My first teacher said that we should have a long, deep, complete exhalation, pushing our belly out as we press down, and a short natural inhalation. I am sorry to say that I believe these instructions to be completely mistaken.
Dogen said hardly anything about the breath. He just said to let a short breath be short and a long breath be long. At first glance, these instructions aren’t exactly comprehensive, but I think the import is clear: we shouldn’t try to control our breath.
Sometimes this is rendered as an instruction to just breathe naturally. Note the word. Not breathe normally, as you would when slumped over your computer, or slouching in a chair, but naturally.
Naturally for the zazen posture. When we are balanced, it is as if there is a vast cavern of breath inside us. There is nowhere it doesn’t reach. Sometimes it is breathing the bones of our pelvis. Sometimes our belly. Sometimes our intercostal muscles. Sometimes our clavicle. Sometimes our head. This natural breath breathes us, and as long as it does so, the body is no longer ‘the body’. It is no longer an object in our consciousness. It – everything – is free.