Cheng Man-Ch’ing gave his students some advice for the practice of T’ai Chi:
… The whole body’s weight rests on only one leg. If two legs equally carry it, this is double-weightedness. When the weight is transferred, the sacrum and the upper back must be kept upright in the middle. Then you will not lose your equilibrium.
… The key point of transfer of strength from the right hand to the left hand is in the upper back, and the key point in the transference of strength from the left leg to the right is in the sacrum. The sacrum and the upper back must be straight and upright. Then you will not lose equilibrium.
When you practice, the occipital bone (at the back of the skull) should be upright. Then the shen (spirit) and the ch’i (breath or breath energy) reach the top of the head.
“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, pp 89-90; parentheticals added)
Cheng’s advice to keep the sacrum, the upper back, and the occipital bone “upright” may have to do with the stretch of fascia behind the sacrum and spine, and the engagement of ligaments.
Activity in the muscles that arch the spine rearward, the extensor muscles, can effect a stretch of the fascia behind the sacrum. As H. F. Farfan wrote:
There is another peculiarity of the erector muscles of the spine. Below the level of the fifth lumbar vertebra, the muscle contracts in a compartment enclosed by bone anteriorly, laterally, and medially. Posteriorly, the compartment is closed by the lumbodorsal (thoracolumbar) fascia. When contracted, the diameter of the muscle mass tends to increase. This change in shape of the muscle may exert a wedging effect between the sacrum and the lumbodorsal fascia, thereby increasing the tension in the fascia. This may be one of the few instances where a muscle can exert force by pushing.
(“Mechanical Disorders of the Low Back”, H. F. Farfan; 1973 Lea & Febiger; p 183; parenthetical added)
The increased diameter of the contracted extensors and the stretch of the thoracolumbar fascia may also exert force on the bones of the sacrum, and stretch the ligaments that connect the sacrum to the pelvis. Research indicates that stretch in the sacroiliac ligaments can regulate the activity of muscles in the vicinity of the sacrum:
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.
(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; europepmc.org/article/med/10451049,
serola.net/research-category/the-nutation-lesion-2/ligamento-muscular-reflex/; parentheticals added)
The paraspinal muscles are the muscles that run vertically along the spine.
Researchers have now concluded that the transverse and oblique abdominals can engage with the muscles of the spine and with the thoracolumbar fascia behind the spine to support the joints of the spine between the sacrum and the thorax:
Stability and mobility are opposing states in joints. To stabilize the lumbar spine, especially between L1 and L4 levels without ribs, the transverse abdominus and internal oblique muscles and their fascial aponeurosis (attachments) resemble a flexible myofascial ring between the thorax and pelvis. … This axial abdominal–lumbar myofascial ring, between the thorax and pelvis, generates muscles contraction to compensate for the lack of rib stability. … The present study has demonstrated that co-contraction of the paraspinal muscles and the deep abdominal muscles is capable of creating this girdling effect.
… Using a biomechanical model, Hukins et al. (1990) showed that limiting radial expansion of the PMC (paraspinal muscular compartment) due to contraction of the deep abdominal muscles could increase the tension within the TLF (thoracolumbar fascia) compartment by 30%, leading to a proportional increase in the extensor moment exerted by paraspinal muscles….
(“The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia”; A Vleeming, M D Schuenke, L Danneels, F H Willard; J Anat. 2014 Aug 20;225(4):447–462. doi: 10.1111/joa.12227; parentheticals added)
The authors of the study cited the “myofascial ring” between L1 and L4 as the source of muscle contraction in the abdomen and lower back, though they gave no references for their assertion. There is, however, an apparent “ligamento-muscular reflex” between the ligaments of the spine and the associated paraspinal muscles, like that reported by Indahl and associates in connection with the sacroiliac ligaments:
In 1998, Stubbs, Harris et al. established the presence of a ligamento-muscular reflex from the mechanoreceptors in the lumbar supraspinous ligament to adjacent paraspinal muscles. Although done with electrical stimulation, they found that the contracted muscles, by creating an extension response, relieved tension on the ligament that would be strained by flexion.
(Serola Biomechanics, serola.net/research-category/the-nutation-lesion-2/ligamento-muscular-reflex/; Stubbs, M., et al., Ligamento-muscular protective reflex in the lumbar spine of the feline. J Electromyogr Kinesiol, 1998. 8(4): p. 197-204)
That suggests that the source of the muscle contraction in the “myofascial ring” is a ligamento-muscular reflex generated by ligaments in the lower spine, a reflex that triggers reciprocal innervation in the ring between the paraspinal muscles and the transverse and internal oblique muscles of the abdomen.*
The sacrotuberous, sacrospinous, and iliolumbar ligaments are also likely to generate reflex muscular activity, although that has yet to be established. Such activity might be expected to result in muscle contraction and reciprocal innervation in the pelvic basin.
