Full body breathing is an extraordinary symphony of both powerful and subtle movements that massage our internal organs, oscillate our joints, and alternately tone and release all the muscles in the body. It is a full participation with life.
- Donna Farhi, The Breathing Book
Breathing is a simple act we have performed since the moment we were born, but for many of us only becomes illuminated within our yoga practice. We might go all day without noticing our breath until the moment we come to the mat – and observe. Of all the functions of our body, the act of breathing is one of the most fascinating. It is completely subconscious yet we can exert conscious control. It is a muscular act, yet one also controlled by the laws of science that govern molecules of gas. It sustains our life, nourishes our organs, helps expel waste from our body, and can affect our emotional state by acting on our nervous system. Understanding exactly how our body performs this extraordinary act can bring us deeper into our pranayama (breathing) practice.
The Path of the Breath
As we breathe in through the mouth and nose, air flows into our trachea (windpipe) and divides into tree-like right and left bronchi and into the lungs into smaller branching bronchioles. These end in alveoli which are the main site of oxygen and carbon dioxide gas exchange. The lungs are actually dense, sponge like organs that extend from just above our clavicle (collarbone) to our lower ribs. Our right lung is larger than our left due to the close proximity of the heart to the left lung.
The driving force behind our breath is one of the most important muscles in the body: the diaphragm. It is a dome shaped muscle that attaches from our sternum (chest bone) at the front, wrapping around the inside of our lower ribs seven through twelve, and to our spine via finger like projections to L1-4 vertebrae. It separates the organs of our chest from our abdominal and pelvic organs. It also has openings for blood vessels to travel through as well as two muscles: the quadratus lumborum and the psoas muscle. This close relationship with two important muscles of the lower back and pelvis may partly explain why people with low back pain have altered breathing patterns.
As we inhale the diaphragm lowers, and as we exhale the diaphragm relaxes and rises up. This affects the volume of the thoracic (chest) and abdominal cavities, and in turn the pressure of the oxygen and carbon dioxide molecules. Gases always fill their container. In a large space the molecules are far apart therefore the pressure is low. Much like a busy yoga class, in a small space the molecules are close together so the pressure is high. Since gases flow down a pressure gradient from high to low, when the thoracic cavity volume increases, the pressure decreases and causes air to rush in from the atmosphere. The dimensions only change a few millimeters but it increases the volume of the thoracic cavity by almost half a liter. Inspiration ends when the pressure in the lungs matches the pressure in the atmosphere. On exhalation the diaphragm and other muscles of breathing relax, the lungs recoil, thoracic volume decreases compressing the alveoli and the pressure in the lungs rises again, which forces gases to flow out of the lungs.
You can experience this action on yourself. Place one hand on your upper belly, just below your sternum. As you inhale, notice how your abdominal organs depress and your belly widens as your diaphragm drops down. As you exhale observe the diaphragm rising and your belly resuming its natural position. This natural phenomenon is what your yoga teacher may refer to as belly breathing. In our culture of tummy sucking in, this feeling of letting the stomach expand may feel foreign or require some practice to access.
It Takes a Village
Although the diaphragm is the main muscle of breath, and gas exchange encourages the diaphragm to contract, there are also accessory muscles of breathing that enable movement of the rib cage and sternum essential to the breath. The 12 pairs of ribs attach at the spine to the corresponding numbered thoracic (mid-back) vertebrae. Ribs one through seven wrap around and attach to the sternum. Ribs 8, 9, and 10 are shorter and don't quite make it all the way around to the sternum so attach at the front to the rib above. Ribs 11 and 12 are known as floating ribs since they have no attachments to the front of the body. Between each rib are intercostal muscles which enable the sternum to move up and out on an inhale, and the ribs to expand 360 degrees in a bucket handle pattern. (Imagine the handle of a bucket resting on a pail. If you were to pick up the bucket, the handle would rise in an arc.)
To experience this phenomenon on yourself, place your hands on the sides of your lower ribs. As you inhale, notice the rib movement not only up but also outwards in all directions. Next wrap your arms around yourself in a hug to feel your upper ribs near your scapula (shoulder blades). Inhale and feel the back of your body expand as your ribs move. We often only think of breath flowing in the front of our body but our back body also moves as the breath moves.
The act of breathing is not only essential to life; it can be a transformative part of our yoga practice. It can allow us to go deeper into a pose or go deeper into relaxation. It can enable us to let go of distracting thoughts or emotions and make space for positive or calming ones. Understanding the anatomy of our pranayama practice can bring the practice to life, allowing us to picture the miracle that is occurring inside our bodies as we flow to our own individual rhythm of breath.