Core Stability Model

Core Stability From the Inside Out

The core stabilization concept keeps being a hot topic for discussions. After more than a decade of core-training frenzy there is still very little evidence that core-training actually produces any positive effects. There is no universally accepted definition of what the make-up and function of the core is.

It all started with the Transversus Abdominis and the abdominal hollowing theory, where people were instructed to pull the belly-button in towards the spine when exercising. It has since been shown that abdominal bracing (tensing the abdominal wall as if preparing for being punched in the stomach) is superior to abdominal hollowing in regards to providing stability for the lumbar spine. Abdominal bracing is good, but it is still approaching the core from the outside in. The abdominal wall is the focus of the training. Real core activation has to come from the inside out.

Definition of Core

Core Stability Model

When looking up “core” in a dictionary we get descriptions like: centre, nucleus, middle, heart and interior.

If someone refers to the core of our planet they mean the absolute centre.  When people train their core they concentrate on the outer layers of the wall equal to the crust and the mantle.

People have to stop treating the core as a hollow tube and learn how to pressurize the “centre” of the tube instead of just tensing the walls.

Core Function

How do we pressurize the “centre”?

Intra-abdominal PressureThe diaphragm contracts and pushes down into the abdominal cavity, which combined with the resistance created by the pelvic floor, and an eccentric contraction of the entire abdominal wall, increases the pressure in front of the spine. The pressure from the front is counteracted by contraction of the lumbar extensor muscles and the spine is fully stabilized.  Without proper diaphragm contraction the increased  IAP will not reach all the way down to the lower lumbar spine, where the loading is most prominent.


The diaphragm is the key component to core stability. The diaphragm has to contract first and then the abdominal wall and not the other way around. A too early or too strong contraction of the abdominal wall prevents the diaphragm from descending properly and is therefore counterproductive in stabilizing the spine.

At this point I would like to present the results of two interesting MRI studies of the diaphragm by Professor Kolar and colleagues that demonstrated that the diaphragm has dual functions of respiration and stabilization.

The first study (1) demonstrated that the diaphragm has a postural function that can be voluntarily controlled and is independent upon breathing.

The second study (2) showed that the diaphragm can performed its dual functions of stabilization and respiration simultaneously. The diaphragm can perform the breathing task at a lowered position ensuring that the stabilizing pressure is maintained throughout the breathing cycles. There is a close relationship between the diaphragm and Transversus Abdominis which contributes to the respiratory and postural control.

These two studies pointed out that the activity of the diaphragm during stabilization varies greatly amongst individuals, which supports Kolar’s clinical evidence that individuals with limited capability to contract the diaphragm for stabilization have a higher risk of developing back-pain.  The simultaneous activation of the diaphragm’s dual functions is the key to proper core stabilization

It is interesting to note that in the study by Hodges and colleagues which started the core craze, it showed that not only the transversus abdominis but also the diaphragm was activated to stabilize the trunk prior to any limb movement. The transversus got all the attention and turned into the core super-star while the diaphragm got ignored.

Respiratory function of the diaphragm

During inspiration the diaphragm contracts and pushes down into the abdominal cavity which decreases the pressure in the thoracic cavity and the lungs fill up with air.


The diaphragm participates in all breathing patterns whether they are ideal or dysfunctional. You cannot avoid using the diaphragm when breathing even if you try, unless there is a medical condition preventing the diaphragm from contracting. The commonly used instruction “breathe with the diaphragm“, has no value.  Chest breathing and straight belly-breathing, where only the posterior part of the diaphragm pushes downwards, are two commonly observed dysfunctional breathing patterns, which reduce both the respiratory capacity and core stabilization. In ideal diaphragm contraction the entire diaphragm pushes down into the abdominal cavity and can be observed by an expansion of the lower ribcage and the abdominal wall in all directions.

Assessing diaphragm function

Breathing AssessmentThe diaphragm’s respiratory function can be assessed sitting or lying on the back. Holding the fingers at the lower ribcage, an examiner can feel for a lateral expansion of the ribcage and activation of the postero-lateral parts of the abdominal wall.  An upward or inward movement of the ribcage is a sign of dysfunctional breathing.

Next, the subject’s ability to pressurize all the way down to the lower part of the abdominal cavity when breathing is assessed, both in laying and sitting (holding the ribcage down assists the activation) .

Proper Breathing

After that, the postural function of the diaphragm is assessed. Instruct the individual to pressurize all the way down to the bottom of the abdomen while holding their breath. The instructor should be able to feel the pressure against a hand placed at the lower abdomen.

And finally, get the person to breathe all the way down to the lower abdomen and then maintain that pressure while going through normal breathing cycles. The diaphragm is now performing its breathing function at a lower position. This is real core stabilization.

Each of these steps should be properly activated and the testing positions are excellent to use as entry-level exercises. A resistance band can be strapped around the ribcage or the lower abdomen to pressurize against. It is worth spending a fair amount of time ensuring proper activation of the core before progressing to other exercises.

Here is a video, explaining core activation from the inside out:

Once proper activation of the core is achieved, only the individual’s imagination limits the exercise progression. Planks, bird-dogs, dead-bugs would be reasonable next steps. Uni-lateral work is an inventive way of keep challenging the core.

Frequently we see discussions regarding whether to perform core-exercises before or after other exercises. After reading this I hope everybody can see that once the diaphragm is properly activated the core will be trained in all exercises and activities. Proper core-activation is fundamental and should be part of everything we do.

The ability of the core to stabilize the spine and torso is the limiting factor in all exercises. Pay close attention to the signs of proper core activation.


Abdominal Wall

My favourite method of determining if the core is activated is to observe the lower lateral abdominal wall.  If there are concavities the core is not properly activated. Concavities indicate a Rectus Abdominis dominant pattern.

