New York: Surfset Classic
What to expect: Pop up on the RipSurfer X, a machine that looks like a real surfboard, wobbles as if on water and comes tricked out with bungees at its nose that allow you to "paddle" with resistance.
Know before you go: Exactly as you would for the real thing, ditch socks for a better grip on the board.
Your turn: Simulate a sick set while you define a surfer-girl chest: Get in push-up position with hands on a BOSU ball; push off the BOSU, and explode to standing. Gnarly!
More: Sculpt Your Body With a BOSU ball
"Physique 57, Physique57.com, one of the first NYC barre classes, is a tough thigh, butt and ab workout that never lets me down." Nicole Catanese, fitness director
"The NYC boot camp class As One, As1 Effect.com],makes whipping ropes and leaping over boxes feel doable—and even fun." —Marissa Stephenson, fitness editor
"In Deep Extreme, Equinox.com, yoga moves are mixed with tribal dance to give a bigger cardio burn." —Jaclyn Emerick editorial assistant
Say bienvenido to sculpting sexy curves and sizzling mucho calories! Here, every day is a bikini-baring opportunity, so it's no surprise the hottest workouts aim to burn as they firm.
Miami: RealRyder Inferno
What to expect: Picture indoor cycling but on a bike (called a RealRyder) that pivots side to side so you can lean into twisting trails, just like on an alfresco ride (you might feel like you're outside, too, in this studio of wall-to-wall and floor-to-ceiling windows!). Twice, you'll crank the resistance to slowpedal while you do 15-minute lifting sessions with 3-pound weights.
Know before you go: The bike's instability means you're firing your core to stay balanced the entire hour.
Next stop: chiseled abs!
Your turn: Class goers here have a "bike butler" to help them adjust height and handlebar settings, but you can ask an instructor in any class to customize your ride's fit.
More: Benefits of an Indoor Fitness Class
Miami: Dance Street Lab
What to expect: The sounds of Miami—Latin rap, Jamaican reggae and salsa—accompany music videoñesque moves. And you don't have to be Shakira to hang. The first three songs are your warm-up, and the steps you learn (slowly!) provide the foundation for mastering the rest of the hour-long class.
Know before you go: DSL is so caliente that students spill into the hallways. Aim to arrive 20 minutes early.
Your turn: No matter what dance class you're in, the key to looking (and feeling) loose is to always keep knees soft. Don't lock 'em.