Our current definition of the Core is well…ill-defined. I know I have beaten this drum before, but in magazine articles, blogs, internet resources, even research articles, different muscles are included in the “Core” depending on who you read. I even hesitate to use the word because it means something different to each rehab practitioner, and fitness professional (or client) I talk with. Each of us thinks we are doing “Core” work with our patients and clients, but how can we be sure if our starting definitions are so vastly different.

Do we simply agree to disagree? Does this serve the people in our care? Or could we all take a step back and reconsider our understanding of the Core. I will take the first kick at the can on a new perspective of the Core and how to train it.

No matter which muscles we include in our definition, I think we can all agree on the BASIC purpose ofthe Core, which is to create a strong postural center and maintain central postural control within movements. Our physical center must be a stable, controlled anchor so that muscles that perform movements have something sturdy to pull against. This reduces stresses on spinal and pelvic joints, rather than have them yanked about by exterior forces. Also, the prepared postural center sets the body up for better performance/efficiency of the shoulders and hips.

However, HOW the Core achieves this ultimate purpose is where the water gets muddy.

It is easy to understand the inclusion of large postural muscles in a definition of Core. If the ultimate purpose is a stable, controlled postural center, then muscles that assist with posture make sense. So we can throw in Lats, Obliques, Rectus Abdominis, Erector Spinae, Glutes, etc. (often referred to as the outer Core). Looking at the purpose of the Core, these muscles DO promote ongoing postural control during physical action, but they do not activate first to create a central stable anchor prior to movement to insure control and improved performance. They can become those naughty external yanks on an un-prepared, unstable spine and pelvis.

In fact, we have multiple studies that have shown that in a simple arm movement the four muscles often referred to as the inner Core unit – Diaphragm, Transversus Abdominis, Pelvic Floor, and Multifidus –  activate before the shoulder muscles that create the movement. These four are the only muscles in the trunk that have the unique capacity to create preparatory or anticipatory contractions in a consistent way to control the center before movement begins. In the same studies, the other postural muscles or outer Core reacted in a different pattern depending on which direction the arm was moved, and they switched on after the inner Core components.  Meaning the outer Core also relied on the inner Core to set up a sturdy anchor, so they could do their job of  reactive postural adjustments within the arm movement. The action of both sets of Core muscles are intertwined for the achievement of efficient, effective movements.

So, can this lead us to an inclusive definition for the Core that is win-win for all the Core camps? How’s about the classifying things as the Anticipatory Core and Reactive Core*.  Both groups of muscles need to be trained in order to create a strong postural center and postural control within ongoing movement patterns. However, because they have different roles in achieving that purpose we must train them differently, but in relationship to one another in order to maximize patient and client outcomes.

Core camps unite! Do your Core training programs ensure the Anticipatory and Reactive Core work together within each exercise? Is a plank a true Core exercise if the patient/client holds their breath to create an anticipatory stabilization, so they can pull it off? Is exercise on the stability ball Core work if clients are seated in a hunch reducing reactive postural muscle function?

I have now officially kicked the can, your turn! Please weigh in below.

*I must give credit for these terms to Carolina Stock, OT. She put a name to the concepts of inner and outer Core interplay in a conversation we had at the Core Restoration in Kids class I taught a few weeks ago. I loved it so much, it inspired a blog!