Breathing practices, called pranayama, are an important part of any yoga practice. So if you attend yoga classes, you’re guaranteed to hear the teacher instructing students to control the breath in a variety of ways, some more complicated than others. The most common instructions that I’ve encountered while taking yoga classes are “breathe into your belly” and “breathe into your ribs.”
When I started doing yoga, I found myself confused about the mechanics of these two different actions, which never get fully explained during class (through no fault of the teacher — there simply isn’t time). Rather than simply experiencing the breathing exercise the teacher was offering, I often found myself thinking:
How? How on earth can air move into my belly? Air only goes in and out of the lungs, which are in the rib cage last I checked. What am I missing?
It turns out the answer to that question is pretty simple.
Simple, that is, once you understand some basic principles of breathing, which can get very complicated very quickly. I’ll walk through some of these basics here in order to explain the difference between a “chest breath” and a “belly breath.” Stick with me! And don’t hesitate to ask questions.
The Breath is Both Physiological and Experiential
First, it’s helpful to distinguish two ways that we can evaluate the concept of breathing.
- The breath as a physiological process.
- The breath as something we experience.
Sometimes these viewpoints align and sometimes they don’t — which can create major confusion.
Take this common instruction for example: “Breathe into your belly.”
From an experiential standpoint, this phrase makes sense and may even feel very intuitive. Most of us can feel the abdomen rising and falling while we breathe. Focusing on drawing the breath down into the belly can help some individuals breathe more deeply, smoothly, and/or consciously — all things we generally want to encourage in yoga, which is why this phrase gets used so often.
On the other hand, from an anatomical and physiological perspective, the instruction “breathe into your belly” is a little fuzzy and potentially misleading. As I mentioned, when I started taking classes, I found myself wondering: If air only moves in and out of the lungs, how can you breathe into your belly? What am I missing?
The Difference Between “Air” and “Breath”
One of the things I was missing is the distinction between the concept of air and that of breath. Air is the invisible gaseous substance that moves in and out of the lungs through the bronchial tree during breathing (to be precise). While breath, according to Leslie Kaminoff, “can mean any type of movement . . . that accompanies respiration.”(1)
So even though air doesn’t move into the belly when we breathe, the breath does. This just goes to show how important precision of language is while teaching... At least when you have literal thinkers like me in your class...
OK, so that clears it up somewhat but why exactly does the belly move when we breathe? To answer that question, let’s look at the diaphragm. We’ll get its anatomy out of the way first.
Anatomy of the Diaphragm
The principal muscle of breathing is the diaphragm. It is shaped like a parachute or jellyfish and sits below the lungs. It is tucked under the rib cage and it divides the torso into the thoracic and abdominal cavities.
The outer edge of this “parachute” attaches to the sternum, the base of the rib cage and the front of the lower (lumbar) spine. Together, these points of connection are referred to as the muscle’s origin.
At the top of this “parachute” is a flat surface called the central tendon, made of non-contractile fibrous tissue. This means that it does not contract on its own like a muscle. It can move but only when the muscle fibers that attach to it contract. The central tendon is referred to as the diaphragm’s insertion.
The Diaphragm Contracts on Inhale and Relaxes on Exhale
When the diaphragm contracts, it changes the shape and, more importantly, increases the volume of the thoracic cavity. This increase in volume results in a decrease in pressure within the cavity. This decrease in pressure causes air to flow into the lungs. This is an inhale.
When the diaphragm relaxes, the lung tissues and thoracic cavity spring back to their original shape and volume, expelling air out of the lungs. This is an exhale.
In a relaxed breath (like when we sleep), the exhale is passive — meaning it occurs because muscles relax. That is not always the case when we change or control our breathing while performing physical activities or pranayama (yogic breathing) techniques.
The Movement of the Diaphragm
The muscle fibers of the diaphragm are primarily oriented vertically (up and down).
This means that when it contracts, shortening its fibers, it pulls the central tendon (the insertion) and the base of the rib cage (the origin) toward each other. The “parachute” starts to flatten itself out.
The movement of the breath is directed around the torso based on which part of the diaphragm (the origin or insertion) is stabilized and which part is left free to move. This is the distinction between a “chest breath” and a “belly breath” that you’ve been waiting for!
Chest Breath: The Central Tendon is Stable and the Rib Cage is Mobile
When the central tendon is held in place and the ribs are free to move, the base of the rib cage is lifted toward the central tendon when the diaphragm contracts. This causes the rib cage and thoracic cavity to expand to the sides, front and back. This is thought of as a “chest breath.”
Belly Breath: The Rib Cage is Stable and the Central Tendon is Mobile
When the rib cage is held in place and the central tendon is free to move, the central tendon is pulled downward toward the base of the rib cage when the diaphragm contracts. This presses down on the abdominal cavity.
We’ve already established that the thoracic cavity changes in shape and in volume during breathing, which is how air is drawn into and expelled out of the lungs. The abdominal cavity, however, only changes in shape during breathing.
Leslie Kaminoff compares the abdominal cavity to a water balloon to make this point.(2) When you squeeze one end, the other end bulges. The shape changes and the contents are shifted around but the volume stays the same. (Note that the abdominal cavity can change in volume in other ways not associated with breathing, like when you eat a big meal or become pregnant.)
When the diaphragm presses down on the abdominal cavity, making room for the thoracic cavity and thus lungs to expand, the organs are essentially pushed out of the way and the belly bulges like a water balloon. This is thought of as a “belly breath.”
Every Breath is a Diaphragmatic Breath
So there you have it. Once you understand the diaphragm as a muscle that can be stabilized on one end and allowed to move on the other, the “why” behind chest and belly breathing becomes pretty straight-forward.
It’s helpful to note that the scenarios described above are the two extremes. They can happen independently or they can both happen at the same time to varying degrees. It depends on the activity of two groups of muscles called the accessory muscles of respiration and the postural stabilization muscles in the torso.
One last thing I’d like to emphasize is that the diaphragm is always acting when we breathe. You’ll sometimes hear belly breathing referred to as “diaphragmatic breathing,” implying that you’re not using your diaphragm if you breathe into your ribs, but in fact every breath is a diaphragmatic breath. One’s breathing pattern might be efficient or inefficient, but it always involves the contraction (on inhale) and relaxation (on exhale) of the diaphragm.
The diaphragm’s main function is to draw air into the lungs by increasing the volume of the thoracic cavity. It does this in two ways:
- The diaphragm lifts the base of the rib cage and sternum, expanding the rib cage to the front, sides and back, creating a “chest breath.”
- The diaphragm presses downward on the abdominal cavity, which bulges forward, creating a “belly breath.”
For more information on this and other misconceptions about breathing, check out the articles linked below.
(1) Leslie Kaminoff, “Breath Flow in Yoga Practice.” http://www.yogaanatomy.org/2001/breath-flow-in-yoga-practice-3/
(2) Leslie Kaminoff, “What Yoga Therapists Should Know About the Anatomy of Breathing.” http://www.yogaanatomy.org/wp-content/uploads/2011/10/Anatomy-of-Breath2.pdf