Something we do not generally give much attention to (nor should we have to) is our breathing. Yet years of slumping or tension create restrictions in this most vital of functions. Your breathing reflects your habitual posture. Breathing regimes which don’t take this into account do not address how we breathe when we are not thinking about it (which is most of the time!).
It is interesting to reflect that the Alexander Technique began with one man’s breathing problem. Initially he described his work as “respiratory re-education”.
When we slump or hold ourselves with excess tension or both (it is possible!), the ribs cannot move naturally or in coordination with the diaphragm. In allowing the back’s natural length without effort, we simultaneously provide the conditions in which the ribs and diaphragm can move easily and be responsive to the demands we place eg being vigorous vs sedentary. Ideally we work towards the conditions of natural springy length as our way of being. A simple way of supporting this and helping to free the breath is to practice “active rest”, otherwise known as semi-supine.
Lie on your back on a firm surface (eg a carpeted floor) with your head supported so that it is not falling backwards and with your knees raised. This already places a very gentle stretch on your back. Just lie there, with the intent to be as quiet muscularly as possible. Gradually, you may reduce muscular excess while allowing your back to lengthen and to fan out. Don’t be in a hurry, but do be consistent! (I.e. daily) As you allow length and breadth, everything involved in moving air in and out can operate with progressively less interference.