Don’t Sell Your Abdominal Training Short by Doing Only Sit-Ups and Crunches

Sit-ups and crunches

When most people think about ab workouts, they immediately think they should crank out hundreds of crunches. But is that the best approach? While this exercise does work your abs, it also puts stress on the back and neck. In fact, crunches can put so much pressure on your spine that they can cause herniated disks or bulging disks if you’re predisposed or do them incorrectly. They’re also overhyped from a strength-building standpoint and you’ll soon out why.

Your abdominal muscles are made up of these muscles:

Rectus abdominis muscles

The rectus abdominis consists of two superficial muscles that run vertically from your pubis to the xiphoid process and ribs.  Developing these muscles is what gives you a “six-pack,” but to see that six-pack, you must shed the fat that covers your rectus abdominis muscles to reveal the striations.

External obliques

The external obliques are the outermost side muscles in your pelvis. They run diagonally down your pelvis on each side and help you bend to the side and twist your body.

Internal obliques

The internal obliques run in the same direction as the external obliques but lie underneath. They also help you bend sideways and rotate your body.

Transversus abdominis

These are the deepest muscles in the abdominal region. Although they’re covered by the rectus abdominis muscles, they have an important function. The transversus abdominis helps increase pressure in your abdominal cavity when you strain or cough. When this muscle is strong, it also pulls in your midsection like a corset.

For aesthetic purposes, it’s your rectus abdominis muscles you need to strengthen and hypertrophy for six-pack abs. But you must also train your obliques and transverse abdominis too for balanced ab development.

Why Sit-Ups and Crunches Aren’t the Best Exercises for Ab Development

When you do a sit-up or crunch, you might think you’re working your abdominal muscles, but when you sit up, another group of muscles does most of the work. These muscles are your hip flexors, particularly a muscle called the iliopsoas. The iliopsoas is made up of two muscles: the psoas major and the iliacus. These are the muscles you’re targeting. So, sit-ups and crunches train the wrong muscles!

Another Reason Not to Do Sit-Ups

As Harvard Health points out, when you do a sit-up, you press your curved spine into the floor. As you do the movement, your hip flexors, which are doing most of the work, pull on your spine. This pulling action can strain your lower back. Therefore, sit-ups are hard on your back, and they develop your hip flexors more than your abdominal muscles. Most people already have tight hip flexors, and sit-ups can worsen the tightness.

To build abdominal strength and definition, choose exercises that target your ab muscles and limit the activity of your hip flexors. Any exercise where you flex forward at the waist uses your hip flexors more than your abs, so crunches target your hip flexors too. The faster you do sit-ups and ab crunches, the more it tightens your hip flexors. You won’t get the ab definition you’re looking for, and tighter hip flexors will negatively affect your posture.

Alternatives to Sit-Ups and Crunches

If sit-ups and crunches aren’t the answer, what is? There are three main approaches for targeting your abdominal muscles more and your hip flexors less. Let’s look at each one.

Reduce Your Range-of-Motion

If you insist on doing ab crunches, reduce the role your hip flexors play by limiting the range of motion you use when you crunch. The best way to do this is to only lift your head high enough when you crunch to bring your head and shoulders off the floor. Once you lift your head higher than that, your hip flexors take over.

Focus More on Other Compound Exercises

Compound exercises, like deadlifts, squats, and push-ups, also work your abdominal muscles. Plus, these exercises are more effective than sit-ups and crunches for burning belly fat. Sit-ups and crunches are worthless for burning calories and fat and many people do them believing they can spot reduce that belly bulge. It’s not going to happen!  Focus your training time on exercises that work multiple muscle groups and force your abdominal muscles to stabilize.

Make Friends with Planks

Planks are one of the safest ways to strengthen your core muscles. Unlike sit-ups and curls, planks are an isometric movement that doesn’t require spinal flexion, making them safer for your back and spine. Planks activate abdominal and core muscles without placing high compressive forces on the vertebrae in the lower back.

They’re effective too. According to Physiopedia.com, planks work all four abdominal muscle layers: rectus abdominis, external obliques, internal obliques, and transversus abdominis.  You can target your obliques even more by including side planks in your abdominal training routine.

The Bottom Line

When you do planks and sit-ups, you’re working your hip flexors harder than your abdominal muscles. Plus, sit-ups and ab curls mainly work your superficial rectus abdominis muscles and do less for your obliques and transversus abdominis, Planks work all these muscle groups. You’ll get a better-balanced workout if you devote some of your ab training time to planks and do a variety of compound strength movements that force your ab muscles to stabilize.

Don’t neglect nutrition either. The limiting factor for developing abdominal definition, particularly for women, is a thick layer of tummy fat. Good nutrition is even more important than exercise for bringing your body fat percentage down and revealing those ab muscles. Exercise and nutrition are the ultimate in synergy; focus on both.


  • Health.Harvard.edu. “Want a stronger core? Skip the sit-ups”
  • “Plank exercise – Physiopedia.” physio-pedia.com/Plank_exercise.
  • Do YC, Yoo WG. Comparison of the thicknesses of the transversus abdominis and internal abdominal obliques during plank exercises on different support surfaces. Journal of physical therapy science. 2015;27(1):169-70.
  • “Core stability – Physiopedia.” physio-pedia.com/Corestability.
  • “Why Crunches & Situp Are Bad For Your Back.” 27 Feb. 2007, https://www.menshealth.com/fitness/a19541566/why-crunches-situp-are-bad-for-your-back/.
  • Contreras, Bret MA, CSCS1; Schoenfeld, Brad MSc, CSCS2 To Crunch or Not to Crunch: An Evidence-Based Examination of Spinal Flexion Exercises, Their Potential Risks, and Their Applicability to Program Design, Strength and Conditioning Journal: August 2011 – Volume 33 – Issue 4 – p 8-18. doi: 10.1519/SSC.0b013e3182259d05

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Abdominal Training: Why Less Ab Work is More

Are Planks Better Than Crunches for Abdominal Development?

Abdominal Training: How Often Should You Train Your Abs?

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