There are four stages of breath control. In practice, these four stages are strung together in a smooth continuous sequence, like the rise and fall of waves on the sea, with each one playing a particular role, and all of them orchestrated by the diaphragm.

Inhalation
Compression
Exhalation
Intermission

Inhalation:

With empty lungs and nostrils flared, relax the diaphragm and commence a soft, slow, smooth inhalation through the nose, deliberately drawing the air deep down into the bottom of the lungs so that the diaphragm descends, and the abdominal wall expands. As the lower lobes of the lungs fill up with air and the abdomen swells, continue breathing in slowly and deeply, so that the mid-sections of the lungs begin to fill next, causing the ribcage to expand. When the lungs feel comfortably full, and both the abdomen and ribs have expanded, draw the inhalation to a halt. Do not try to "top off" the upper lungs by taking an extra gulp of air, for this will make you hunch up your shoulders and tense your neck and also cause the diaphragm to rise. A full breath means that the lungs are about two-thirds to three-quarters filled, with most of the air packed down into the lower and middle sections. In shallow chest breathing, only the narrow upper pockets of the lungs get filled, which represents only about a quarter of the lung capacity, but due to years of shallow breathing, people tend to feel that they must fill up these pockets to get a full breath. Practice will eliminate this tendency.

Compression:

This phase is quite brief, usually only three to five seconds, but its benefits are deep and manifold. Longer retentions of breath should only be practiced under the personal supervision of a qualified teacher. The first step in the compression phase is to press the diaphragm firmly downward to settle the air into the bottom of the lungs and compress the abdominal cavity. As you do this, apply the Three Locks, which are described in the next section.

When properly performed, this brief retention of breath provides several important benefits. It slows down and deepens the pulse of the heart, and balances blood pressure throughout the circulatory system. By increasing the pressure of the air against the surface of the lungs and holding it briefly, this compression greatly enhances the exchange of gases, enriching the blood with extra supplies of oxygen and allowing more elimination of carbon dioxide. It also improves gas exchange between the bloodstream and cells throughout the entire circulatory system, increasing the partial pressure of oxygen against the walls of the capillaries.

Even the briefest breath retention triggers cellular respiration, an innate response that causes cells to "breathe" by themselves whenever breath is held in the lungs. When this happens, blood sugar is spontaneously broken down by the cells to release oxygen and produce body heat. This is the basis of the so-called "dive response" that allows seals to dive deep into ice-cold water for prolonged periods without breathing, and young children who fall into frozen rivers and lakes to survive underwater for up to two hours and revive without brain damage when rescued. In most adults, this response has atrophied, but a few years of deep breathing practice usually suffices to restore it.

Never hold the compression phase of breath beyond what feels comfortable. If you feel compelled to gasp or burst out on exhalation, it means that you've held the compression too long and lost control of your breath. The next time, don't hold your breath as long.

Exhalation:

When you're ready to exhale, release the Three Locks (see next section), relax the diaphragm and ribs, and begin exhaling slowly and evenly in a steady continuous stream through the mouth, which facilitates elimination of stagnant air and energy.

Empty the lungs in reverse order of inhalation, starting from the top of the lungs, then the middle, and finally the bottom. Continue exhaling until the lungs are empty, letting the abdominal wall collapse and contract inward, and the diaphragm ascend upward into the chest, and then expel the last residues of air from the lungs by drawing the abdominal wall farther inward. The entire exhalation should be performed in a long, slow, even stream, not in a sudden explosive burst. If the latter occurs, shorten the compression phase on the next round.

Intermission:

When the lungs are empty and exhalation is complete, do not immediately start drawing in the next inhalation. Instead, pause briefly to let your diaphragm and abdominal wall relax and fall back into place in preparation for the next breath. If you start inhaling while the diaphragm and abdominal wall are still drawn in, the breath will tend to rise up in the lungs, making it more difficult to sink the air down to the bottom. The intermission phase should also be used to check the shoulders and neck are fully relaxed and posture is correct, but do not pause too long, or you'll find yourself sucking in the next inhalation in a short sharp gulp.