The other night, I had a few minutes to spare and went to YouTube to see what they offered. I do email, searches, document saves, news reading , translations and texting with Google products so I am not surprised if one of their products has traces of what is currently of interest to me. YouTube suggested Belisa Vranich. She has several books and several videos but I began with this one:
https://www.youtube.com/watch?v=1sgb2cUqFiY
I didn't know anything about her and I didn't expect to get any new important ideas or tips. But I did. Dr. Gay Hendricks, like Dr. Vranich, is a psychologist and I have read and followed him and his helpful books off and on for years. Both have things to say about their experience with people who benefit from modified breathing. Vranich talks to her TED audience about "horizontal breathing." I hadn't heard the term before and I figured it was just a sort of gimmick. But later that night, I deliberately tried her notion of breathing more sideways to expand instead of vertically inflating my chest from top to bottom.
I was surprised at how easily and fully I got a full inhale. Yes, the breath is often used as a concentration point in meditation. Yes, it is one of the few body functions that can continue without attention and can yet be control and affected by conscious effort as well. I think it is impressive that both Hendricks and Vranich are psychologists, not pulmonary experts or even physiologists. They both counsel people and they both report rapid results with their clients when altered breathing is used. I have read that taking a conscious deep breath is a quick way to get into the moment, to pause in mental efforts and focus one's attention on the present and the current surroundings.
Both Hendricks and Vranich emphasize that breathing can assist with stress reduction.
Whether is generalized stress or anxiety or fear or low self confidence or dangerously inflated self confidence, focusing on breathing can assist in moving the mind to a state of more complete awareness and acceptance of one's situation both internally with feelings and externally with problems and possibilities. Some additional leads can be found here: http://fearfunandfiloz.blogspot.com/2016/02/breathing.html