The word “CORE” (used in a fitness context) is one of my biggest pet peeves.

It became a big buzz word years ago.

Everyone needed to strengthen their “CORE”.

But, what exactly is your “CORE”?  Most people don’t know.  They know it refers to the middle of the body.  But, ask for specifics, and they don’t know.

Many who define it, define it differently – I have heard more variations on this definition than anything.  Ever.

Some say it is your rectus abdominus (“six-pack muscle”) and obliques.  Others define it as your entire trunk.  Still more use it to cover everything from the base of your neck down just below the hip joints.  My favorite are the people that point generally to their midsection, and say, “it’s your abs, right?”

So, being someone that likes to understand things, you can see where I struggle with this word.  Many people use it, but there’s no clear definition.

So, let me break down how I define it (in case you ever catch me using it…it doesn’t happen often, but it does happen).

I break it down into the inner core and outer core.

Inner core.

This includes the transversus abdominus, diaphragm, pelvic floor, and multifidi.  They lie deep in the torso, and their primary job is to help stabilize and protect the spine.  These muscles work together to elongate the spine and hold it still when appropriate, which ultimately keeps our intervertebral discs from getting damaged.  Those discs get smooshed from the pull of gravity, moving too far, moving poorly, poor posture, etc..  They are pretty tough cushions, but they can only take so much.  So, if they keep getting smooshed without relief, they start bulging and eventually herniate – which can press on a nerve and become very very painful.  Our inner core is designed to elongate the spine and unsmoosh the discs a bit.  It’s also there to help prevent smooshing from bad movement and bad posture.  It holds the spine still when the spine shouldn’t be moving (when lifting an arm, for instance), and it supports the spine in movement.  And it is active in proper posture so that there’s not undue pressure on the discs.  Also notice, the diaphragm is part of this – breathing is critical to good movement, good posture, and spinal health.

Outer core.

This includes the rectus abdominus and the obliques.  These muscles move the spine.  The rectus abdominus bends the spine forward (spinal flexion) and prevents the spine from bending too far backward (ok, kind of).  The obliques rotate and side bend the spine.  They also help stabilize the spine, but that is not their primary function (spinal stabilization is really quite complex because there are so many forces upon it, so I’m simplifying a bit).  Spinal movement keeps the discs hydrated and better able to absorb the forces upon them.

The big problem is that parts of our bodies don’t operate in a vacuum.  For instance, poor shoulder function can put undue pressure on the entire spine, and having tight hip flexors can inhibit hip movement and pull strongly on the lumbar spine.  So, people have tried to include other muscles that affect the spine or connect to the trunk into their definition of the “CORE”.  Unfortunately, our bodies function as one unit, so it’s a slippery slope.  You’d have to include everything in the “CORE” by their reasoning.

My definition of “CORE” is based on what I hear people (doctors and physical therapists included) trying to achieve by strengthening the “CORE”.

“CORE” strengthening is about keeping the central structure of the body – the spine – healthy and undamaged.

It’s about having a powerful body.

It’s about protecting our spinal cord and nerves.

It’s about being able to keep moving well for longer.

It’s about being healthy and without pain.