|This article may rely excessively on sources too closely associated with the subject, preventing the article from being verifiable and neutral. (July 2011)|
Diaphragmatic breathing, abdominal breathing, belly breathing or deep breathing is breathing that is done by contracting the diaphragm, a muscle located horizontally between the chest cavity and stomach cavity. Air enters the lungs and the belly expands during this type of breathing.
This deep breathing is marked by expansion of the abdomen rather than the chest when breathing. It is considered by some to be a healthier way to breathe, and is considered by some a useful form of complementary and alternative treatment.
According the National Center for Complementary and Alternative Medicine, "12.7 percent of American adults [have] used deep-breathing exercises... for health purposes," which it describes as follows, "Deep breathing involves slow and deep inhalation through the nose, usually to a count of 10, followed by slow and complete exhalation for a similar count. The process may be repeated 5 to 10 times, several times a day."
According to the University of Texas Counseling and Mental Health Center, "Diaphragmatic breathing allows one to take normal breaths while maximizing the amount of oxygen that goes into the bloodstream. It is a way of interrupting the 'Fight or Flight' response and triggering the body's normal relaxation response."  They provide a video demonstration. 
In complementary and alternative medicine
Some practitioners of CAM (complementary and alternative medicine) believe that particular kinds of breathing they identify as diaphragm breathing can be used to bring about health benefits.
Deep breathing exercises are sometimes used as a form of relaxation, that, when practiced regularly, may lead to the relief or prevention of symptoms commonly associated with stress, which may include high blood pressure, headaches, stomach conditions, depression, anxiety, and others.
How it happens
The term 'diaphragmatic' is sometimes misinterpreted to imply that the thoracic diaphragm is not used in shallow breathing. This is a misunderstanding, as the diaphragm is actually used in both cases.
Due to the lung expansion being lower (inferior) on the body as opposed to higher up (superior), it is referred to as 'deep' and the higher lung expansion of rib cage breathing is referred to as 'shallow'. The actual volume of air taken into the lungs with either means varies.
Relation to Yoga and meditation
Hatha Yoga, tai chi and meditation traditions draw a clear distinction between diaphragmatic breathing and abdominal breathing or belly breathing. The more specific technique of diaphragmatic breathing is said to be more beneficial.
Relation to Singing
- Shallow breathing - a type of breathing that is mutually exclusive to diaphragmatic breathing and is associated with multiple anxiety disorders
- Circular breathing
- Pranayama - a traditional Yogic practice of slowing and extending the breaths, used during meditation
- Kussmaul breathing
- "Relaxation Techniques for Health: An Introduction" http://nccam.nih.gov/health/stress/relaxation.htm
- http://nccam.nih.gov/health/providers/camterms.htm "Terms Related to Complementary and Alternative Medicine"
- "To relax using this method, you consciously slow your breathing and focus on taking regular and deep breaths...Because relaxation is the opposite of stress, the theory is that voluntarily creating the relaxation response through regular use of relaxation techniques could counteract the negative effects of stress...Chronic stress may lead to high blood pressure, headaches, stomach ache, and other symptoms. Stress may and in many cases will worsen certain conditions, such as asthma. Stress also has been linked to depression, anxiety, and other mental illnesses." - Relaxation Techniques for Health: An Introduction