The "Qi" in Tai Chi: From the extensive discussions on "qi" in ancient Tai Chi boxing manuals, it is evident that the essence of Tai Chi's "qi," which is essentially force, has distinct characteristics of "momentum transfer":
1. The "qi" in Tai Chi has the property of transmission. Phrases from ancient boxing manuals such as "from foot to leg, from leg to body, practicing as one qi," "its root is in the foot, issuing from the leg, controlled by the waist, manifesting in the fingertips, from foot to leg to waist, must always be an integral one qi," and "moves as if drawing silk, clarity everywhere" clearly reflect this situation. In particular, the manuals often liken the transmission of "qi" to the waving of a silk ribbon, further illustrating that this "qi" is transferred in wave-like forms.
2. The occurrence and transmission of Tai Chi's "qi" require physical relaxation as an essential condition. Terms like "loose and still," "soft but not hard," "extremely soft," "abdomen relaxed with rising qi," and phrases from the Yang Family Old Manual such as "must not lose its softness" and "indeed there is a heart's softness" all reflect this requirement. Especially notable are Mr. Yang Chengfu's statements about "not using force" and "practicing Tai Chi does not involve manual action," which point out the essence of "relaxed and clean" and "soft."
3. The transmission of Tai Chi's "qi" depends on the correct response of sequential "opposite-direction movements" across different parts of the body. Phrases such as "settled," "controlled by the waist," "qi like a wheel, waist like an axle," "having front means having back," "force originates from the spine," "upright and comfortable," and "supporting all sides" all reflect this situation. Therefore, the majority of the "qi" mentioned in the ancient Tai Chi manuals refers to "momentum transfer."
Although the nature of Tai Chi's "qi" as "momentum transfer" is similar to what modern mechanics describes regarding the "momentum transfer" in whips or ropes and what modern badminton research describes as "momentum transfer," there are still specific differences. This is because:
Firstly, Tai Chi's adherence to sticking, connecting, following, and accompanying requires that limbs make others feel "never getting force." For example, when someone pushes or presses an arm trained with "qi," it should feel like pushing or pressing a severed arm floating on water; the force applied to the arm cannot reach the torso through this arm. Therefore, the intensity of this "qi"-based force is very small, as Mr. Zheng Manqing said, not exceeding "four ounces." To enable such a small force to be transmitted from the foot to the hand, both initiating movement and exerting no external force, Tai Chi requires a particularly high level of full-body relaxation. For Tai Chi's "qi," any local effort used by the limbs for movement becomes an obstacle to its transmission, so it is necessary to strive for the limbs to "not use force." Simultaneously, only this kind of "qi" can smoothly transmit from the foot to the hand, ensuring the effective guarantee that the whole body and limbs can "not use force." Such local efforts used by the limbs are referred to in ancient boxing manuals as "pure rigid force." Thus, the manuals say: "With qi there is no power, without qi there is pure rigidity." This is a type of intertextual sentence mainly found from pre-Qin to Ming dynasties. Translated into modern Chinese, it means "With qi there is no pure rigid force, without qi there is pure rigid force." Meaning: If the movement is caused by "qi," there is no "pure rigid force" in the limbs; if there is no "qi" in the limbs, the movement is caused by "pure rigid force." This indicates that "qi" and "pure rigid force" are mutually exclusive; when "pure rigid force" reaches a certain level, "qi" cannot occur or transmit; when "qi" can occur and transmit, "pure rigid force" must be eliminated. In the Yang Family Old Manual, this "pure rigid force" is simply called "force." These are special characteristics of Tai Chi's "qi" in terms of "momentum transfer."
Secondly, Tai Chi emphasizes the use of "qi" to achieve victory with weakness over strength. Therefore, the "opposite-direction movements" necessary for "momentum transfer" are especially reinforced. This kind of "opposite-direction movement" is a bodily reaction not typically associated with general use of "force," thus requiring the formation of special neural responses. In ancient Chinese, these special neural responses could only be represented by "intention." Hence, practicing Tai Chi places great emphasis on training "using intention." For instance, the transmission of "qi" is somewhat similar to the diffusion of water waves, the advancement of tides, or a straight line of billiard balls where hitting the nearest ball causes it to roll forward and strike the second ball, transferring momentum and stopping itself. The second ball then continues forward to strike the third ball, and so on. In this process, the motion directions of the three balls are often opposite to each other, forming "opposite-direction movements." Specifically, when "qi" initiates movement, the tendency of the hands and body is often opposite, as is the tendency between the body and legs. For example, in the initial posture of lifting both hands forward, while the hands move forward, the body contracts the abdomen and sinks the chest backward. Actually, the forward motion of the hands is caused by the backward tendency of the body. In the transition from White Crane Spreads Wings to Brush Knee Twist Step, the right hand moves forward to receive, while the body rotates slightly to the right around the left hip, moving backward. In fact, the forward motion of the right hand is caused by the backward motion of the body. When the hand pulls backward in Brush Knee Twist Step, the body tends forward with contracted abdomen and sunk chest. Actually, the backward pull of the hand is caused by the forward tendency of the body. In the push and press motion of Brush Knee Twist Step, while the hands move forward, the body leans backward with an extended spine and pulled back. Actually, the forward motion of the hands is also caused by the backward tendency of the body. If not done this way, the transmission of "qi" would be obstructed, and the cause of the movement would be "force" rather than "qi." Such opposite reactions also meet the needs of dissolving through sticking, connecting, following, and accompanying. Precisely for this reason, Mr. Yang Chengfu's "Ten Essentials of Tai Chi Chuan" states: "If not using force but using intention, wherever intention goes, qi follows." Here, "and" is a coordinating conjunction equivalent to "and" or "also" in modern Chinese. Many people today misinterpret this "and" as the adversative conjunction "but," taking this statement as a choice between using "force" and using "intention," which is incorrect. The meaning of this statement is not either using "force" or using "intention," but rather not using "force" and using "intention." That is, due to relaxation without using force, with the neural response of "opposite-direction movement" or "using intention," the essence of "momentum transfer" in "qi" can occur and transmit to cause movement. The momentum transfer in whips and badminton exhibits obvious wave-like forms, whereas the transmission of Tai Chi's "qi" in the body does not have an obvious wave-like shape, which is another special characteristic of the "momentum transfer" in Tai Chi's "qi."
Since humans are accustomed to limb activities being caused by sustained muscle tension, causing limb activities with "qi" is unfamiliar and uncomfortable for most people, making it impossible to instantly understand. Even if one understands, it is impossible to immediately gain this skill. This is because most people are not accustomed to full-body relaxation or to this kind of "opposite-direction movement" of "using intention." However, as long as one continuously practices relaxation without using force and the neural response of "opposite-direction