What to expect: A rock-star body! You'll tap weighted drumsticks on the floor and in the air for hundreds of reps in 45 minutes while you hold squats, lunges and crunches.
Know before you go: All that stick slamming can get loud. No one will make fun if you bring earplugs.
Your turn: Tell ab flab to beat it: Hold Boat pose as you drum the palms of both hands on the floor at the side of your body, twisting from right to left for one minute.
You don't have to be Jennifer Aniston to have a starworthy bod in Tinseltown. New workout joints debut daily, and cool trends keep gym-nistas coming back and looking like A-listers.
Los Angeles: 1,000-Calorie Ride
What to expect: To cycle until you reach your four-digit calorie-burning goal. Because your instructor wears a heart-rate monitor, she can tell the class when the tally ticks to 1,000—usually after upwards of 70 minutes. Post-ride, staffers pamper you with cold eucalyptus-scented towels and fresh fruit.
Know before you go: For every ride you buy, Cycle House's Take 1/ Give 2 program will donate enough money to feed two people through Feeding America.
Your turn: Think of this studio's mantra before every workout: "You have no idea what you're capable of."
Los Angeles: Contemporary
What to expect: A 90-minute lesson that will make you want to join the dance line on Smash! You'll learn modern, funky jazz and ballet steps, and before you begin, the instructor will identify a character for you to channel while you move. (Think "Vixen," "Siren," "Diva.")
Know before you go: This gym is a celebrity beacon. (Britney goes here to get her groove back.) So don't be surprised to box-step or grapevine next to dancing queens such as Christina or Janet.
Your turn: Watch videos of popular classes on the site, then let them inspire you to create your own choreography at home.
Los Angeles: Barry's Boot camp
What to expect: A muscle-shocking interval routine that leaves zero chance for daydreaming. For one hour, you'll switch between sprints on a treadmill (amping your speed to even 10 mph) and strength-building moves that use weights, a step and bands to tone every inch.
Know before you go: Each day has a specific workout (for example, Mondays are always Arms & Abs), so double-check the schedule to make sure it's what you want.
Your turn: A tip instructors yell over and over in class applies to your next heart-racing workout: "You can do anything for one minute!"