This morning it occurs to me that I wasn’t very clear, about reverse breathing.
I believe it’s based on this:
In a bent-knee posture, the spine is supported by the horizontal ilio-lumbar ligaments in exhalation, and by the vertical ilio-lumbar ligaments in inhalation. When support is realized relative to the direction of breath, the abdomen moves slightly outward on exhalation, and slightly inward on inhalation, yet only relaxation of activity and feeling of the whole body with no part left out is involved.
Lately I focus a lot on turning to the left, turning to the right, following up behind–stretch in the ilio-tibial bands and action in the sartorius, gluteous, and tensor muscles carries into the abdominals to sustain pressure in the fluid ball of the abdomen, and stretch in the lumbodorsal fascia behind the sacrum. Here’s a practice Gautama the Shakyan described for the cultivation of psychic powers:
So (one) abides fully conscious of what is behind and what is in front.
As (one is conscious of what is) in front, so behind; as behind, so in front;
As below, so above; as above, so below;
As by day, so by night: as by night, so by day.
Thus with wits alert, with wits unhampered, (one) cultivates (one’s) mind to brilliancy.
(Samyutta-Nikaya, Volume V, 263; Pali Text Society translation volume V, pg 235)
No further explanation was offered for “before as behind, behind as before”, yet I would say it’s exactly “turning to the left, turning to the right, following up behind” (which is Yuanwu’s description, from “The Blue Cliff Record” case 17). With regard to “above as below, below as above”, Gautama described mindfulness of each part of the body and of the internal organs, from the soles of the feet to the crown of the head and from the crown of the head to the soles of the feet, just as is (I tend toward “soles to crown” on inhalation, and “crown to soles” on exhalation–in the dentist’s chair, I found myself holding my teeth with my feet, and my feet with my teeth, not exactly “as is”). “As by day, so by night: as by night, so by day” referred to observing the sign of the concentration.
There’s a happiness in the relinquishment of volition in inhalation and exhalation.