The principal muscle involved in abdominal breathing is the diaphragm, a strong dome-shaped sheet of muscle that separates the chest cavity from the abdomen.
When we breathe in, the diaphragm contracts and pushes downwards, causing the abdominal muscles to relax and rise. In this position, the lungs expand, creating a partial vacuum, which allow air to be drawn in. When we breathe out the diaphragm relaxes the abdominal muscle contract and expels air containing carbon dioxide. Of the two major types of breathing, diaphragmatic breathing is the most efficient because greater expansion and ventilation occurs in the lower part of the lung where the blood perfusion is greatest.
In children and infants the diaphragm is the sole muscle for respiration, so if you watch an infant breathing you should get a good idea of what diaphragmatic breathing is like.
As the diaphragm contracts it pushes the abdominal organs downwards and forwards, and this rhythmical massage gently compresses the organs and improves circulation.
Diaphragmatic breathing in conjunction with physical and mental relaxation has been found to reduce high blood pressure and anxiety significantly. When we are calm and composed our breathing is diaphragmatic, and since there is a reciprocal relationship between breathing and the mind, practicing diaphragmatic breathing leads to mental relaxation.
It is the most important tool available for stress management. It promotes a natural, even movement of breath which both strengthens the nervous system and relaxes the body. It is the most efficient method of breathing, using minimum effort for maximum oxygen. The following are the main benefits,
(1) Providing the body with sufficient oxygen.
(2) Expelling carbon dioxide adequately.
(3) Relaxing the body and the mind.
(4) Improving circulation to the abdominal organs.