Planks vs. crunches. It’s the great ab debate that rages on among trainers and fitness buffs alike. So which is actually better? After consulting the American Council on Exercise’s muscle-activation studies and discussing them with Jessica Matthews, M.S., exercise science professor at Miramar College in San Diego, and senior advisor for health and fitness education for ACE, here’s the lowdown on what works, what doesn’t, and where science falls short.
1. Do crunches—the right way
The resounding ab winner in the muscle-activation studies is, in fact, the standard crunch. “Crunches aren’t this horrible villainized exercise that they’ve become over the years,” Matthews says. “When done correctly, they’re great for eliciting muscle activity in that part of the body.” The key words are “done correctly,” which Matthews describes as a full range of motion, engaging through the abdomen to lift the shoulders up off the ground. “You can have lots of variation in tempo, but if you find yourself lowering rapidly without control, try doing one count up and three counts down.” What doesn’t matter: Where you put your hands. The ACE study looked at both the cross-chest position and hands-behind-head and found no difference in ab muscle activation. However, if you have a tendency to interlace your fingers and yank on your head, cross-chest may be better for you, says Matthews.
2. Bicycle crunches are good, too
For activation of the external obliques, regular crunches don’t quite hit the mark. “The traditional crunch is a forward and back motion, great for the rectus abdominus but less so for the external obliques,” Matthews says. But bicycle crunches fit the bill, because those strong side-ab muscles both control and stabilize against the rotation of the torso. To get the most from your movements, again, you want to get those shoulder blades up off the ground, and think shoulder to knee rather than elbow to knee—the latter tends to cause more arm-winging and neck-yanking.
3. Visit the captain’s chair
That is, the apparatus (or those two straps) that allows you to hold yourself off the ground by your forearms, so you can use your abs to pull your knees up toward your chest. Even if done linearly with the legs coming straight up, the external obliques get a good workout as they need to stabilize the whole lower body. Make it even more effective by bringing the knees up to either side, suggests Matthews.
4. And do your planks, too
That brings us to planks. The ACE study looked at both front forearm planks and side planks in terms of muscle activation of the rectus abdominus and the external obliques. The news was… not good. So should you scrap ‘em? Matthews’ resounding reply: Nope. “There are many additional muscles that make up the core—the deeper muscles we can’t access with electrodes,” she says. “In terms of training the core in the way in which it works in everyday life, you need to use muscles like the TA [transverse abdominus], which stabilizes the spine. Planks do that.” However, she says, there’s plenty of room for improvement on the static plank. The idea of the plank is to train the core muscles to stabilize the spine against movement. Once you’ve mastered a solid 30-second static plank, add movement to it to make the core muscles work harder. “Try rocking back and forth on your toes and forearms,” Matthews suggests. “Or shift side to side, or do forearm circles.” No matter which plank you chose, be sure to brace your abs in (as if you’re about to get sucker-punched) and squeeze your glute muscles to keep your hips fully extended.
5. Stop trying to target your “lower” abs
Why? Because they don’t actually exist. The rectus abdominus is one muscle, top to bottom. Trying to work one portion and not another would be like trying to squat without bending your knees—it ain’t happening. The ACE tests further prove this, by showing no different activation in the “upper” abs versus the “lower” ones for any of the exercises tested.
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