D. L. Bartilink took measurements of the pressure generated in the abdomens of weightlifters as they lifted weights. From his measurements, he concluded that the abdominal muscles generate pressure in the “fluid ball” of the abdomen (as he termed it) in proportion to the amount of weight that is lifted. He surmised that pressure generated in the abdomen supports the lower spine, especially when the curve of the lower spine is flattened (as it is when weight is first lifted) (1).
Bartilink theorized that animals (as well as humans) make use of pressure in the “fluid ball”:
Animals undoubtedly make an extensive use of the protection of their spines by the tensed somatic cavity, and probably also use it as a support upon which muscles of posture find a hold… (1)
Through measurements of electrical activity, Bartilink found that the muscles that induce pressure in weight-lifting are the transverse and oblique abdominals, along with the muscles of the pelvic floor; the diaphragm and rectus are not involved. The diaphragm, he stated, can move freely even with pressure in the abdomen from the other muscle groups. This, he speculated, might be an evolutionary step:
Breathing can go on even when the abdomen is used as a support and cannot be relaxed. This means that the range of flight of an animal having the lungs outside the fluid ball is greater than that of an animal who has its lungs in the single body cavity, which can just make a spurt and then has to stop to breathe. Could it be that it is for this reason that the mammals have developed a diaphragm? (1)
The abdomen can be made to provide support without the use of the abdominal muscles if the breath is held and pressure is applied by the diaphragm, but as Bartilink noted, to use the diaphragm in such a manner may defeat the purpose of having one.
Moshe Feldenkrais observed that people often hold their breath when they get up out of a chair. He saw the restriction of the movement of breath as a failure to realize physical equilibrium as the basis for movement; he explained how the movement of standing follows from a state of equilibrium and a shift in the center of gravity:
…good upright posture is that from which a minimum muscular effort will move the body with equal ease in any desired direction. This means that in the upright position there must be no muscular effort deriving from voluntary control, regardless of
whether this effort is known and deliberate or concealed from the consciousness by habit.
…When the center of gravity has really moved forward over the feet a reflex movement will originate in the old nervous system and straighten the legs; this automatic movement will not be felt as an effort at all. (2)
To help his students learn how to stand without holding their breath, Feldenkrais taught three simple exercises that could be done while seated on a chair: first, he said, lean the upper body forward and backward; second, tip the upper body from side to side; and third, with the torso, neck and head held in a straight line, circle the top of the head around the base of the tailbone.
The exercises that Feldenkrais provided engage the vestibular organs through movement of the body. The vestibular organs detect motion in the three spatial planes, and provide the sense of equilibrium. Important to their function are the otoliths, structures inside the vestibular organs that respond to gravity and movement.
To perceive a center of gravity one more sense must be brought into play, and that is proprioception, the sense of the relative positions of the parts of the body (initiated by proprioceptors in the muscles, tendons, and joints).
My experience is that if awareness of the senses comes forward, and in particular if awareness of the vestibular, otolithic, and proprioceptive senses comes forward, then activity to generate or sustain pressure in the “fluid ball” of the abdomen takes place automatically as the long or short of inhalation or exhalation is comprehended.
The practice that Gautama the Buddha described as the “the best of ways” (3) opens with these particulars:
Mindful [one] breathes in. Mindful [one] breathes out.
Whether [one] is breathing in a long (breath), breathing out a long (breath), breathing in a short (breath), breathing out a short (breath), one comprehends “I am breathing in a long (breath), I am breathing out a long (breath), I am breathing in a short (breath), I am breathing out a short (breath).” (4)
In my experience, the relaxed comprehension of the long and short of inhalation and exhalation is only possible when there is support for the spine from pressure in the “fluid ball”
of the abdomen. The pressure in the “fluid ball”, meanwhile, is generated through activity initiated by the “old nervous system”, as a reflex response to the location of my awareness.
I identify my self with the location of my awareness, and for me as for most people, the location of that awareness is singular. There are people who experience themselves as being in two locations at once during a particular kind of out-of-body experience, but this is rare (5). When I sense where I am, I can experience the motions that Feldenkrais pointed out as a part of my sense of where I am, and I can likewise experience the weight and placement of the muscles, ligaments, and joints of the body as a part of where I am.
The trick is to allow for movement in where I am, even when I’m not moving. It’s a trick because my eyes can reset my sense of location in space, and I become accustomed to feeling the location of my awareness as fixed with respect to my eyes. I think I learned to disassociate where I am from what I see by sitting in the dark, and by continuing to practice through the experience of actually falling asleep.
The flattening of the lower back in a seated posture, especially in the half or full lotus posture, can precipitate the experience of the vestibular, otolithic, and proprioceptive senses as awareness takes place, out of a need for support for the lower back in inhalation or exhalation. What Gautama referred to as the comprehension of the long and short in inhalation and exhalation is only natural in such circumstances, to engage the reflex activity of “the old nervous system” appropriately.
Dogen’s Soto school is especially associated with a teaching that the activity of zazen (literally, “seated Zen”) requires no special effort. The science provided by D. L. Bartilink and the description provided by Moshe Feldenkrais make possible an explanation of why that is: the senses come forward naturally out of necessity, and with the experience of the particulars of sense, activity to pressurize the “fluid ball” of the abdomen takes place automatically in support of the spine. The activity of zazen is really “reflex movement (that originates) in the old nervous system”, and no special effort is required.
2) “Awareness Through Movement”, Moshe Feldenkrais, pg 76, 78.
3) Sanyutta Nikaya V, 326-327, Pali Text Society volume 5 pg 289.
4) MN III 82-83, Pali Text Society III pg 124.
5) Blanke and Mohr, “Out-of-body experience, heautoscopy, and autoscopic hallucination of neurological origin Implications for neurocognitive mechanisms of corporeal awareness and self consciousness”, Brain Research Reviews, Volume 50, Issue 1, 1 December 2005, Pages 184-199.☞ A Natural Mindfulness–PDF