Captain Crunch

October 17, 2011

Walk into any gym and one of its most popular exercises will be performed in staggering numbers.  It’s some form of crunch.  Urban legend holds that you can add muscle on top of fat if you breathe different; you can target those lower abs by letting your legs hang off the bench; or you can look like an extra in “300” if you just get some burn going – anything less than 200 reps and you’re a sissy.  I genuinely appreciate why people are doing crunches.  There are many pressures to have a flat and toned belly.  However, I’m here to tell you that not only are hundreds of crunches an insignificant part of the look, they are probably hurting you.

First off, the typical crunch doesn’t really get much activation of your abdominal muscles.  In fact, Dr. Stuart McGill has measured the muscle activity of numerous forms of crunches and the largest contributing muscle groups are the quads and hip flexors1.  According to research from my colleague Bret Contreras, the pull-up activates the rectus abdominis (the six-pack) more than any form of crunch or sit-up; a great reason for guys and gals to do pull-ups.

Even if you correctly target the abs the six-pack battle is not won here.  These muscles are not physiologically prone to large amounts of growth.  Moreover, you still have to contend with that pesky layer of fat that sits over the muscles.  What really matters in seeing your abs is fat loss.  Those folks in the commercials who are totally ripped are not really “jacked” or “swole”; instead they are extremely lean.  Fat loss involves genetics and many things under your control such as high-intensity interval training, weight training, good rest, and restricting processed foods (especially sugar, caffeine and alcohol).  This is what old-school body-builders did before drugs clouded the scene.  Some experts rightly argue that hormonal imbalances will cause regional deposition of fat.  The situation is individualized and can’t be discussed in this context.  Suffice it to say spot reduction (targeting an area of aesthetic concern) is possible but will require a serious investment on your part.

So far the common behavior (sit-ups, twists, and a poor fat loss plan) is an innocent mistake…we could leave it at that.  But I’ve got more bad news.  An average crunch places at least 700 (!) pounds of compressive force on the spine2.  Twisting or adding weight only compounds the stress.  Crunching on a gym ball only increases range of motion and the pressure on your discs; it is not a safer alternative. Virtually every exercise performed with a rounded spine will harm your lower back. This includes sitting, too.  The icons of abs are everywhere and crunches have been promoted as a way to attain the “six-pack,” so it’s not your fault you thought to do crunches.  However, with the knowledge that crunches have not been shown to be beneficial, and potentially harmful, you now know to decrease their frequency or stop altogether.  There is plenty of good news, and we’ll get to that in the next two posts on the topic.  Specifically, we’ll discuss exercises that work the abdominals without causing harm and help you reach your goals.  Stay tuned!

By: Max Prokopy

Disclaimer:  No attempt has been made to promote one particular fitness gym or performer.  No financial benefit is associated with any of the above recommendations.


1.  McGill, S.  Ultimate Back Fitness and Performance. Stuart McGill Wabuno Publishers. 2004. Waterloo, Ontario.

2.  Axler CT, McGill SM.  Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge.  Med Sci Sports Exerc. 1997 Jun;29(6):804-11.

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