The reciprocal innervation of the extensor and psoas muscles results in an upright posture, yet the action of these muscle groups also tends to rock the pelvis on the hips and on the sacrum. The largest fascial connections in the body lie between the pelvis and the sacrum, and the length of the spine can serve as a lever to initiate stretch in these joints.
In the fifth century of the common era, a Buddhist monk named Fuxi wrote a description of the experience of meditation, as follows:
An empty hand grasps the hoe handle
Walking along, I ride the ox
The ox crosses the wooden bridge
The bridge is flowing, the water is still.
(“Zen’s Chinese Heritage”, Andy Ferguson, pg 2, ©2000 Andrew Ferguson)
The reciprocal activity of the extensor and psoas muscles becomes “an empty hand” at the sacrum, as the contraction and relaxation of the psoas muscles aligns the hips and shifts the pelvis on the joints with the sacrum.
The ability of the extensor and psoas muscles to stretch the fascia between the pelvis and the sacrum depends in part on support for the lower spine generated in the movement of breath. In exhalation, the rearward inclination of the spine stretches a set of horizontal ligaments between the lowest vertebrae of the spine and the pelvis; in inhalation, the forward inclination of the spine stretches a set of vertical ligaments between the second-lowest vertebrae of the spine and the pelvis. As the two sets of ligaments are alternately stretched with the movements of the body in inhalation and exhalation, the motion of the lower spine is supported, and movement at the sacrum without compromise to the integrity of the lower spine becomes possible.
In the second line, Fuxi describes a feeling in the legs like that of walking. With the stretch of the fascia between the pelvis and the sacrum, and with the support for the lower spine generated in the movement of breath, a freedom of motion develops at the sacrum. As the motion of the sacrum stretches the fascia between the sacrum and the pelvis in the three directions, feeling is realized for activity in the legs connected with the upright posture, activity that resembles the activity of the legs in walking.
Because the feeling in the legs depends on the free movement of the sacrum, and the free movement of the sacrum depends on the stretch of ligaments between the pelvis and the lower spine, the activity like walking in the legs carries into the activity in the lower back and abdomen as the breath moves in or out. Just as a stretched piece of string can carry the sound of a voice from one tin-can to another, the activity in the legs can carry through the ligaments between the pelvis and the lower back to resonate in the upper body.
As the activity in the legs and in the lower back opens feeling in the pelvis, more specific feeling for the stretch of the ligaments between the sacrum and the sit-bones can be realized, and the activity generated side-to-side by that stretch can be relaxed. Fuxi described this in his poem with the words, “I ride the ox”.
The activity side-to-side in the pelvis opens the hips and allows the pelvis to turn slightly around the hips. The turning motion stretches ligaments between the sacrum and the bottom-front edges of the pelvis on either side; activity generated by the stretch of these diagonal ligaments rotates the sacrum contrary to the motion of the pelvis, using muscles that connect the upper legs directly to the sacrum under the sides of the pelvis. The impact of the contrary motion on the fascia around and behind the sacrum generates activity in the extensors, upward along the spine.
The feeling of the motion generated by the activity under the pelvis to the sacrum is described in the line, “The ox crosses the wooden bridge”. Fuxi specifies that the bridge the ox crosses is a wooden bridge; that’s because the fascia under the pelvis and behind the sacrum reverberates at the extremums of motion generated by the cranial-sacral rhythm, just as a wooden bridge resounds with the step of an ox.
The motion in a narrow range at the sacrum that travels up the extensors can move the bones on either side of the skull. Nerves at the top of the skull respond to pressure from these bones, as they regulate the volume of fluid in the cranial-sacral system. The changes in the rhythm of the cranial-sacral fluid can alter the movement of the sacrum on the pelvis, and affect the stretch that generates activity in the extensors. In this way, movement at the sacrum and changes in the cranial-sacral rhythm can feed back on one another, while the breath moves in or out.
“The bridge is flowing, the water is still”: reverberation in the stretch that is already in existence flows with the feeling of place in the contact of sense. Through the flow of reverberation, the occurrence of consciousness acts to effect feeling, posture and movement, and all intentional activity ceases.
In his poem, Fuxi described four distinct experiences. The transition from one experience to the next may depend on a phenomena of the cranial-sacral system that Upledger referred to as a “still point”; when a “still point” occurs, the rhythm of the cranial-sacral system ceases momentarily and the fascial support throughout the body somehow rearranges. The “still point” can be encouraged through a slight extension maintained in the bones on the centerline of the skull, but the actual occurrence of a “still point” apparently depends on the inner need of the individual.
No training or particular posture is required to have an experience like those Fuxi described in his poem. That said, the rhythm of the cranial-sacral system at the sacrum is the engine that drives experiences like those Fuxi described, and the lotus posture is particularly suited to the isolation of the cranial-sacral rhythm at the sacrum.