Diaphragmatic breathing

Diaphragmatic breathing, or deep breathing is the act of breathing deep into your lungs by flexing your diaphragm rather than breathing shallowly by flexing your rib cage.

This deep breathing is marked by expansion of the stomach (abdomen) rather than the chest when breathing. It is generally considered a healthier and fuller way to ingest oxygen, and is often used as a therapy for hyperventilation and anxiety disorders.

Overview
Performing diaphragmatic breathing can be therapeutic, and with enough practice, can become your standard way of breathing.

To breathe diaphragmatically, or with the diaphragm, one must draw air into the lungs in a way which will expand the stomach and not the chest. It is best to perform these breaths as long, slow intakes of air - allowing the body to absorb all of the inhaled oxygen while simultaneously relaxing the breather. To do this comfortably, it is often best to loosen tight-fitting pants/belts/skirts as these can interfere with the body's ability to intake air.

While at first one may not feel comfortable not expanding the chest during breathing, diaphragmatic breathing actually fills up the majority of the lungs with oxygen, much more than chest-breathing or shallow breathing.

Exercises
A common diaphragmatic breathing exercise is as follows:

1. Sit or lie comfortably, with loose garments

2. Put one hand on your chest and one on your stomach

3. Slowly inhale through your nose or through pursed lips (to slow down the intake of breath)

4. As you inhale, feel your stomach expand with your hand. If your chest expands, focus on breathing with your diaphragm

5. Slowly exhale through pursed lips to regulate the release of air

6. Rest and repeat

Caveat
One thing to note is that for some, the diaphragm is dysfunctional or entirely non-functional, in which case one should focus on slow inhalation and exhalation (through the nose and pursed lips).