3 Part Breath

I wrote a post the other day about my first yoga class where we were taught "3-part-breath", or "yogic breathing", and that I learned in that first class that my own breath pattern - my habitual and unconscious breath pattern - was actually the opposite of this and called "reverse breathing".  
I think of 3-part-breath as our natural breathing pattern. It's natural to us, but often lost as we navigate life and the inevitable stresses, conditioning and trauma of being in a body in this world.  
If you watch babies, and most young children and animals when they're relaxed, you'll notice that they're whole body moves in sync with the breath, in a coordinated way.  The inhalation expands the lower belly, that expansion rises up into the rib cage, the ribs gently flair out & then the chest and collarbones expand.  On the exhalation, the belly draws in toward the spine, and the cycle continues.  It is a wave-like motion; the breath flows in & expands the abdomen, ribcage & chest, subtly arching the spine, then flows out, and the subtly flexes.   
With stress and trauma, or social conditioning, we might develop a habit of unconsciously bracing the abdomen, or holding the belly.  This compromises the natural flow of our breath, and over time can cause a number of health issues.  
"Reverse breathing" means that instead of the belly expanding when we breath in, the chest expands, and the abdomen draws in.  
The good news is, that with time & patience, we can re-train the body to breath better.  It is worth the effort, as every system of the body, and our life-force and energy levels are impacted by our way of breathing.
A consistent yoga class with a teacher who understands the importance of breath, or a well rounded breathwork practice, starting with a breath assessment with a yoga therapist or qualified breathing specialist is a good way to start the process of re-establishing a natural and beneficial breathing pattern.