Mechanics of Breathing

Originally published on LiveJournal, 7.13.08

Many of our intuitions and language about breathing are dead wrong.

It’s quite a challenge to get air into our lungs, less a challenge to get it out. The problem is that Earth’s atmospheric pressure is not even close to high enough to push itself into our body, so we need some forceful way to expand the volume of the lungs in order to pull the air in.

It’s not a mechanically straightforward task. Muscles work by contracting, not lengthening. How, then, can we use contracting force to create expansion? The trick is the relationship between the chest cavity, which can change its volume because of the structure of the lungs, and the abdomen, which can’t change its volume, but can change its shape. Because the two are connected, by bulging the abdomen in various directions we can effect a change of volume in the chest. The key muscle is the diaphragm, which originates in bone and soft tissue in our lower chest, and inserts itself into a central tendon that travels vertically down the spine: “nipple to navel.” As the diaphragm vertically contracts, it can change the relationship between the chest and abdominal cavities. That’s breathing.

Many other muscles help the diaphragm do its work, depending on how we are breathing. During inhalation, we can steady the chest using some muscles, relax the abdomen, and then contract the diaphragm. In this case, it would pull on the central tendon, moving it in and up. Since the abdomen can’t change its volume, this sucking-in of the belly causes it to bulge on its top, towards the chest cavity. Our ribcage is designed to expand as it moves up, so that the force effectively expands the volume. That’s a “chest” breath. At the other extreme, we can steady the diaphragm’s central tendon with some muscles deep in the abdomen, relax the chest, and then contract the diaphragm. This would pull the diaphragm down into the abdominal cavity, creating more space (volume) in the chest, and meanwhile bulging the abdomen outwards. That’s a “belly” breath.

There’s a certain myth that calls belly breathing “diaphragmatic breathing,” as opposed to chest breathing which supposedly is not. The fact is that both types of breathing rely on the diaphragm. It’s true that belly breathing creates more volume for less energy than chest breathing, but it’s wrong to flat-out recommend it. We use our body in so many ways, angles and configurations, such that often belly breathing is simply impossible. Locations of the hips and legs, the position and rotation of the spine, can effect their own changes on the shape of the abdomen, such that the pure effect of the diaphragm’s movement, described above, would not create effective breathing. In such cases, chest breathing is a very successful alternative.

In fact, there are variations in between. Depending on the position of the spine, the contractions of the diaphragm can also be anchored closer to its center, causing the chest and central tendon to move towards each other. How it effects the relationship of the abdomen and the chest again depends on many factors.

The bottom line is that you should practice breathing in a diversity of configurations, with all kinds of the pressures on the body, in order to be an effective breather. There’s no generally wrong or right breath: breath is wrong or right per posture or activity, and it’s very easy to tell just by trying. The ability to breathe fully and strongly in any situation provides tremendous freedom, easily as liberating as that of having muscular strength, or a lot muscular/joint flexibility. Improving yourself on all three accounts is bliss.

As I mentioned before, yoga’s focus is obstruction of the breath, and as such is some of the best training in breathing you can get. Every pose creates its unique challenges; in no two poses do you breathe the same way. In addition to positional relationships of torso and limbs, yoga also employs other muscles to challenge the breath: the sphincter at the bottom of the pelvic floor (mula bandha) and the sphincter in the throat (vocal chords, jhalandara bandha), which all effect the origin and insertion of the diaphragm (which is also, actually, a sphincter: uddiyana bandha). Working these in various configurations of the spine and the diaphragm can make even simple poses into breathing challenges.

(Adapted from Leslie Kaminoff’s work on the Breathing Project