In the 1950’s, D. L. Bartilink’s experiments established that in weight lifting, support for the integrity of the lower spine comes in part from the pressurization of “the abdominal fluid ball” by the transverse, internal oblique, and external oblique muscles.
In addition to bearing some of the load that would otherwise compress the annuluses of the spine, the “fluid ball” exerts a pressure to the rear that can displace the thoracolumbar fascia behind the lumbar spine, and thereby support the spine (Gracovetsky, Farfan, and Lamay, 1977).
Dr. Rene Cailliet provided a summary of the finding:
… the abdominal pressure is considered to be exerted posteriorly against the lumbodorsal (thoracolumbar) fascia, causing the fascia to become taut…. thus relieving the tension upon the erector spinae muscles.
(“Low Back Pain Syndrome”, ed. 3, F. A. Davis Co., pp 140-141; parenthetical added)
The support of the thoracolumbar fascia and ligaments is crucial in weight-lifting:
It is essential that the supraspinous ligament and the lumbodorsal (thoracolumbar) fascia be brought into action to permit weight lifting without disk or vertebral failure…
(Gracovetsky, S., Farfan HF, Lamay C, 1977. A mathematical model of the lumbar spine using an optimal system to control muscles and ligaments. Orthopedic Clinics of North America 8: 135-153)
The ligaments have a weight-bearing capacity that far exceeds that of the muscles:
It must be kept in mind that in some circumstances ligament tension may reach 1800 lb., whereas no muscle can pull as hard.
(ibid)
I have illustrated the mechanisms of displacement of the thoracolumbar fascia, both behind the sacrum and behind the spine:
Although seldom noted in the literature, alternation in the activity of the extensor muscles has been observed, particularly in the lower spine:
The alternating activation between sides of lumbar muscles was similar in patients with cLBP (constant low back pain) compared to HCs (healthy controls). … The exact mechanism for alternating activation is not clear…
(“Reduced muscle activity variability in lumbar extensor muscles during sustained sitting in individuals with chronic low back pain”, doi.org/10.1371/journal.pone.0213778; emphasis in title added)
Cheng Man Ch’ing asserted that straightening the occiput bone allows the shen (spirit) and the ch’i (“breath energy”) to reach the top of the head. He quoted an instruction from the Classics:
Raise the strength to the top of the head.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 89)
If strength is raised to the top of the head, said Cheng, “the energy at the erect top of the head is light and agile.”
The T’ai Chi Classics describe a “light and agile” feeling in the body as a whole, obtained through a particular relaxation:
Relax the inner abdomen, then the whole body is light and agile.
(ibid, p 25)
The “light and agile” feeling may result from an interchange between pressure in the abdominal cavity and the movement of the brain in the skull, an interchange that could involve the angle of the sacrum, the angle of the upper back, and the angle of the occiput:
Specifically, brain motion was driven by abdominal muscle contractions that activate a hydraulic-like vascular connection between the nervous system and the abdominal cavity, and could similarly be induced by pressure applied to the abdomen. … These results suggest that the brain is linked mechanically to the abdominal compartment, and that fluid flow in the brain could be coupled to body movements.
(Gut-Brain Hydraulics: Brain motion and CSF circulation is driven by mechanical coupling with the abdomen, doi.org/10.1101/2025.01.30.635779)
The contribution of upright posture to the stretch of fascia and the moment of extensors, not only behind the sacrum but behind the upper back and the occiput as well, could be a factor in the ease of the vascular connection between the abdomen and the brain.
Movement in T’ai Chi Ch’uan is said to result from the mobilization of ch’i. The mobilization of ch’i, meanwhile, depends on the accumulation of ch’i at a location in the body called the tan t’ien.
Cheng described the tan t’ien as “the only path for the Taoist”:
… the tan t’ien in T’ai Chi Ch’uan is the only path for the Taoist; there is no other way. The tan t’ien lies in the abdomen close to the navel and goes back toward the spine. It is located about 1.3 inches below the navel. In physiology it is referred to as the center of gravity of the body, and is located in the middle of the waistline.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 95; emphasis added)
Cheng outlined a method for the cultivation of ch’i at the tan-t’ien:
To cultivate the ch’i it is necessary to sink the ch’i to the tan t’ien.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 61)
To sink the ch’i is to will the ch’i to accumulate in the tan t’ien, but not to stuff the abdomen. Be careful!
(ibid, p 106)
If those who learn T’ai Chi Ch’uan do not know what Mencius meant by “Seek the released mind,” they will find that their cultivation of ch’i is meaningless and simply tiresome. The Classics say that the mind and ch’i stay together in the tan t’ien. This is the “seeking of the released mind” to arrive at the perfect place of cultivation without harm.
(ibid, p 59; emphasis added)
With regard to the mobilization of ch’i, Cheng again quoted the Classics:
The Classics say, “The mind mobilizes the ch’i and the ch’i mobilizes the body. The ch’i spreads throughout the whole body.”
