There has been a lot of research showing that slow and deep diaphragmatic breathing has valuable effects on the brain and body. The diaphragm is located between the chest and abdominal cavity. It is the major muscle of breathing. This dome-shaped muscle contracts and flattens when one breathes in which gives more height in the thoracic cavity, allowing more air to come in with increased lung volume. With expiration the diaphragm relaxes. Interestingly, the diaphragm has a massaging effect on the organs beneath it (including the digestive organs) when one takes a deep breath.
This practice involves taking slow, deep breaths using the diaphragm muscle and minimum movement of the chest. One recommendation is to sit up straight (or lay flat), take slow deep breaths in through the nose, and with one hand on your abdomen feel the abdomen move in and out rather than focusing on the chest.
The journal Medicines says that diaphragmatic breathing has a modulating effect on the nervous system and impacts the respiratory, brain, cardiovascular, and gastrointestinal systems. As well, the authors from Physiopedia report the benefits of diaphragmatic breathing consist of:
There are several videos, apps, and wearable devices on the market one can use to help track their diaphragmatic breathing.