How to Do Crunches: 5 Mistakes Everyone Makes

Research from the University of Wisconsin–La Crosse shows that the crunch activates the rectus abdominis and external obliques better than any other common core exercise. But that's granted you know how to do crunches the right way. "People think crunches are easy, so they rush through them with improper form," says Jacquelyn Brennan, CSCS, a personal trainer to collegiate and professional athletes, and co-founder of Mindfuel Wellness. "Then, they're unhappy with their results." The first step to a better return: Fix your form. Learn how to do crunches properly, and strengthen your core fast.

1. The problem: You crunch too high.

These are crunches, not sit-ups. When you crunch high, you take the emphasis off of your rectus abdominis and onto your hip flexors, says Brett Hoebel, creator of the 20 Minute Body and celebrity trainer on The Biggest Loser season 11.

The fix: Focus on bringing your ribs down to your belly button, he says. It will raise your chest a few inches off of the ground. That little motion is all you need to target your abs.

2. The problem: You use momentum.

"If you rush through your reps, you aren't going to get the same benefits you would if you slowed down," says Brennan. "You end up using momentum rather than strength, so you take your abs completely out of the equation." Even worse, it can put extra force on your joints and up your risk of back injury.

The fix: Keep your movements slow and controlled. At the end of each rep, pause with your back firmly against the floor. Reset before moving on to the next rep, she says.

3. The problem: You yank your neck.

"You don't want your hands and arms helping you do the crunch," Hoebel says. And you probably don't want to strain your neck, either.

The fix: Work on maintaining an apple-size space between your chin and chest throughout the entire movement, Brennan says. If you still find yourself yanking on your neck, try crossing your arms over your chest or placing your fingertips around your ears. Point your elbows forward or, if you want to make the move more challenging, point your elbows directly out to either side.

4. The problem: You relax on the way down.

"A lot of people will work hard on the way up and then relax on the way down," Hoebel says. "If you do, you're skipping out on half of the work—and benefits."

The fix: Squeeze your abs to lift yourself off of the floor and, on the way down, just keep squeezing, he says. Focus on using your abdominal muscles to slowly lower yourself, rather than drop, to the floor.

5. The problem: You hold your breath.

Deprive your body of oxygen and your crunches are going to get a lot worse, Brennan says.

The fix: Exhale on the way up and you'll automatically breathe in on the way down, she says. Bonus: If you forcefully exhale during your crunch's contraction, you'll also activate your deeper abdominal muscles during the move.

The 3 Worst Ab Exercises of All Time

You don't go to the gym wanting to waste your time or throw out your back. But if you're cranking out these ab exercises, that could be exactly what you're risking. Here, three ab exercises to stop—stat.

Sit-Ups

As far as ab exercises go, this used to be the one and only. Thing is, after you raise your back off of the floor a few inches, you aren't doing much for your core. "The abdominals' optimal range of motion is relatively short," says Cedric X. Bryant, PhD, chief science officer for the American Council on Exercise. "Sit-ups take you past this range, and that extra motion doesn't do much for your abdominal muscles."

Worse, that extra motion can wreck your back. A traditional sit-up exceeds the National Institute for Occupational Health and Safety's recommended limits for lower-back compression. Translation: Over time, sit-ups increase the risk and prevalence of lower-back disorders. When you flex your spine—bending it forward over and over again—and compress it under your torso's weight, you risk bulging discs, says Stuart M. McGill, PhD, director of the spine biomechanics laboratory at the University of Waterloo. 

Leg Throws

You know the exercise in which you lie on your back with your legs in the air, and a partner pushes your legs down and to both sides? "Eliminate it from your exercise vocabulary," Bryant says. While most people perform the movement to tone their lower abs (which Bryant notes work together, not separately, from the upper abs), the exercise puts a lot of stress on the lumbar spine. If you have lower-back problems, or have had them in the past, they can cause immediate pain. Even if lower-back pain isn't an issue now, the movement can cause chronic pain and injury over time, he says. With four out of five people complaining of lower-back pain at some point in their lives, according to the American Chiropractic Association, do you really want to increase your odds?

Ab Circle Pro

While you never need a piece of equipment to effectively work your core, some as-seen-on-TV products are worth giving a go. The Ab Circle Pro? Not so much, at least according to a recent study from the American Council on Exercise. It may be that the equipment's design helps you complete the exercise's movements by taking the brunt of the work off of your abs, says Bryant. Did we mention that the Federal Trade Commission recently fined the manufacturer of the Ab Circle Pro $9.3 million for false advertising? (It claimed to help people lose up to 10 pounds in just two weeks.) We can't fault the equipment for not spurring weight loss—there's no such thing as spot-reducing fat, after all—but claiming it does? Not cool. You're better off saving your money and sticking with classic crunches, says the study.