[jfengel]

I still don't really get it. All breathing is caused by the contraction of the diaphragm, with some help from the intercostals.

There seems to be something going on with the shoulders: "chest breathing" raises them, but I don't know why, or what effect that has.

In the end, why does it matter? The goal is to get oxygen to the alveoli, and that happens either way. Most people are walking around with fully O2-saturated blood. If anything, the book "Breath" suggests that's the problem: we're all breathing too deeply, and we should be learning to tolerate lower O2 sat and higher carbonic acid levels.

I mentioned the theory to a pulmonary doctor, who hadn't read the book but clearly thought it was bullshit, at least from my thirdhand description.

I try the 4-7-8 thing on occasion, and don't notice anything much beyond the basic calming of focusing on the breath. I feel like there are gaps in my knowledge here, and there may be something to it but it doesn't make physiological sense to me (and the "mystic" interpretations of it are entirely unedifying).