimes be. Beyoncé didn't hurt, either.

After class, Cori said that before she took up barre and yoga, she "was lifting more (weight) than a lot of guys" and playing basketball. Since then, she's "lost 10 pounds" and feels "stronger at 39 than I did in college."

Looking at the enviable muscle definition on many of my fellow Avant-Barre participants, a few who confirmed that "this is all (the exercise) I do," it's easy to believe that she's not alone. Hmmm, maybe there's something to looking at fitness as something other than grim, competetive hours at the gym, after all.

Avant-Barre is located at 592 Third Street, at the corner of Brannan Street in SoMa. New clients can purchase a single class for $20, or an unlimited 30 days for $99.

GEAR

• Wear a close-fitting shirt that won't ride up, bind, or expose anything as you bend and lean.
• Class attendees are asked to wear close-fitting pants, but the studio can get really hot! So shorts are also acceptable, but keep in mind you're going to be putting your leg up on a barre while the other is on the ground, so make sure those shorts are close fitting, and won't ride up to show classmates parts of your body they'd prefer not to see.
• If you're shy about your feet, you can wear socks, but the class seemed easier without them.
• A mat and a strap are laid out and provided. Don't forget to grab a towel (also provided) when you walk into the studio! You'll need it.