Attend to the Breath Part 3: Mechanics

by Kerry Porter Wills

profilekw2My central intent in writing this piece is to have you PAY ATTENTION to two obvious facts. The first is that we have some choice with our breath. We can lengthen, shorten, hold and release with some degree of accuracy and with training, we can maximize these possibilities. In so doing, we give our systems more choices in how they adapt to the demands on them. We give ourselves a conscious way of perceiving and managing our internal states.

Breath training generates information which we need in order to make more conscious choices. So that’s the first half of it. The second half of it is to state the obvious again, which is that there is a limit to our ability to choose what is happening with the breath. In other words, your body will breathe without your conscious input. Here is a simplified description of the process at the autonomic level:

The impulse to inhale arises when the carbon dioxide receptors sense there is too much CO2 in the blood. The receptors signal the phrenic nerve to fire the diaphragm.

Photo credit: Image from Yoga Anatomy, by Leslie Kaminoff and Amy Matthews, used by permission.

Photo credit: Image from Yoga Anatomy, by Leslie Kaminoff and Amy Matthews, used by permission.

The diaphragm is the principal muscle of 3-D shape change, i.e. breath (see part 1 where breath is defined as the shape change of the abdominal and thoracic cavities). When the diaphragm contracts, it lifts and spreads the ribs which is where large portions of it are attached. Note: this is just one possible shape change that produces an inhale.

This lifting and spreading of the ribs increases the volume of the thoracic cavity, which causes the pressure in that cavity to drop (there is an inverse relationship between volume and pressure). It’s this inverse relationship that creates the pressure differential between the inside and outside of your system that gets the air into your lungs.

When the pressure INSIDE the thoracic drops below the pressure OUTSIDE the thoracic, that differential is resolved by air molecules flooding the lowest pressure zone inside your lungs. The weight of the air around us PUSHES air into our lungs as the thoracic pressure decreases. This process is self-regulating in that the pressure differentials inside and outside the system are continually being resolved by volume changes, inhale followed by exhale followed by inhale until we die.

The contraction of the diaphragm lifts and spreads the ribs, creating a volume and pressure change, air flows in, and then the diaphragm relaxes. It just relaxes, i.e. passive recoil. This will reverse the shape change of the inhale, such that the rib cage drops in and down, which reduces the volume of our thoracic cavity, pressure goes up and air leaves the lungs.

In breath training we learn (1) to manipulate the process of shape change such that many of the variables above can be sensed and re-patterned when appropriate, (2) to become aware of the process as it arises in an un-manipulated way, and (3) to better understand and utilize the dance between (1) and (2).

For more information on the breath, go to The Breathing Project and Yoga Anatomy online. Also see Part 1 and Part 2 of these series for some exercises which can help integrate these concepts through experiential awareness.

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