The zone of apposition refers to a vertical area of the diaphragms that begins at their insertion point on the inside of the lower ribs and extends to the top of the diaphragms. If the zone of apposition is present, the diaphragms will be dome-shaped and proper diaphragmatic breathing will occur without recruiting accessory muscles of respiration.
The zone of apposition is dependent on the position of the ribcage.
Ribs can either rotate externally, which is up, or they can internally rotate which is down.
An elevated ribcage has ribs that are in a state of external rotation. External rotation of a ribcage occurs when the lumbar spine is in a state of extension.
A proper ZOA will only occur when the the ribcage is in a state of neutrality, meaning the ribcage (and lower spine) are not in a state of extension. In other words, a proper ZOA can only occur when we can achieve thoraco-lumbar flexion.
Flexion is achieved through internal rotation of the ribs.
In PRI, thoracic/lumbar flexion and its accompanying internal rotation of the ribs is achieved through elongated exhalations that will recruit the external obliques. The internal obliques will rotate the ribs internally (down, back, and in) and then with the transverse abdominals hold them down during the next inhalation.
This is very important to understand.
If the ribs remain internally oriented during the next inhalation, this will force the ribcage to expand.
This ribcage expansion, instead of ribcage elevation, is what we are trying to achieve so that a proper zone of apposition can be found and maintained during respiration.
If the lower back arches upon inhalation, this means that the ribs are externally rotating, the ribcage is elevating as the lower back is extending, and the ZOA will be lost.
One way of helping people to maintain rib internal rotation during inhalation is by putting your hand under their lower back and instructing them to not leave your hand when they inhale. Usually this is done in the 90/90 position with the individual’s knees and hips bent at 90 degrees and feet on the wall.
If their lower back stays in contact with your hand as they inhale, this means that their ribs are internally rotated they are thus relying on rib expansion to breathe.
Because a proper ZOA depends on both proper pelvic and ribcage position, achieving a ZOA, particularly on the left, is an essential objective of all Postural Restoration programs.
For an example of how the ZOA can effect shoulder pain, you can check out this post.
Thank you for this explanation! You make it very easy to understand!
One question:
?Why do you say that we should achieve ZOA, particularly on the left?
Could you explain that further?
Thank you again!
Alison Marsh
Pilates instructor and educator at YourPregnantCore.com
Hi Alison,
I emphasize the ZOA on the left because it’s the most commonly and easily lost.
The ZOA on the right is technically just as important, but due to the way our body is organized on the inside (larger and stronger right diaphragm with a big liver sitting underneath it) and the fact that humans are biased towards our right side, we lose the ZOA on the left more frequently and more easily than on the right.
The typical Left AIC/Right BC pattern results in a loss of ZOA on the left, while it maintains the ZOA on the right.
The Bi-lateral PEC pattern (better known as PEC) results in ZOA loss on both sides because both sides of the pelvis rotate forward and both sides of the ribcage rise. When both sides of the pelvis rotate forward and both sides of the ribcage rise, you lose the ZOA on both sides and are stuck in a state of lower back extension on both sides.
Since the Left AIC/Right BC pattern (that results in a loss of left ZOA) is more common than the Bi-lateral PEC pattern I emphasize the left ZOA.
Also, you’ll never lose just the right ZOA (unless someone’s internal organs are switched around or they have suffered some devastating injury or neurological event). It will always be just the left ZOA, or the ZOA on both sides.
Additionally, if you lose the ZOA on both sides (bi-lateral PEC), the right ZOA almost always restores first (and easily) as indicated by the testing. This is because underneath the bi-lateral PEC is a Left AIC/right BC pattern on a body whose design inherently makes a right ZOA easier to maintain than a left.
No one starts off as a bi-lateral PEC. They start off as Left AIC/Right BC (left ZOA loss) and then can pattern further into a Bi-lateral PEC (loss of ZOA on both sides). The important thing to remember is that this Left AIC/Right BC pattern is completely normal and enables us to move as humans. It’s only problematic when it gets too extreme.
Hope that helps
Neal
THANK YOU SO MUCH N E A L !!!!! Profound answer….I want to type everything in caps….amazing …………….
That is só amazing Alison….I am an almost 70 yr old voice teacher/singer who has basically learned how to sing by studying Dmitri Hvorostovsky….(I’ve had a dozen teachers, went to Manhattan School in NY, studied with 12 teachers from Met singers to top pedagogues etc etc and most of them confused me. Not complaining, oh yes I am, but anyway, your comment above about favoring the left side is so obvious with Dmitri’s stances and movements….I had not noticed this before and thank you so much for posting….(I have been very happy to actually learn how to sing by teaching myself (basically) by modeling DH)….Renee Fleming gave him the highest compliment calling his the most beautiful male voice she had ever heard…they sang together in Eugene Onegin at the Met)
Hello Neal,
It’s nice to read your article and talk to you agian.Thank you very much for your sound tutorials, which help me understand ZOA more.
A question about the forces pull the ribs down during elongated exhalation, you indicate the external oblique(EO) is recruited, how about internal oblique and transverse abdominis? Some PRI exercises emphasize activation of IO and TA, but I haven’t found any to active and inhibit EO. The only information about EO is “external obliques weakness on opposite side”( )
In my case , my left inferior part of EO is harder and stiff, so perhaps the left EO is not working well wholly, and this dis-functional EO makes it hard to restore my left ZOA.
Hi Peter! Thank goodness you commented, because I made an error. I wrote “external oblique” but I should have written that it’s the internal oblique that pulls the ribs down during exhalation. No matter how many times I proofread my writing, it seems I always miss something.
