Several of my PT friends have referenced a physical therapist p who has studied breathing named Mary Massery. In her articles, she has referenced the idea of "intra-abdominal pressure"


See page 2

If I am understanding her correctly, she is basically saying that

  • an unopened soda can is sealed and hard because of the pressure inside the canister
  • the human trunk tries to support itself upright. In this sense it is rigid. Therefore, it too must be using an internal pressure to create the rigidify necessary for uprightness. This is what she calls "intra-abdominal pressure."

My Question

Given what is known about the mechanics of human breathing, do the pressures of the abdominal cavity actually behave this way? Does the abdominal cavity rigidity itself using some sort of pressure? If so, how does this pressure mechanism relate to the mechanisms used during respiration?

If I am understanding her model correctly, I am extremely skeptical. A soda can is really not similar at all physically to the abdominal cavity.

  • $\begingroup$ Given our chat, I am confused whether this question is on posture (ref. question title) or on respiration (ref. body question). What exactly is your question? $\endgroup$
    – AliceD
    Sep 29 '15 at 2:59
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    $\begingroup$ I was previously trying to understand respiration in an attempt to understand how pressure is utilized in the body during breathing. My logic was if I can better understand how pressure is utilized during inhale, I would have enough info to answer this postural question myself. Nathan's answer wasn't sufficient. It didn't actually address the levels of pressure in the abdominal cavity itself and how that works with respiration. My ultimate goal was understanding this issue. But I got the sense the respiration approach seemed to not be specific enough, so I am presenting a different viewpoint $\endgroup$ Sep 29 '15 at 3:28
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    $\begingroup$ @AliceD Massery's claim is that posture is dependent on respiration in a sense. She seems to be making some claim about how pressure in the abdomen affects posture. At least, I think that is what she is saying. $\endgroup$ Sep 29 '15 at 3:30
  • $\begingroup$ Great, thanks for explaining. I took a quick look at the cited abstract and it seems that the author is simply saying that bad posture impairs breathing, but I just took a quick glance. $\endgroup$
    – AliceD
    Sep 29 '15 at 3:40
  • $\begingroup$ Haha I would argue my answer was sufficient to the question, which had no words like "intra-abdominal pressure" or even posture in it. Hope you find what you're looking for, though intuitively a meaningful relationship between the two sounds bogus to me. $\endgroup$
    – Nathan
    Sep 30 '15 at 15:08

I found this review which can help to clarify this notion of intra-abdominal pressure : Intensive Care Med. 2009 Jun;35(6):969-76. What is normal intra-abdominal pressure and how is it affected by positioning, body mass and positive end-expiratory pressure? De Keulenaer BL1, De Waele JJ, Powell B, Malbrain ML. The authors mention that there is indeed a positive pressure in the normal subject. This IAP is contributed by gravity, uniform compression (abdominal contraction, diaphragmatic contraction, mechanical ventilation, rib cage excursions) and shear deformation, this last one depending on the intrinsic stabilty of the tissue. The authors conclude that "the abdomen behaves as a hydraulic system with normal IAP of about 5–7 mmHg..". Kind of a can of soda, without the bubbles... Pathologies affecting this pressure are named "abdominal compartment syndrome) and result from multiple etiologies (obesity, trauma...,).

  • $\begingroup$ This addresses the IAP issue, but not the actual question about posture. $\endgroup$
    – kmm
    Sep 30 '15 at 12:20
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    $\begingroup$ @kmm. Right, but I would say that this amount of pressure is not enough by itself to maintain a rigid posture. As a comparison a tyre normally filled at 2 bars is at 1500 mm Hg. $\endgroup$
    – user18963
    Sep 30 '15 at 14:13

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