Barre classes are hot, hot, hot right now. If you live in NYC or LA you can’t walk outside without tripping over a new ballet-inspired/barre fusion/dance-ilates studio, and the trend is spreading into cities all across the country.Not that we’re complaining. Barre classes are a breath of fresh air for many fitness aficianados who are sick to death of traditional workouts, exercise newbies who prefer low-impact activity, yoga- or Pilates-lovers looking to mix it up, or ex-dancers who’d rather die than go for a run.QUIZ: Are You Fitting In Enough Exercise?Barre and ballet-inspired classes take you through a series of exercise moves designed to target certain muscle groups with laser-like precision. Arms, abs (which in barre speak is called your core), glutes (read: butt) and thighs all get attention. The point is to increase your muscle control. You know how dancers can stretch one leg behind them in arabesque, and just freeze? Imagine you had ass muscles that could handle that.Rather than big, sweeping movements, expect to do tiny maneuvers that you’ll repeat so many times that you’ll think body parts might actually fall off. For instance, during the grueling thigh section, a typical move is to hold onto the ballet bar and sit back as if you are in an invisible chair. Then you pulse an inch up, then down, then up, then down. Simple but deadly.The repetitive movements fatigue the muscles, which forces them to adapt, AKA build new muscle fibers and get stronger.MORE: The Best Yoga Performance Socks & ShoesThese targeted exercises plus strategic stretching deliver a full-body workout, and most classes move quickly enough to get your heart rate up, making these classes a decent substitute for cardio workouts. Barre classes won’t give you the body of a professional ballerina (they have genetics and eight hours a day of dancing to thank for that) but for people who consistently go to class two to three times per week, the results are a toned, slimmer body, better posture and an increased feeling of grace.Check out our picks for the best classes and at-home DVDs out there, and let us know if you’ve found fitness success with any ballet-inspired classes.