Yes yes breathing is key and breathing is meant to be swift powerful inhales through the nose and controlled, long exhales through the nose.    And all of it is timed to the rhythm of movement, so when alternating between poses breathing correctly is focus.  Engaging body and muscles at end of inhale is a focus of mine since my shitlord instructor taught us to focus on tightening lower abs to complete the full exhale. "Imagine your fitter, evil twin is about to punch you in the belly and squeeze those abs."  Yeah.  I promise after hearing this line part of the room burst out laughing and part of us had an image burned into our minds that we never will forget.  The thought of that was enough to scare the shit out of me.  But you know what.  I have abs now.  Fatties respond to the motivation differently.  They give up or they don't come back.    Also yoga is intended to be practiced in warm and even hot environments (which is why I so love hot power yoga!)  And if you aren't doing the poses correctly its a waste of time.  If you are supposed to be in chair pose and you are standing or worse sitting down it does not matter how you breathe. I'm satisfied that the right kind of hot power yoga class is the ultimate shitlord/shitlady experience and there's room for growth at any point.  But the fats don't know that and they will never progress beyond basic introductory stuff.  And most of them quit any way after ten minutes, especially if the teacher is hard core.  I have earned the right to wear my tank top through chaturanga pushups and low plank holds and I obviously take a lot of pride and joy in yoga class and if the teacher was not a shitlord who motivated me to get stronger and better I'd do something else.