In the 6th century C.E. in China, the Buddhist monk Fuxi wrote:
The 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 (1)
Another translation:
The handless hold the hoe.
A pedestrian walks, riding on a water buffalo.
A man passes over the bridge;
The bridge (but) not the water flows. (2)
I would say “the empty hand grasps the hoe handle” is a reference to the role of ligaments at the sacrum in activity related to posture. Here’s a summary of a study that confirms that some of the activity of the lower body is “regulated” by the iliosacral ligaments:
This study (research by Indahl, A., et al.) established that the ligamento-muscular reflex existed between the sacroiliac joint and muscles that attach to the bones that make up the sacroiliac joint. (The study’s authors) suggested that the sacroiliac joint was a regulator of pelvic and paraspinal muscles and, thereby, influences posture and lumbar segmental stability. (3)
There’s a phenomena called “reciprocal innervation” that can enter into the activity of posture. I first read about “reciprocal innervation” in the writings of Dr. John Upledger, in a description he gave of his experience lying on salt water in an isolation tank:
At some point my body began to make fish-like movements, as though my pelvis and legs were the lower part of a fish moving its tail from side to side. This movement was nice and easy. The neurophysiologist in me related these movements to an expression of what we call ‘reciprocal innervation’. The principle here is that, when your trunk is bent to the side in one direction past a certain threshold, the muscles on the other side of the trunk contract. In doing so, the nerve impulses are diverted from the side to which you are bent, and those muscles relax. Your trunk now bends in the opposite direction until that side-bending threshold is passed. The nerve impulses are then diverted again to the opposite side, causing muscle contraction and side bending in that direction. (4)
In a seated posture, reciprocating activity in the muscles of the legs can feel like walking, with the reciprocity controlled by the stretch of ligaments between the sacrum and the pelvis: “walking along, I ride the ox”.
The stretch allowed by a ligament is slight (less than 6% of the total length of the ligament (5)), and yet as the study by Indahl and associates showed, even a slight stretch can influence muscular activity.
I think it’s possible that a “ligamento-muscular reflex” also exists between the intervertebral ligaments of the spine and the muscles of the abdomen and lower back.
I have read that a reference to a “wooden bridge” in Fuxi’s day was really a reference to a log across a stream. However, I’m not able to confirm that explanation; neither do I see any reference to “wood” or “wooden” in any of a dozen other translations of the poem (6).
The second translation I quoted above renders the third line:
A man passes over the bridge
To me, the characterization of what passes over the bridge as “a man” speaks to a particularly human balance. I have written previously about Gautama’s analogy for the third state of concentration (white, red, and blue lotuses that never break the surface of a pond (7)). I believe Gautama’s analogy refers to the balance of the legs, arms, and head around the place of occurrence of consciousness. I would say “a man passes over the bridge” is an allusion to such a balance, with the place of occurrence of consciousness being the bridge.
The last line of the poem is:
The bridge is flowing, the water is still
The place where consciousness occurs suddenly becomes the source of action of the body, the place seeming to flow from moment to moment, while action based on volition or habit ceases entirely, or falls still.
2) Ch’an and Zen Teaching, Series One by Lu K’uan Yü (Charles Luk); Rider & Co., London, 1960, p. 143-145; Translated from The Imperial Selection of Ch’an Sayings (Yu Hsuan Yu Lu) [Yuxuan yulu (Imperial Selections of Recorded Sayings / Emperor’s Selection of Quotations)].
3) Serola Biomechanics website summary of Indahl, A., et al., Sacroiliac joint involvement in activation of the porcine spinal and gluteal musculature. Journal of Spinal Disorders, 1999. 12(4): p. 325-30; https://europepmc.org/article/med/10451049,
https://www.serola.net/research-category/the-nutation-lesion-2/ligamento-muscular-reflex/.
4) “Your Inner Physician and You: Craniosacral Therapy and Somatoemotional Release”, John E. Upledger, p. 165; see also “Reciprocal Innervation and Symmetrical Muscles”, Professor C. S. Sherrington, University of Liverpool, Nov. 13, 1912.
5) https://web.mit.edu/tkd/stretch/stretching_3.html.
6) “Zen Literature” on Terebess, https://terebess.hu/zen/fuxi.html.
7) see “Applying the Pali Instructions”.