Breathing is one of the body's most basic physiological processes, but it's not as automatic as we think. It's something we do without much thought, yet breathing properly is an active process that requires certain muscles to contract.
With proper breathing techniques, such as deep belly breaths, we can lower our stress levels, prevent disease and improve our workouts.
Often, in Western society, people suck their stomachs in while they stick their chests out. This results in poor posture, causing people to breathe shallowly, quickly and/or with the chest only. Shallow or quick breathing provokes the body's 'fight or flight' response to stress by releasing the hormone cortisol. This, in turn, raises your blood sugar and suppresses your immune system, putting you at risk of other health problems such as diabetes and heart disease. By taking a few deep belly breaths, your involuntary response to stress - breathlessness, a pounding heart and sweating - stops.
There are two sets of respiratory muscles, primary and secondary. The primary muscles include those between each rib (external intercostals) and the diaphragm, a thin, dome-shaped sheet of muscle running into the lower ribs and located between the thoracic (upper) and abdominal cavities. If you don't use the diaphragm to its full potential, then the workload moves to your secondary muscles located in your throat, jaw, shoulders and chest. However, these aren't designed for the workload that the diaphragm is (which contracts about 22,000 times a day). Excess use of these secondary muscles can result in aches and pains including headaches.
When the external intercostal muscles contract, the ribs and sternum lift, the thoracic cavity expands forward and backwards, the air pressure in the lungs lowers and air enters. In addition, when the diaphragm contracts, it moves downward, increases the thoracic cavity vertically, lowers the air pressure in the lungs and air moves into the lungs. To exhale, the diaphragm and intercostals relax, allowing the ribs, sternum and diaphragm to return to rest. This then causes an increase in air pressure in the lungs and air is exhaled during quiet breathing, where the predominant muscle is the diaphragm.
However, when we exercise, other muscles become important. The most important are those of the abdominal wall, for example, the rectus abdominus, internal and external obliques and transverse abdominus. They drive the intra-abdominal pressure up when they contract, pushing up the diaphragm, raising air pressure which pushes the air out.
