What gets you flat abs faster: Crunches or planks?

The question: What core exercise will score me a six-pack the soonest?

The expert: Cedric X. Bryant, Ph.D., chief science officer for the American Council on Exercise

The verdict:

When it comes to sculpting the perfect vanity muscles under your shirt, the crunch is still king.

In a new study commissioned by the American Council on Exercise, researchers from the University of Wisconsin, La Crosse placed electrodes on exercisers' abs and found that the crunch activated the rectus abdominis and external obliques—the muscles that recently launched Zac Efron to sex-symbol status—than either the front or side plank.

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What's more, the crunch activated those muscles more than the yoga boat pose, stability ball crunch, decline bench curl-up, captain's chair crunch, or bicycle crunch, and more than equipment including the Ab Circle Pro, Ab Roller, Ab Lounge, Perfect Sit-Up, Ab Coaster, Ab Rocket, Ab Wheel, and Ab Straps.

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Before you throwback to your high school gym routine, though, remember that you have internal ab muscles to tone, too. And while your deeper core muscles, like your transverse adbominus and internal obliques, don't ripple underneath your shirt quite the way your outermost muscles do (or at least will), strengthening them is vital to your fitness and physique, Bryant says.

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These muscles form a sort of internal (and totally masculine) corset that pulls in your gut while protecting your spine and back from injury. What's more, they serve as your body's power center, transferring energy between your upper and lower extremities to increase your power, performance, and, ipso facto, results.

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The bottom line: "To create the ideal ab routine, you need to incorporate both the crunch and plank," Bryant says. "There's no single exercise that trains every core muscle perfectly."

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