The Psoas muscle is often referred to as the deepest core muscle in the abdominal canal. The muscle affects pelvic and hip stability, structural balance and flexibility. It is the bridge linking the trunk of the body to the legs, which is important in keeping us upright and moving.
Dr. Ida P. Rolf described the role of the psoas in walking:
Let us be clear about this: the legs do not originate movement in the walk of a balanced body; the legs support and follow. Movement is initiated in the trunk and transmitted to the legs through the medium of the psoas. (Rolf, 1977: Rolfing, the Integration of Human Structures, pg. 118).
In fact, the psoas muscle affects every facet of our life, from a physical well-being, to who you believe yourself to be and how you relate to the world.
Whether you suffer from low back pain or anxiety, knee strain or exhaustion, likely the psoas muscle is a contributing factor to the issues. Awareness of this muscle may not be as easy to feel, unlike the biceps or hamstring muscles; but improving awareness to the psoas muscle can greatly enhance your physical and emotional health.
Developing an increased awareness of this critical muscle may unlock deep rooted fears in the body that were stored unconsciously in physical tension. Intimately involved in the stress response - fight/flight/freeze response- the psoas can curl you into a protective fetal ball or prepare you to run.
Over time, a chronically tight psoas muscle will cause the body to continually feel the signals of danger, thereby exhausting adrenal glands and decreasing the immune system. These are two other systems involved in the stress response.
As you learn to approach the world with less chronic stress, less fear, the psoas awareness can open the door to a more sensitive attunement to your body's inner signals about safety and danger and enhance a greater sense of inner peace.
Attachment of the psoas muscle originates from the 12th thoracic vertebrae and each five lumber vertebra, moving through the pelvis with iliacus, inserting as a common tendon to the trochanter of the femur. It guides the transfer of weight from the trunk to the legs for movement and helps to stabilize the spine. In addition, the psoas muscle provides a diagonal support through the trunk, acting like a "hammock" for the vital organs. When walking, a healthy psoas moves freely with a relaxed diaphragm, massaging organs, increasing circulation and flow of fluids.
The amount of time you spend sitting in a day, incorrect postures during exercise, poor diet, abdominal tensions and incorrect sleep positions, all contribute to the shortening of a psoas muscle.
Therefore it is important to learn to manage fearful stress responses appropriately. You must relax and breathe into the lower abdominal area, so as to stretch the psoas in movement, which will help to build muscle memory and strength, allowing for spine stability.
Liz Koch's, The Psoas Book is an excellent resource to understanding this crucial muscle function and how best to manage the function of the psoas muscle.