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 32; emphasis added)
In Cheng’s teaching, the ch’i is cultivated at the tan t’ien together with the “released mind”, yet at the same time the mobilized ch’i spreads throughout the body. In Gautama the Buddha’s teaching, a person “lays hold of one-pointedness” of mind and gathers zest and ease together in “one-pointedness”, yet at the same time zest and ease are extended throughout the body.
Gautama provided a metaphor:
… just as a handy bathman or attendant might strew bath-powder in some copper basin and, gradually sprinkling water, knead it together so that the bath-ball gathered up the moisture, became enveloped in moisture and saturated both in and out, but did not ooze moisture; even so, (a person) steeps, drenches, fills, and suffuses this body with zest and ease, born of solitude, so that there is not one particle of the body that is not pervaded by this lone-born zest and ease.
(AN 5.28, tr. Pali Text Society vol. III pp 18-19)
Feeling that is extended throughout the body yet gathered into “one-pointedness” can cause the successive occurrences of “one-pointedness” to become contiguous, and can cause reflex activity of the consciousness-informed body to become continuous (see Just to Sit).
In T’ai Chi, the mobilization of ch’i throughout the body and the simultaneous accumulation of ch’i in the tan t’ien serves to make the instances of “the released mind” contiguous, and the movements of the body continuous:
T’ai Chi Ch’uan’s other name is Ch’ang Ch’uan (Long Boxing) because it is like a long river or ocean rolling on unceasingly. This describes the inherent continuity which is the concentration of ch’i and the embodiment of suppleness.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 37)
Cheng also wrote:
The ch’i can mobilize the body, but you need not will the ch’i in order to move it. The spirit can carry the ch’i with it.
(ibid, p 80)
To excite the ch’i means not only to stimulate one’s own ch’i but to join one’s ch’i to the ch’i of Nature so as to reinforce each other. Then it is excellent.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 209)
In a similar vein, Gautama spoke of feelings of benevolence extended through “the whole world everywhere, in every way”, and of concentrations that occur based on “the heart’s release” through the extension of such feelings.
Cheng described the final stage of attainment of T’ai Chi Ch’uan as shén míng, or “spiritual brightness”, arrived at through “t’ing chin”, listening to or feeling (ligamentous) strength, and “tung chin”, the comprehension of (ligamentous) strength.**
Cheng stated, however, that the only skill in T’ai Chi Ch’uan that was difficult for him to learn was chieh chin, or “receiving chin”:
From familiarity with the correct touch you will learn to t’ing chin [listen to strength] . After learning to t’ing chin, you will gradually comprehend tung chin [understanding strength]…. I followed Professor Yang for seven years and only one chin was difficult to learn. It was chieh chin [receiving chin]…. Besides chieh chin there is nothing else.
(ibid, pp 204-205)
The ability to absorb an opponent’s blows, to chieh chin or “receive chin”, depends on the abdomen.
This is the primary reason to use the term “T’ai Ch’i” to name this martial art, for it means to cause the attacking force to dissolve in emptiness. When the opponent realizes that he has failed, his only option is to withdraw and try to escape. During the opponent’s withdrawal of his attacking force, my abdomen, which has absorbed and stored the force of his attack, uses this power to attack his retreat.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, p 49)
Ch’eng explained fa chin, or the discharge of the force of an opponent’s attack:
Chin (strength) comes from the ligaments… What is fa chin (discharging chin)? It is like shooting an arrow. Shooting an arrow depends on the spring force of the bow and string. The force of the bow and string is soft, lively, and flexible.
(“Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan”, Cheng Man Ch’ing, tr. Benjamin Pang Jeng Lo and Martin Inn, pp 91-92)
Like the stretch of a bow string, even the resting alternation of the extensors may be felt in the stretch of the thoracolumbar fascia from the tailbone through the occipital bone, at the soles of the feet and in the movement of air through the sinuses.
The absorption of an opponent’s ligamentous strength apparently depends on the passage of the force through the “fluid ball” of the abdomen to the fascia and ligaments of the lower spine and sacrum. The opponent is then “discharged” through a ligamento-muscular reflex generated from where the strength was absorbed. Cheng wrote:
When you discharge others, it is like cleanly releasing an arrow from a bowstring.
(ibid, p 213)
Cheng offered one last tip for the practice of Tai Ch’i:
The turning of the millstone represents the turning of the waist. “The axle not turning” is equivalent to the equilibrium that comes from the sinking of the ch’i to the tan t’ien.
“The millstone turns but the axle does not turn” is really the transmission of the family secret. … Since I learned this I find improvement every day.
(ibid, p 90)
*Here’s Dr. John Upledger’s description of an experience of reciprocal innervation he had while 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.
(“Your Inner Physician and You: Craniosacral Therapy and Somatoemotional Release”, John E. Upledger, p165)
**Anthropic’s “Claude” assisted me with finding the Chinese words translated as “omnipotence” by Lo and Inn, and as “perfect clarity” by Doug Wile. “Claude” determined that the Chinese words were shén míng, and “Claude” translated the words as “spiritual brightness”.