A Model for Core Stability

What comes to mind when someone says the “core?” Many people think a 6 pack after performing hours of crunches. Others think it is low back and abdominal muscles working together for lifting objects. For some, the transversus abdominis jumps in their head. As our knowledge of human movement has progressed, it now seems more people are willing to consider the core the functional sum of many muscles. I personally like the model of the core as proposed by Mary Massery.1 In particular, the way it clearly describes the regional interdependence of the core. I have taken her “If You Can’t Breath, You Can’t Function” and “Advanced Pulmonary” courses and have really been able to apply it to various patient populations. Here is a quick breakdown of core stability that I find useful.

Essentially, the core runs from the neck to the pelvic floor. When pressure is adequately regulated through this system, core stability is created. The mechanical act of breathing is the major player in pressure control. The vocal folds at the top and the pelvic floor at the bottom are 2 valves that influence this pressure system. Thoracic and abdominal pressure are largely regulated by the diaphragm. However, the musculoskeletal system located between the neck and pelvic floor can also assist or even take over if needed.

Massery likens this pressure regulation to a soda can. When there is no breakdown in the system, our core resembles a closed soda can (very stable).  It is similar to an open soda can (limited stability) when there is a breakdown in the system like low back pain.  Try crushing a closed can, then crushing an open soda can to better see this. Dysfunctions of the core can occur outside of the abdomen and low back. Anything that could impair the mechanical act of breathing or pressure control in the core as described above. Tracheostomies, incontinence, constipation, COPD, and much more can disrupt this dynamic system.

I know for a quick overview that was a lot of information. In the future, I hope to expand more on this topic. Actually, I am taking courses on myofascial release for dysphagia and external treatments for pelvic floor dysfunction in the near future. By taking these two classes, I hope to pass on some new ways to look at treating the top and bottom of the core.

Hope this helps,



  1. Massery M. Multisystem Consequences of Impaired Breathing Mechanics and/or Postural Control.
    In: Frownfelter D, Dean E, eds. Cardiovascular and Pulmonary Physical Therapy Evidence and Practice, ed. 4. 4 ed. St. Louis, MO.: Elsevier Health Sciences; 2006:695-717.

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