The thoracic (breathing) diaphragm is a broad, thin, double domed muscle with insertions around the circumference of the lower rib cage, the spine, and the lower portion of the sternum. It spans the thoraco-abdominal cavity and contains a strong central tendon, the left and right parts of which insert into one another. The thoracic diaphragm is the main muscle of the breath, and it is said that its movement is responsible for 75% of the respiratory airflow. The accessory breathing muscles are responsible for the additional 25%.The diaphragm separates the heart and lungs above from the abdominal organs below. The heart rests on the central tendon and is connected to it by the pericardium. The heart rises and falls with the movement of the diaphragm, as do the lungs. The diaphragm is the seat of the heart and lungs. It massages, rolls, and squeezes the abdominal organs as it moves. This movement contributes to health and suppleness in the organs as they are bathed in fresh blood and fluids. An under-recognized and under used aspect of the diaphragm is its muscular stem. The stem, or crura, is widely considered to connect only about as far as the third lumbar vertebra; however, in Embodyoga® and Body-Mind-Centering® we have found that in full use, the support of the stem can be felt all the way to the coccyx. We feel it is important to develop the use of the diaphragm all the way to the tail because we consider it to be the primary muscular support of the lumbar spine. The stem of the breathing diaphragm blends with the anterior longitudinal ligament along the front of the spine. The effect of this muscular and ligamentous support along the front of the spine through the lumbar region is absolutely critical to full integration of upper and lower body in asana. Without the use of this strong vertical support there is often a break in the pranic flow from head-to- tail and tail-to-head. This effects our experience of “integration and unity” in the posture and compromises the integrity of the spine in the bargain.
The stem also roots the breath all the way through to the tail and into the pelvic floor. This connection is extremely important because the movement of the thoracic and pelvic diaphragms is coordinated in full breathing.You may imagine the stem of the diaphragm to be like kite strings. The kite rides on the wind, but without its tether to the earth it would simply blow away. Or, the diaphragm may feel like a mushroom with a stem, or an open umbrella with a soft, strong hand on the handle. Focusing on such imagery may or may not be helpful to you. Perhaps you would rather feel the thoracic diaphragm as it is and work directly with the body tissues. There are many ways to enter this inquiry more deeply. No one way is better than another and whatever is most helpful for you is fine. The pelvic diaphragm is also extremely important in full breathing. If the thoracic diaphragm is not connected via its stem to the pelvic diaphragm, full breathing is restricted. The ways in which we move and breathe govern how our tissues develop and maintain their integrity. Lack of use can cause muscles to atrophy. As members of a culture with a predilection for sitting in chairs, we tend not to make use of the stem of the diaphragm. Sitting in chairs for most of our lives causes disruption in the movement of forces through the weight bearing bodies of the vertebrae and interrupts the flow of breath and structural support along the stem of the breathing diaphragm to and from the tail. These patterns of disconnection are so strong in us, and are reinforced so often, that even when we practice yoga it is entirely possible that we will continue to practice unhealthy breathing and movement patterns. Tissues develop through use. By changing the way we use our breathing diaphragm we can enhance its functions and create better integration for movement and breath. One of the keys to using the breathing diaphragm more effectively can be to inquire into, and practice with, the Calm and Mobile Spine principle. As we learn to maintain our head-to-tail and tail-to-head connection, we will begin to heal the energetic breaks along our core and the natural muscles of support will come into play appropriately. Also, we can use our imagination and visualization skills to begin to penetrate more deeply and increase our inner awareness. For example, we can imagine what it might be like to have the sensation of muscular tone running all the way down the spine, from the diaphragm to the tail. We can move and breathe with an inquiry into that possibility. In this way, we can begin to take steps toward not restricting the range of our breath, and we can set up new ways of moving that do not disrupt the flow of forces through our core.