Most of us, however, do not breathe deeply under normal circumstances, so it may help to review the mechanics of deep breathing and how it helps us to relax. When prehistoric humans were in danger of attack, their muscles tensed and their breathing became rapid and shallow, as they prepared to run or fight. Their high level of tension was a means of preparing their bodies for optimum performance. However, since we're not running or fighting, our tension has no release and our stress response builds. How Deep Breathing Works Deep breathing is not always natural to adults.
Most adults breathe from the chest.
This is shallower breathing, so less oxygen is taken in with each breath. As a result the blood is forced to move through the system quickly so that enough oxygen gets to the brain and organs. Higher blood pressure results. Deep breathing can reverse these effects. Take some time to practice this kind of breathing each day, especially when you're under stress.