Some engaging conversation with an accomplished chiro trying to integrate some of the DNS messages regarding ISSS……..
……(regarding) A-P dimensions, curves, and the thorax I would like to say the following. The depression and change of orientation of the anterior ribs via EO, RA and associated fascia through contraction or manual depression as (I see is possible) adds compression to an already compressed system. This is why in my own body I had come to the conclusion that changing an A-P dimension is not feasible since previous attempts have led to additional and symptomatic tightness. I could drop my ribs in the front, change the curve and angle of the ribs and thoracic curve, but at what expense? If I do this and add compression to the system… well I don’t think this is a good option since I already have a diminished thoraco-costal excursion on breathing and a less than optimal A-P dimension to begin with. ………. Thoughts?
In terms of “changing the thorax,” I think you can consider 2 things.
1) You can change bony contour. It may take forever or some combination of high/low loads and duration, but even in adults it can be done. Look no further than folks that have poorly fitting spectacles digging into their cranium. Bone can change in adults.
2) In certain cases, I don’t think there even is a local change in bone. There is rather a positional change of the bone based on where resting segments are being held. Punctum Fixums and Punctum Mobiles can change as a result of training effects, and bone that appears to look a certain way looks different because they lie in a much different place @ rest or action.
Now that’s not to say no one has a bony deformity, but in the common rib flared postures, I think there are a lot of reasons and techniques to follow to believe the thorax can “flatten.”
You are probably correct that there will be increased spinal compression in a system dominated by stability by RA and EO, the outer core components. That environment can be compensated with flexion, shear, or compression in a number of locations.
If the breath is appropriate over time, the stabilization pattern will shift to multifidus, diaphragm, TA, and pelvic floor. This will leave the outer core a little more “quiet,” and unaffecting to the spinal segments. There will not be more compression; I would expect less if anything. I would expect buttressing to occur through IAP, not bony approximation.
Now “pulling” the ribs down with a crunching type maneuver pulls the ribs into what appears to be a “better” position during the flexion, but the pelvis and t-spine and likely neck are decentrated and inappropriate. In an effort to fight against this tone and track forwards in locomotion, the human body will shift anteriorly in the pelvis, t-spine, and/or neck. All is lost. The breath can depress the ribs and still maintain the vertical spine.
By pressurizing the abdomen, the rib flare will adjust over time. How quickly this takes place is certainly dependent, but once the IAP can be completed in basic positions, holding any exercises for a good breath is part of the endless progressions.
Maybe it is best to suggest it is not as much about depressing the ribs but rather what the depressed ribs represent in terms of motor control of the breath.