Does Doing Crunches Actually Strengthen Your Core?

how crunches work
JGI/Tom Grill / Getty Images

Crunches or abdominal crunches work the rectus abdominis muscle in the midsection of your body. Ab curls may also engage the external or internal oblique muscles, especially when rotation is added to the movement. Abdominal crunches are an effective way to strengthen the front of your torso or core region of your body.

Do Crunches Work?

Abdominal muscles are one of the first areas many people are eager to work on as they begin to lose weight. Belly fat can be particularly difficult to get rid of and some people are prone to have more of it.

So do crunches work to whittle your waistline? It really depends on your goal. The only way to get rid of fat in your belly (or anywhere on your body) is with a healthy diet and cardiovascular exercise. Spot reducing, or trying to lose weight from an isolated area of your body, doesn't work.

But performing exercises to tone and strengthen the muscles in your abdominal area will help your stomach appear flatter once belly fat is reduced. But before we discuss toning your abs, we should take a closer look at your abdominal muscles.

What Muscles Do Crunches Work?

The area of the body commonly referred to as "the abs" is a combination of four muscles:

  • The rectus abdominis runs from your rib cage to pubic bone; the upper and lower halves can be worked separately
  • The internal and external obliques run along the sides of your body from your ribs to your hips along the front of your torso
  • The transversus abdominis is the deepest abdominal muscle, running horizontally across the torso

To flatten your abdominal area, you will need to work all four muscles on a regular basis. That means you do crunches or another variation of abdominal exercise two to three times a week. And of course, you need to reduce abdominal fat with diet and aerobic exercise as well if you want your results to show.

This may sound daunting, but keep in mind strong abs provide a benefit that goes beyond a flat belly. A strong core also promotes good posture, helps to alleviate lower back pain and can contribute to long-term health and well-being.

How to Do a Crunch

One of the best ab exercises for beginners is the traditional or classic crunch. This basic crunch exercise works the rectus abdominus, the most prominent of the four abdominal muscles. 

To do a classic crunch, lie on your back, bend your knees and put your feet flat on the floor. Clasp your hands loosely behind your head. Relax your back against the floor. Now, slowly curl your shoulders up from the floor to a 30-degree angle (approximately). Make sure you don’t pull up on your neck. Hold for a second and then lower. Repeat for two sets of 8 to 12 repetitions. As you get more fit, work up to three sets of 10 reps.

Form is especially important when you do a basic crunch exercise. But according to Sports Medicine expert Elizabeth Quinn, most people don't do crunches correctly. "Using good form when doing a crunch makes this a much more effective abdominal exercise," she says. "Proper technique not only impacts how effective the exercise is but doing crunches incorrectly can actually lead to back problems."

To keep your crunches in top form, remember these pointers:

  • Always exhale as you contract (bend) and inhale as you release (go back to starting position) during the crunch.
  • You should never pull on your neck when doing a crunch. If you can’t clasp your hands behind your head, you can cross them over your chest instead.
  • Always keep your chin off of your chest when doing a crunch. You can actually rest your fist under your chin to make sure that your chin doesn't drop too low. 
  • Move slowly and continuously as you do the crunch.

Crunch Exercise Variations

Of course, working your abs doesn't begin and end with the basic crunch. You can add crunch variations to challenge your muscles and get stronger, tighter abs.

A study by the American Council on Exercise (ACE) found that Captain's Chair crunches, the bicycle maneuver, and ball crunches were the top three most effective ab exercises. Some variations on the crunch, such as the Captain's Chair, require gym equipment. Others can be done at home, such as the ball crunch, which is performed with the aid of an exercise ball.

Variations on the crunch include:

Don't worry about investing in a gadget from television to get your "dream abs" flattened. The ACE study found that the Ab Roller, for example, was only slightly more effective than a traditional crunch. The Ab Rocker was shown to be up to 80% less effective than a traditional crunch.

Was this page helpful?