The contour of the abdominal wall should take on a balanced, slightly rounded appearance which should be maintained throughout performing the exercise with normal respiration.

Some individuals cannot activate the diaphragm properly by themselves and I would recommend they seek assistance from a DNS or Postural Restoration Institute trained Practitioner. Practicing with faulty patterns will only reinforce the dysfunction.

Core-stabilization has to come from the inside out and is controlled via the diaphragm. I recommend anyone who is interested in improving their performance and preventing low back pain to spend the required time to properly activate the core. It is really worth it. I have had experienced Strength athletes achieve new PB’s straight after we have activated their core.



1-   Kolar P, Neuwirth J, Sanda J, Suchanek V, Svata Z, Pivec M. Analysis of diaphragm movement during tidal breathing and during its activation while breath holding using MRI synchronized with spirometry. Physiol Res 58:383-392, 2009

2-   Kolar P, Sulc J, Kyncl M, Sanda J, Neuwirth J, Bokarius AV, Kriz J, Kobesova A. Stabilizing function of the diaphragm: dynamic MRI and synchronized spirometric assessment. J Applied Physiol Aug 2010


About the author:

Hans LindgrenHans Lindgren is a Doctor of Chiropractic and DNS Practitioner in Brisbane, Australia.  He has a special interest in Functional Stabilization, Rehabilitation and Sports-Performance. Hans runs courses about these topics and also writes a blog on

29 replies
  1. Jennifer Houghton
    Jennifer Houghton says:

    Excellent information, thanks for sharing. Its great to know that the breath work practices I’ve been teaching in yoga and Pilates classes (different from what is usually taught) have scientific backing. I let go of the ‘abs of steel’ mindset a long time ago and no longer have any back pain myself.

  2. Daniel Leaver
    Daniel Leaver says:

    Excellent article! Are there any exercises that you recommend for strengthening the diaphragm or for enabling it’s full ROM? Will an under-activated be tight and weak? Can someone with a very strong diaphragm damage the internal organs of the abdomen? What role does the pelvic floor play in core stability?

    edit: for proper core stability, one would need to push his diaphragm all the way down, and then pull the abs in?

  3. Cat Woods
    Cat Woods says:

    Hi Mike – as a group fitness instructor, are there some simple ways to cue this deep breath and contraction of the diaphragm?

    • mikereinold
      mikereinold says:

      I try to focus on them bracing their sides, that tends to cause the entire core to brace. You can also try a tactile cue on their side and have them push your finger out.

  4. Moses Bernard, DC, CSCS
    Moses Bernard, DC, CSCS says:

    This is the best description of diaphragmatic function I have ever seen. It is accessible to the layman, but most rehab professionals could learn from this. I am a chiropractor with DNS training, and I refer ALL my patients to this article. Thanks, and keep up the good work!

  5. Jacob
    Jacob says:

    Great article. Question though: How often should one be keeping the diaphragm in this lowered position while keeping pressure in the abdomen? Is this something done during all waking hours, to one extent or another? I definitely feel the difference/advantage between a “pressurized” core when squatting, but what about just during standing,walking and running?


  6. Karl
    Karl says:

    There’s a Dns Chiropractor in elk Grove California His name is Dr Brett lemere. He’s Really good and know so much about this type Of rehabilitation. He’s teaches classes and every fall goes back to Prague where he learns new information that they school had learn about DNS chiropractic.

  7. Adam
    Adam says:

    Hi There,

    Thanks for posting this article.

    Are there any layman’s resources available to better understand breathing as it relates to athletic performance and core stability? A resource with specific breathing exercises would be helpful.

    Thank again!

  8. Bob Schroedter
    Bob Schroedter says:

    Thanks for your contribution to this topic. Can you please provide a citation for the Hodges article you referenced?

    The contribution of the diaphragm in creating a pressurized center is not to be understated, but I think that discussion of stability coming from the core also should also not underestimate the contribution of the other components of the core cylinder (not tube), namely the pelvic floor. If IAP is to be maintained relatively constant during exertion the synchronous use of PF and DIA should also be assessed and trained for.

    • Hans Lindgren
      Hans Lindgren says:

      Hello Bob,
      Thank you for your comment. You are absolutely spot on in that the diaphragm itself cannot create the necessary IAP to stabilize the spine. The pelvic floor and the entire abdominal wall are also all crucial part of proper core-stabilization. If any member of the “team” fails the stabilization is compromised. The diaphragm is relatively easy to activate and take control of and it is the “turn key” component of core-stabilization.

      Ref :
      Hodges PW, Butler JE, McKenzie D, Gandevia SC. 1997 Contraction of the human diaphragm during postural adjustments , Journal of Physiology 505: 539-548

  9. David
    David says:

    Great article! Quick question though. I’ve always wondered when we are looking at the abdomen and asking people to take that belly breath down into the lower abdomen what is occuring as the lungs do not extend that far?

    • Hans Lindgren
      Hans Lindgren says:

      Hi David,
      That is absolutely correct that the lungs do not leave the thoracic cavity.
      A properly executed diaphragm contraction makes the diaphragm push down into the abdominal cavity and physically push the organs down, which actually is responsible for the expansion of the abdominal cavity.
      Regards Hans

  10. Christopher Johnson
    Christopher Johnson says:

    Great article Hans! Finally someone has hit the nail on the head. The bottom line is that too many people compartmentalize “core” training. I always tell the athletes and patients that I work with that there is no need to do core specific work because we should always being doing core work…even when we are picking our nose! What I also think is an important piece is the concept of working tension which Kelly Starrett has discussed so we are generating the appropriate amount of tension with this task at hand. Thanks again for taking the time to write this piece.

Trackbacks & Pingbacks

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