There are two ways to breathe: (1) chest breathing (ribs expand and contract) and (2) abdominal breathing (abdomen expands and contracts).
Chest breathing is often referred to as shallow breathing as it only uses the top third, half of the lungs which often increases the rate of respiration, need for more breaths to make up for lack of efficiency. Deeper breaths take in more oxygen, let out more carbon dioxide and are much more satisfying, energizing requiring less breath, just like sleeping. The body mind requires a certain amount of oxygen. Anything less overworks the lungs produces more breaths.
Deep abdominal breathing uses the expansion and contraction of the abdomen to draw the breath deep into the lungs filling it from the bottom to the top, and then emptying it the same way, order. The breath is inhaled through the nose and into the stomach, abdomen, which naturally expands, and exhaled, squeezed out via the contraction of the abdomen. A full exhalation complete with a “ha” sound tends to empty the lungs of any stale air and is often practiced first thing in the morning as the air in the lungs tends to stagnate, get stale, stagnant during the night, when the body is less active. The breath can also be held, which increases the absorption of oxygen. Do not hold the breath when the air is impure.
Deep abdominal breathing is highly efficient and less stressful on the lungs as the amount of breaths per minute are decreased. There is a belief in Taoism that we are given a certain amount of breaths, just as if we are given a certain amount of jing. When those breaths run out, death ensues. Therefore, you can theoretically extend life by reducing the frequency of the breath. Most people breathe (inhale and exhale) approximately ten times per minute. Life could be extended if the rate were slowed down to five to seven breaths per minute. The breath like any function uses chi, blood and jing; the more you breathe the more chi, jing and blood you use, the faster you age. The less you breathe, the less chi, blood and jing are used, the less, slower you age.
Deep abdominal breathing can also be done in reverse. The abdomen contracts with the inhalation and expands with the exhalation. This is the same way that a baby, fetus breathe inside the womb, via the umbilicus which is why it is sometimes referred to as embryonic breathing. The lungs are still filled and emptied from bottom to top.
Deep abdominal breathing can be done standing, sitting or lying down. You can train yourself to breathe abdominally by placing your hands on your abdomen. As the breath is inhaled, the abdomen, hands are pushed out. The exhalation is the reverse. The hands, abdomen pushes in. Deep abdominal breathing takes training. Women that are pregnant or menstruating should not do deep abdominal breathing as it may create downward pressure.
Deep abdominal breathing, which moves the diaphragm up and down, massages the internal organs, increases digestion, absorption and elimination. The diaphragm is the partition of muscles and tendons that separate the chest cavity from the abdominal cavity.
Deep abdominal breathing can also tone the kidneys, jing. In Taoism it is said that the breath can be taken down into the lower abdomen, lower tan tien (below the navel in the middle of the body) where it can unite with jing. This requires visualization, imagination. The mind directs the chi. Chi is breath.