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Do You Understand Your Abs?

With summer in full swing, there’s been a lot of talk around Uxbridge about abs lately.   It seems everyone wants to lose a few inches off the waist, get a flat stomach or six-pack abs.

As a fitness coach, I could go on about diet and how spot reduction doesn’t work, but forgetting that for now – here’s the problem that Mike Robertson and I see:  Most folks “training” their abs are still caught up in outdated training methods, and not focused on what science has brought to light over the past 5-10 years.  Let’s take a quick look at the actual anatomy of your abs, as well as the various functions that your Rectus Abdominus (RA) provides.


The RA is a large, beaded muscle that runs from your xiphoid process and bottom of your rib cage to your pubic symphisis.  It’s interesting (and important) to note that instead of being one long, continuous muscle, the RA actually is broken up into several smaller sections.  But more on that later.

The RA has several well-defined roles, along with some lesser-known roles, too.  Let’s examine each.


The primary functions of your RA include:

–    Trunk flexion/Resisting Trunk Extension –    Posterior Pelvic Tilt –    Transmission of “hoop” stresses

Let’s look at each in a little bit more depth, as this is where the story starts to unfold.

Trunk Flexion

Any Uxbridge trainer or fitness enthusiast who knows anything can tell you the RA can promote flexion of the trunk.  This is why you’ve seen the ridiculous number of ab rollers, Bender balls, and other gimmicky guru crap being sold at 2 am in the morning for decades.

The idea, initially, was that sit-ups were the best to promote this flexion movement pattern.  Then, people started looking deeper and decided that sit-ups placed too much compressive loading on the back, or that they didn’t “isolate” the RA from the hip flexors.  Thus, crunches were deemed better for “isolating” the abs and keeping the back healthy. 

The problem, however, is that while your RA is capable of producing trunk flexion, the underlying anatomy leads us to believe that this role isn’t nearly as important s the fitness industry has given it credit for.  At the Chicago Perform Better Summit in 2007, world reknowned spinal biomechanist Dr. Stuart McGill went so far as to say that if your RA was really there for crunching and trunk flexion, instead of having the beaded sub-sections, you would have one long, continuous hamstring instead!

We also need to ask ourselves another question:  At what cost are we crunching?  This is where we have to examine the big picture.  Will trunk flexion help “bring out” our abs?  Maybe – but at what cost?  When we examine the big picture, we start to realize several things.

1 – Trunk flexion works to shorten our RA.  Doing so exerts a downward pull on our ribcage, effectively pulling us into an increased thoracic kyphosis or “slouched” upper body posture.  Not only is this aesthetically unattractive, but virtually useless to us as weight trainers, fitness enthusiasts or athletes.  By pulling our body into an increased kyphosis, we lose the ability to get our scapulae into the appropriate positions and increase the likelihood of shoulder and rotator cuff problems. 

2 – Research by McGill and others has shown that repetitive flexion/extension of the spine is injurious.  Our spine only has so many flexion/extension cycles in it; once we hit a certain threshold, we get injured!

Mike Boyle has a great analogy here – it’s like a credit card.  Bend a new credit card back and forth and, initially, it bounces back.  But if you continue to bend that card, you eventually start to see a white crack.  Continue to bend it back and forth, and over time that crack leads to a break.  Your spine is not much different.  And hey, maybe this is the reason that the Canadian Center of Activity and Aging identified spinal flexion as a movement pattern that should be contraindicated for those with osteoporosis – years ago!

Here’s another way to think about this – instead of thinking about promoting movement, start to think about how your muscles work to control or resist various movements as well.  In this case, your RA not only promotes trunk flexion, but it also works to resist trunk extension!  It’s not rocket science, but it’s a huge step forward in your thinking.  Far too often, we only think of how muscles work in an open-chain, textbook definition, instead of what they do in real life.

However, there might be some exceptions to this rule – I can think of a few high-end athletes who might need some judiciously included trunk flexion in their programming.  For most of the population, however, hopefully we can agree that crunching and trunk flexion movements probably aren’t in the best interest of our bodies. 

Posterior Pelvic Tilt

The second function of the RA is to promote posterior pelvic tilt, and/or to control pelvic alignment.  While many are focused on upper vs. lower RA, it only has one common nerve supply and therefore can’t be isolated into upper and lower sections. 

Many people assume that exercises like leg throws and ab wheel rollouts must hit their “lower” abs harder, because they get so sore following these exercises (especially when compared to crunches).  The primary difference, however, is that these movements emphasize the negative portion of the lift.  Eccentric exercise has been proven time and again to increase delayed onset muscle soreness (DOMS), so it’s not so much that you’re training different muscles as it is that you’re shifting the type of training stress.  Or it could just be that you’re doing something “new”, which is also virtually guaranteed to make you sore.  It’s not necessarily better, it’s just different.  But I’m getting a little off target here; I digress.

Transmission of Stresses and Force

The final piece of the puzzle is promoting or transmitting “hoop” stresses that are generated from the obliques.  The idea here is simple – instead of working to promote movements around the lumbar spine, the RA (along with the rest of the abdominal muscles) was primarily there to prevent movement and transmit forces!  Again, this was a huge shift in thinking.

So, in other words,  isometrically training the rectus abdominus is consistent with its anatomy and stabilizing function to enhance performance and power development in the hips and extremities.

Quite simply, stop moving and start stabilizing!  If you want to get the most out of your abdominal training, you’d be well served to focus on exercises that optimize pelvic alignment and train your body to stabilize the lumbar spine.  Not only will you stay healthier, but you’ll perform better as well.

And if you’re an Uxbridge athlete, you should be aware of this fundamental concept – the core doesn’t promote the power itself.  Instead, it transmits the power that the hips and thighs have generated.


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