So during exhalation, the IOs pull the ribs down, back, and in and the role of the TA is to hold that new position during subsequent inhalation so that our ribs are forced to expand out laterally and posteriorly rather than move into extension.
Another way to look at the whole picture is that we need to recruit hamstrings to hold our pelvis in a neutral position (and keep us out of anterior tilt) and we need our internal obliques to hold our ribs neutrally, and out of extension.
We then train our ribcage to move posteriorly during inhalation. If you put your arms on a wall in front of you and push yourself backward, that movement protracts the scapula. However, it is also moving the ribcage backwards at the same time. Often people who struggle to get the left ZOA have not yet gotten that posterior ribcage movement due to back tightness preventing the ribs from moving backwards.
Hope that helps and thanks for the comment.
Neal
Hello Neal ,
I appreciate your reply. Yes, I’ve found my left back is tight and so far I’ve practised the Ihibition of paraspinal errtors with Left Hamstring besides 90/90 hip lift. Hope I’ll get some improvement.
One more question: to check whether or not we’ve got ZOA, we must do Hrusk Lift test, right? Is it possible a person’s Hrusk Lift Test is negative, but his/her left ribs looks still flared? This seems my case.
Kind regards,
Peter
Hi Neal,
My name is Marshall and I am in the south suburbs of Chicago. You are amazing. I am a duplicate of the personal horror, and why you started looking for answers. yuk
It is a pleasure to read and hopefully get some help.
Too much pain, to just attend a class due to my condition, so far,and will not be able to use my hamstrings,and such to hold a neutral position for proper ZOA. I am going to attempt my PRI exercises on tomorrow, just to get an idea.
If I am correct, I think my left pelvis has rotated forward and is held by my ANTERIOR INTERIOR CHAIN.
It just looks like my pelvis is tilted(a lot) to the left. I have major pain (all on the left)in my lower back, down outside left leg, really bad at knee, but no pain below knee.I Can hardly walk(but thought it was my history of a herniated disc(gone worst) again. This started Feb 2019.BUT never had a pelvic tilt before now. I am in Phys Therapy, with decompression over a year, miserable.
Phys Therapy experimenting and even suggested to include IT Band exercises. They are wrong!! I now realize my left pelvis is turned inside and not really sticking out(tilted)as it looks.
I hope I am understanding this correctly. It appears no one is available to treat me in the south suburbs of Chicago, Illinois. Do you have anyone, recently trained but not listed yet, in my area? Thank you
Marshall, there are a number of providers in the Chicago area. Definitely in the Wilmette area. Look for Dan Houglum.
Hello Sir,
I read your article on lateral pelvic tilt and zoa.. got my pelvis aligned using 90 90 hip shift video .. very well explained by you.
As I am right handed…I do much of my work using right hand ….though after reading your article I have started incorporating my left hand (left tva and obliques) into day to day activities.
My question is while working out … should I go for bilateral work or unilateral work??
In 90 90 hip shift there is more focus on left side ( i.e. left hamstrings, left obliques etc.) But while trying to do other exercises… should I go for training weaker side more using unilateral work ( supine single leg extension) or training both sides equally using bilateral exercises (e.g. hip bridge)?? As because of Lateral pelvic tilt my one side is weaker and other side is stronger. For example, right glutes seems stronger and left glutes seems weaker.
So after applying 90 90 hip shift and bringing back pelvis in neutral… should I start working out unilaterally or bilaterally??
Also… while performing any exercise … should I always make sure… that my left zoa is maintained by compressing left abs more?
Thanks.
Note: Literally, I have tried thousands different things to get my pelvis aligned … but nothing worked!! After reading your article on lateral pelvic tilt (which is brilliantly explained)for the first time in six years I was walking without limp. I didn’t know where to write thank you note so I am writing it here….
Thanks for the kind words, Nicky! All those questions you asked are good ones and are questions that all trainers have to start pondering once they discover PRI. I think I will write a blog post about just this subject. Personally, I prefer unilateral work because I have a strong right sided pattern and it’s easier to incorporate PRI techniques (ZOA maintenance) into unilateral work. On the other hand, there is certainly nothing wrong with using bi-lateral work. I suppose it depends on your goals. You could always just mix it up and get a moderate amount of both. Life is variable, we breathe, move, and exert force in all sorts of different postures and positions, sometimes inhaling, sometimes exhaling, sometimes holding our breath. So I train all possible scenarios. But my main personal concern is staying out of extension (but again, that’s because I was an extreme PRI type patient).
Ok great…quite clear answer… as always. Thank you for quick reply…. I understand your answer….I am sure … after reading your answer.. I will be able to achieve my goal for optimal posture soon.
Thanks again… God bless…
Is chronic side sleeping on the left side a possible reason for acclerated loss of left zoa?
Hello, Liam. Could sleeping on your left side contribute? Yes.
Thanks a lot Neal for the blog post, it has helped me understand a bit better the ZOA. I have a related question though. When I sidebend to the left and exhale, I feel the left abdominals contracting. However, when I inhale again I lose the feeling of my left abdominals being contracted. According to your post, that means that the transversus abdominis is not holding the position and I am using my back to inhale. I think this is why when I am in the all fours position and I try to inhale into my right chest, I cannot. Because I lose the ZOA even I am rounding my back. How can I train it? Hold my breathing before inhaling again? and then inhaling slowly so that the abdominal contraction is not lost? Thanks a lot!