You’ve seen them before on your gym’s class list: 30-minute-long, must-be-intense classes with names like “Ab Lab,” “Absolution,” and, most tantalizingly, “Ass and Abs.” Like late-night fitness infomercials, they promise to whittle your waist, improve your balance and posture, and flatten your stomach. All of which sounds like something more appropriate for women, so you keep scanning the schedule...Well, how wrong you are. 

These are core classes; and while many promise to make your six-pack pop, that’s just a surface look at what they’re all about. “Most people think core is an ab class, where you’re just doing crunches,” says Nyree Brown, a group fitness instructor at Equinox and a Brooklyn-based independent personal trainer. “Your core isn’t just that six-pack. It’s all the muscles that surround and support your spine,” including the transverse abdominis, internal obliques, multifidus, spinal erectors, lats, glutes, and traps. Collectively, they’re responsible for your posture and are the basis of your strength and power in sports and in the weight room. 

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How to Choose Your Core Session

Generally speaking, there are two common core-class styles: high-energy “washboard abs” versions, where the majority of time is spent on dynamic exercises like crunches, situps, leg lifts, and rotational exercises like Russian twists and woodchoppers; and more mellow, Pilates-style mat classes that focus on static holds like planks, Supermans, and glute bridges, but spice them up with focused pulses that work deep-down muscles. Neither is objectively better—both will work your abs to exhaustion and, if taught correctly, give you a solid workout—so finding the right one is more about preference. 

In her experience, guys tend to gravitate toward the more dynamic classes, Brown says. “They aren’t as quick to do a low leg raise and hold as they are to do some sort of medicine ball exercise, because it looks harder—and cooler.” She has a point. 

To pick the right class, then, she suggests reading the description: Whereas kettlebells, medicine balls, and crunches are giveaways of a dynamic class, Pilates and planks scream static. (Though, whatever your preference, it’s not a bad idea to mix it up occasionally.)

When it comes to choosing an instructor, there are two guidelines. First, you want someone who takes the class beyond its “Athletic Abs” marketing gimmick and builds a balanced workout around all the core muscles. Second, you want someone who’s constantly moving around the room, correcting students’ alignment and form. “Be sure your instructor is as engaged as possible,” Brown advises. 

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Don't Be a Douchebag 

Don’t go rogue. “When everyone in the room is doing a Russian twist, please don’t be planking,” Brown says— it throws off the class’s energy. “It’s the absolute worst! This isn’t a one-on-one session, and it’s not your own thing, It’s a class.”

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Attack Your Abs Right

1) Know if You’re in the Wrong Place.

The whole point of a core class is to hit the core from every conceivable angle, says Brown, using “planks, spinal flexion, crunches, reverse crunches, situps, obliques with rotational exercises and bicycles, and, finally, erectors with some Supermans.” If it doesn’t do that, you need to find a new class.

2) Speak Up.

If an exercise feels uncomfortable, especially in your lower body, tell the instructor, who should be able to offer a modification so you’re not risking injury.

3) Slow Down.

It’s critical to perform dynamic exercises at a slow, steady pace, focusing on the target muscle through the entire range of motion. This is especially important when you start to get tired and other muscles try to make up for your fatigue. 

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Core Dos and Don'ts

Do: Let the instructor know ahead of time if you have any injuries, particularly to the lower back. That way he or she can modify exercises to suit you or, depending on the severity of your problem, send you away. In either case, your back will thank you. 

Don’t: Wear the same workout clothes you’ve been rocking for a week. “You don’t want to be the smelly one in the room,” says certified fitness trainer Donovan Green, author of No Excuses Fitness. “It’s embarrassing, and it makes your classmates uncomfortable.”

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