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This idea came to me motivated by the dreadfull popping sound of my vertebrae during my first and only manipulation.
The chiropractor popped his fingers before the procedure right in front of me, "preparing me" for what was to come; the sound of maybe ten of my vertabrae popping like popcorn in the oven while he pressed once, shortly and decisively with both palms of his hands crossed on my spine! He explained me that the sound i will hear during the adjustment comes from the CO2 instantly boiling in the disk due to low pressure in a similar way the sinovial fluid would if you extended the articulation of you fingers and make them pop, due to the relative vacuum being created in the articulation (sinovial fluid). Obviously, he lost too many clients after the first visit that made it worthy to pop his fingers. As i was skeptic, he did it with several fingers until i started feeling for him.
I was never able to pop my fingers :( , but ever since i tried to figure how you can create vacuum in the disk by simply pressing perpendicularly on the axis of one's spine.
What's happening is the disks are being deformed as following: one side of the disk is being compressed and the other extended due to the fact that the angle between the axis of two adjacent vertebrae is changing. This can be observed in the pictures.The deformation is not equal on both sides. The compression on the side close to where the force is being applied during manipulation is smaller than the extension on the other side because the disk has a gel like structure inside but a hard "skin". During this procedure the disk is less compressed on one side than extended on the other. The result is a relative vacuum being created in the gel area that allows the eventual bulge to be sucked back in. It is literally a reduction or at least a partial reduction of the disk hernia.
The same with the succession of cat and dog yoga poses. The effect of this succession is very similar to the "adjustment" the chiropractors do.
This vacuum inside the disk is similar to what they obtain using traction machines, except is local and stronger. The traction machines extend all the spine and a few other articulations and then the extension effect is somewhat attenuated by a number of disks and articulations being extended in the same time.
Usually the explanation chiropractors themselves give about how it works is differrent, like alignement, subluxations and things like that. But if my explanation is the true one, it could lead to improvement of actual practices since it is obvious that the patient would benefit of rest after manipulation. If there is reduction of bulge that occurs the effect of reduction will be partially reversed by the compression created during standing and walking. With rest, the healing will be much faster and the number of manipulation decreased.
Although we cannot be sure of this either. Another phenomenon that occurs during manipulation is a hydraulic shock in all the adjacent tissues. The popping sound is there to prove it. This create a slight inflammation in all the surrounding tissues thus increasing the blood flow and accelerating the healing of the disk which is the biggest organ in the body that does not have its own blood supply and sucks its nutrients from the surrounding tissues. By walking and maintaining a higher heart rhythm and blood pressure, this effect is improved.
