Baby Got Back- The Posterior Core and Anti-Flexion

As we move through our journey exploring core function and training, we come to another misunderstood topic- the muscles of the lower back.  We’ve already delved into the basics of core function and we’ve explored anti-extension, one of the 4 main components of core stability. Today we will look at the muscles that directly oppose the muscles of anti-extension.  Your anti-extension muscles are found almost entirely on the front side of your body and consist mainly of the Rectus Abdominis (RA), Transverse abdominis (TVA) and the Internal and External Obliques.  These muscles resist trunk extension, and we saw an example of them in use when we performed the partner drill where you and a partner face each other with extended arms and try to push each other over.

Anti-Flexion is the functional opposite of Anti-Extension.  The muscles involved with anti-flexion work to keep the spine neutral when there is a force- such as gravity, a barbell, or somebody pushing you from behind- acting to round your spine forward.  As you will see in the picture below, anti-extension and anti-flexion muscles cooperate to keep your body as close to neutral as possible as often as possible.

What muscles are involved with Anti-Flexion?

Lumbar-Extension-Muscles muscles-of-the-core-diagram

We will talk about the powerful muscles of the hip such as the gluteus maximus in a later post, and will focus on the oblique muscles when we cover our lateral core anatomy.  To get a basic understanding of the anti-flexors, we will narrow our focus down to the Erector Spinae and the multifundus.

The Erector Spinae (ES)

The erector spinae is aptly named as it is one of the primary muscles responsible for maintaining an erect spine.  It is a long, thin muscle which has attachments from the back of the head all the way down to the top of the hips.  The ES is composed largely of Type 1 muscle fibers.  Who cares?  Well, Type 1 muscle fibers are known to be very good at maintaining long duration, low force, and slow muscle contractions while not being very good at producing large amounts of force over a short period of time.  This means that Type 1 muscle fibers are made to work often, pretty much all day long, but are not meant to be creating a bunch of movement on their own.  We’ll see why this matters when we get to the exercise portion of this post.

The Multifundus

The multifundus is another muscle of the lower back which provides support and stability to the spine.  It is similar to the ES in that it is made up largely of Type 1 muscle fibers and is a long, thin muscle which spans most of the length of the spine.  Both the ES and the Multifundus have a very strong connection to the Central Nervous System and are therefore readily available for activation without much thought.

Stop Doing This:


Superman, traditional hyperextensions, or any other movement which prioritizes LUMBAR extension over HIP extension. When people ask me whether or not I think they should do a particular popular exercise,  the reasoning behind my answer usually comes down to whether or not I think that exercise gives the individual an appropriate amount of bang for their buck or if there is another, safer, exercise which more completely accomplishes what they’re trying to do.  Because of this reasoning, there are not many exercises that I feel are totally worthless or that I completely discourage people from doing.  The superman is a rare exception.  None of my clients do this exercise and while I am always open to a reasonable argument, I don’t forsee my opinion on this one changing.  McGill’s research shows that the superman exercise imposes somewhere around 1350 pounds of compression force on the spine, all while performing an action that the muscles of the lower back are NOT MEANT TO PERFORM.  This exercise asks the ES, Multifundus and others to repeatedly contract/relax and take the lumbar spine well past a neutral alignment.  Remember earlier when we talked about their appropriate function?  To resist flexion?  Yeah, the superman isn’t doing that.

Traditional hyperextensions performed with the feet and legs locked and the trunk and upper body free are dangerous for similar reasons- excessive compression forces and very little bang for the buck.  I do not completely discourage this one simply because I know people who are strong enough and body-aware-enough to actually do this movement without extending their lumbar spine…but when I say “I know people” I really mean I know one or two people who are good enough to do this for reps and sets.  For most people, this is not even a remote possibility and as such the exercise becomes dangerous and rather ineffective.  That’s why it falls onto this list, though I will not go as far as I did with Supermans and say nobody should ever try it.  I view reverse hyperextensions, performed with the legs free and the trunk and upper body supported to be a completely different exercise from the traditional hyper.  They are much easier to do safely, and target the large muscles of the hips, which are meant to create a great deal of force, rather than the spinal erectors, which are not.

Start Doing This:


Goblet squats. Front Squats. Deadlifts.  You’re going to find these exercises in just about every good training program because they’re awesome for developing strength and power of the lower body.  What often gets missed though is their ability to strengthen the lower back muscles.  Taking the Goblet Squat (pictured above) as an example, the weight is trying to pull the lifter forward, into flexion.  As long as the weight is appropriate for the individual, the lower back muscles reflexively activate to MAINTAIN a neutral spine.  They don’t extend the spine, they don’t jack the spine into positions it doesn’t like.  They simply keep it upright, just like they’re supposed to.

This “anti-flexion” force is not limited just to goblet squats.  How about a bent over row, as pictured below:

bent row

You can replace the dumbbells with a bar, a cable, a band, or whatever you want.  The resistance is trying to pull him into flexion, and the muscles of his lower back are acting to resist that flexion.

Just about any exercise which is front-loaded, meaning the weight is set out in front of the individual trying to lift it, exerts a flexion force which the body must react to in order to keep the spine neutral.  And the interesting thing with a lot of these exercises is that heavier loads tend to be better than lighter loads.  When a goblet squat, front squat, or deadlift is excessively light, the body really does not have to react to much and therefore technique gets sloppy.  When the load is heavy enough, your body is forced to counteract the load pulling forward to keep the spine neutral.  This is exactly what we’re looking for.  That’s the beauty of a well-designed training program.  If you’re doing the exercises you should be (deadlifts, front-loaded squats, etc.), then you don’t actually need to spend extra time training the posterior core.

Bottom line: Keep your spine neutral and lift weights that are heavy enough to create a reflexive stabilization technique in your core musculature…oh, and stop doing the superman.

Thanks for reading!



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