When it comes to the crunch...
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If there is one exercise that is the antithesis of Primal Fitness, it is the stomach crunch.

What I can’t understand, is why this ridiculous, ineffective and dangerous exercise simply refuses to die out?

I have been working in the fitness industry for the best part of a decade. Over that time I have learnt a lot, and changed my opinion on many things. All that time ago, however, when I still thought that whole grains were healthy and bacon was bad (dark times), there was more than ample evidence that stomach crunches were bad news, and I have been campaigning against them ever since.

When choosing which movements to incorporate in Primal Fitness classes, they have to satisfy a number of check lists:

1) Is it a natural movement?

2) Does is have a functional purpose?

3) Is it safe?

4) Is it fun/rewarding?

A good example of a Primal movement would be a box jump. Its a natural human movement, it has a functional purpose (you can jump up and onto things), although there is an element of risk (scraping shins etc), providing you train wisely and within your limits with good technique the movement itself is beneficial, and I personally love doing box jumps – Even if you might not class it as fun, achieving a new max is definitely rewarding.

Lets see what happens when we apply these questions to the crunch:

1) Is it a natural movement?

Not really. Although the body can move in this way, this does not mean it is supposed to do it repeatedly in a prone position. At no point in your life, or in the history of human evolution, has there ever been a need to lie on your back and repeatedly flex your spine.

2) Does is have a functional purpose?

The supposed function/purpose of stomach crunches are two fold – To build the ab muscles, and to burn abdominal fat.

When it comes to building muscle, rep range is very important. The optimum rep range for adding muscle mass is between 6-12 reps per set. Stomach crunches are simply far too easy to build muscle – Performing 50+ reps of crunches is effectively an aerobic workout which will not stimulate any muscle growth.

But maybe this is good? At least it will be burning fat, right? Unfortunately no. Firstly, you can’t spot reduce fat – Using you stomach muscles does not necessarily burn fat from the stomach, nor does working your glutes burn fat from your back side. You are just as likely to burn fat from your stomach by doing a leg or arm exercise, as you are from working your stomach muscles directly.  As the crunch is a very small range of motion, and isolates the abs, using just a small amount of muscle, it burns very few calories, and therefore very little fat. You could potentially burn a lot more belly fat by choosing a full body exercise that recruits a lot of muscle and has a big range of motion – Like box jumps for example! (Though of course if fat loss is your goal, diet is always the answer).

3) Is it safe?

Performing lots of stomach crunches is potentially very bad for your back. Different muscle groups have different functions. The muscle groups in the arms and legs are meant to produce movement – Jump, sprint, climb, throw, etc. The muscles of the core, however, are meant to resist movement, and transfer force from the lower body to the upper body and vice versa.

Think of the core muscles like the guy ropes around a tent – They are all supposed to be under equal tension holding the tent (in this case, your spine) upright and rigid. Think what would happen if you make the guy ropes on one side of the tent short and tight, and the ones on the other side long and stretched – You’re going to have a deformed and unstable tent. Performing lots of crunches causes dysfunction in the core muscles, leading to bad posture, with an overly curved spine.  This is made worse by the fact must of us sit in a crunched position at work all day too!

To make matters worse, the repeated flexion of the spine puts undue stress on the intervertebral disks – Leading back expert Dr Stuart McGill likens the spine to a credit card: It may start off as your flexible friend, but if you repeatedly bend it in half eventually it will break – In the case your back you could ultimately rupture or herniate a disk. Seriously bad news.

4) Is it fun/rewarding?

Well, everyone is different, but I personally cannot see the appeal! The reason your typical globo-gym is full of plasma TVs is because the dangerous and ineffective exercises they prescribe are also invariably highly tedious and unrewarding too.

So as you can see, under the Primal movement selection criteria, the stomach crunch is a fail on all counts. You can imagine my dissatisfaction (i.e. rage) when I saw that this was the image that had been selected to represent us to the masses.

I still can’t understand, however, why the exercise is still so popular? I can understand how the “healthy whole grain” myth proliferates, and vibrating platforms abound – There is money to be made – But who profits from the crunch?

I suppose there are the ab cradle, swiss and bosu ball manufacturers who may have something to gain, but in reality I don’t think its anything so sinister, its just a sad case of people, and even fitness professionals doing an exercise because they have always done it, and never stopping to think about why, and whether it is actually a good thing.

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