The Core: From Development, Through Distortion, to a Potential Solution

I began working in outpatient physical therapy as an exercise physiologist back in 1996. At that time, I had no intentions of becoming a physical therapist and was busy trying to carve a niche in my profession as a strength and conditioning specialist. Back then, both the exercise science and physical therapy communities were running wild with this new form of training that would revolutionize the way we manage orthopedic conditions and enhance performance on the field. Like cave dwellers witnessing fire for the first time we all gathered around to learn of this phenomenon called "The Core."

Origins of Core Training

The idea of the spine having "pillars of stability" was proposed by Panjabi back in the early 1990's. The theory was that an integrated system of passive, active, and neuroregulatory factors work together to supply an appropriate amount of stiffness or mobility of the spine during ADL. A failure of one or more of these systems could contribute to an increased risk for many of the commons spinal pathologies we see in the clinic.

After this theoretical basis for spinal stability had been achieved, an avalanche of studies began to support Panjabi's pillars of stability theory. Many studies were based on surface EMG and began to reveal that spinal musculature, specifically the multifidi, transversus abdominus, and quadratus lumbora are integral in supplying the spine with the right combination of mobility and stiffness for effective movement.

This theory was subsequently supported by clinical data that many of these muscles are both histologically and electromyographically-challenged in patients with clinical spinal syndromes compared to healthy cohorts. We began to see consistent relationships between the dysfunction of specific muscles and clinical spinal syndromes and were building a solid foundation of basic and clinical sciences. By the end of the 1990's there seemed to be an established (but incomplete) theory on relationship between clinical spinal pathology, local muscle physiology, and central neuroregulation of these muscles.

Where have we gone wrong?

Simple: Words mean things. Clinical research seems to make a strong case for Panjabi's pillars of stability. However, "core training",as it came to be known, had tragic flaws all too common in our community: lack of a clear operational definition coupled with an overblown marketing appeal. A recent editorial in the Archives of Physical Medicine and Rehabilitation by Marc Sherry, PT, LAT, CSCS* and colleagues illustrates the problems we are having in the absence of a clear definition of "The core".

We are all over the place here. Some refer to the core in anatomic terms. Specific muscles on, near, or sometimes slightly distant to the lumbopelvic complex literally are the core. Others might refer to the core in a more abstract functional context. For example, we've all heard therapists say a patient lacks "core stability" or "core strength" as if these terms were synonymous. Furthermore we therapists often use equally nebulous terminology to describe how we manage this problem. We utilize "dynamic lumbar stabilization" activities or "core strengthening" exercises to help the patients "stabilize their core"...or whatever.

A Modest Proposal

As with many modern clinical issues, communication is likely at the root of both the problem and the solution. I propose gradually working toward a more unified definition of Panjabi's theory in the same spirit as Flynn and colleague's plea to unify our language of manual therapy. As a good friend of mine likes to say, it may be akin to "herding cats" in getting the PT community at large to embrace this kind of unity. However, for all the reasons we need to more clearly define our manual techniques, we may want to pass the same standards on to our exercise interventions.


Barr, K.P., Griggs, M., Cadby, T. (2005). Lumbar Stabilization. American Journal of Physical Medicine & Rehabilitation, 84(6), 473-480. DOI: 10.1097/01.phm.0000163709.70471.42

Barr, K.P., Griggs, M., Cadby, T. (2007). Lumbar Stabilization. American Journal of Physical Medicine & Rehabilitation, 86(1), 72-80. DOI: 10.1097/01.phm.0000250566.44629.a0

Sherry, M., Best, T., Heiderscheit, B. (2005). The Core: Where are we and where are we going?. Clinical Journal of Sports Medicine, 15(1), 1-2.