In many ancient exercise such as qi gong, yoga, tai chi, as well as traditional and modern meditational exercise includes learning the importance of breath.
Dr Gabriel Cousins has said “at least ninety percent of our metabolic energy should come from our breathing”. Also Chinese medicine say Qi (energy) can be obtained from our food as well as the air we breathe.
The air is needed to oxygenate the cells keeping them health and functioning optimally. Unfortunately we have forgotten how to breathe in a full capacity. Breathing correctly can help build and strengthen the chest and lung muscles. improved lung capacity leads to a greater strength, endurance and overall health as it will help cells, digestive, brain, immunity system to function well. When the energy is up in our head most of the time (thinking, worrying and stressing) it is important to bring the energy back into the body to ground yourself.
There seems to me a few variation of “the best way” to breathe. You may like to do your own research and see what works for you.
A breathing technique that I have been experimenting lately is breathing exercise for grounding and longevity, also called taoist breathing. That is to stimulate all parts of the body – lower, middle and upper belly, sides, lower back and kidney, upper back, and brain. This exercise can internally massage inner organs, as well as improving circulation, performance and reduce stress. It also helps you cope with negative emotions, such as fear and anger. It needs to be done slowly, in a harmonious balancing way.