Although according to the eight limbs of yoga breathe work or pranayama is at the fourth limb, I feel it is the most important. I often respond when people tell me they can’t do yoga with, “You can breathe can’t you?”. Controlling the breathe using various techniques can and is very beneficial to the body as well as the mind.
I have yet to lead a class just in breathe work, which would be kind of cool, but I have designated a good portion of time breathing at the beginning of my yin classes to help cultivate a meditative state.
To quote Gary Krafstow, “Asana without breath is calisthenics”. I find the pranayama to be a powerful, deep part of personal practice and opens the potential to regulate my physiology and nervous system.