The forms we use to train the body in Zen – how to sit, stand, and so on – can be described in general like this: the energetic currents of the body are gathered with the breath at the tanden and in the lower portion of the body, the sacrum drops, the spine extends upward, and the eyes are used broadly and with sharpness. There are several effects of this, but we can essentially say that a downward settling or grounding is combined with an upward lift or extension. The body thus integrated, these two forces balance or cancel one another. In this condition the mind easily enters samadhi and kiai – vital energy – radiates. We should understand that such energy is not produced somehow from practice, but rather flows through the body-mind when it is balanced in these ways.
(Meido Moore, “American Zen” group, Facebook Jan. 31st 2019 post)
It’s my belief that the better the description of what’s really happening in the posture/carriage, the more we can all drop into the experience.
In particular, this:
There are several effects of this, but we can essentially say that a downward settling or grounding is combined with an upward lift or extension.
Here’s something I wrote to a friend, along the same lines:
Experiencing the center of gravity as a point can kick off activity in the pelvis and legs, activity that returns to the abdominals to create a slight pressure (in the abdominal cavity). That slight pressure can shift the lumbodorsal fascia behind the lower spine to the rear, providing support to the structure of the spine and allowing the further alignment of vertebrae.
As far as the application in sitting, the force-counterforce at the center of gravity is the heart of the matter. I focus on the center of gravity and hold the activity around that. In doing so, I keep the strain out of my pelvis and my legs, and land the stretch where it belongs–creating support for the spine and reinforcing the singularity of the center of gravity.
Meido Moore also mentions a lowering of the sacrum, an extension of the spine, and a particular useage of the eyes.
Moore says “the sacrum drops”. I think what really drops is the place where the extensor muscles press against the fascia behind the sacrum. H. F. Farfan describes the press behind the sacrum as “a peculiarity of the erector (extensor) muscles of the spine”:
Below the level of the fifth lumbar vertebra, the muscle contracts in a compartment enclosed by bone anteriorly, laterally, and medially. Posteriorly, the compartment is closed by the lumbodorsal fascia. When contracted, the diameter of the muscle mass tends to increase. This change in shape of the muscle may exert a wedging effect between the sacrum and the lumbodorsal fascia, thereby increasing the tension in the fascia. This may be one of the few instances where a muscle can exert force by pushing.
(“Mechanical Disorders of the Low Back”, H. F. Farfan, pg 183)
My assumption is that the center of gravity generates activity in the pelvic floor muscles, activity that pivots the tailbone and sacrum slightly toward the pubic bones, and lowers the press of the mass of the extensors on the lumbodorsal fascia.
The stretch of the lumbodorsal fascia by the extensors is carried upward, as pressure from the “fluid ball” of the abdomen displaces fascia behind the lower spine. This accounts for the extension of the spine in Moore’s description.
I would say that the use of the eyes “broadly and with sharpness” that Moore mentions follows from the distinction of the natural place of occurrence of awareness from a particular place of occurrence associated with contact in the visual field. I often feel that my awareness is located directly behind my eyes, and yet if I allow my other senses to enter into the placement of awareness, the location of awareness can shift and move.
The location of awareness that shifts and moves leads the center of gravity, and through change in the center of gravity, generates posture and carriage in the body. Because the location of awareness is affected by activity in the senses, and even by activity outside the conscious range of the senses, the action that is effected by the center of gravity is as Meido Moore said:
We should understand that such energy is not produced somehow from practice, but rather flows through the body-mind when it is balanced in these ways.