I did some digging, and found some more material on the fist trajectory in Deflect, Parry, and Punch as Fu Zhongwen describes it. Gu Liuxin’s 1982 magnum opus, _Taijiquan Shu_ (The Art of Taijiquan), has exhaustively minute form instuctions of the Yang form. He not only addresses the alignment of the fist with the centerline, but he also uses the phrase “quan cong xin fa” (fist that issues from the heart) that Fu used in his Important Points on the sequence. The description I’ve translated here picks up after the left palm’s “parry” has already issued, and the right fist is at the lower right flank:
“The waist turns slightly left. The left hand, sinking the elbow, draws in slightly, its elbow tip about the distance of one horizontal plus one vertical fist from the ribs. The right fist extends forward and upward toward the centerline (zhongxian), it’s thumb about the distance of one horizontal plus one vertical fist from the chest hollow (xiong wo), the heart of the fist obliqely facing the upper left. The eyes look levelly forward. . . .”
“The waist and torso continue turning left, [until] the torso faces squarely forward, the center of gravity gradually shifting to the left leg [until] the left foot is entirely planted full (ta shi). Bend the left leg, tread (deng) the right leg, forming a left bow stance. The right fist turns in, [causing the] tiger’s mouth to face upward, and strikes out from the centerline in front of the hollow of the chest (xiong wo). Sink the elbow—the elbow joint is slightly bent and not straight. The left palm collects slightly in, [while] sinking the elbow and seating the wrist, [maintaining] a standing palm. The heart of the palm faces right—its edge toward the front, the finger tips obliquely forward and up—placed beside the inner edge of the right forearm at the bend of the elbow. The eyes look levelly forward, with the gaze attending to the right fist striking forth. Lower (luo) the kua and settle (ta) the waist; the sacrum area is firm and filled out, the jin sinks down through the crotch (dang jin xia chen). The jin comes up from the heel of the foot, threading joint by joint to reach the fist (jie jie guan chuan zhi quan). . . .”
Then in his explanation section following the form instructions, Gu gets even more explicit regarding the trajectory, and adds some wonderful detail regarding the frame:
“In this form, both the right hand’s deflect (ban), and the left hand’s parry (lan) are combined attack and defense movements of close distance hand-to-hand boxing methods. When deflect and parry are deployed, they cannot be too distant from the body. You also must not raise the elbows; from beginning to end you must attend to sinking the elbows [to] attain ‘zhou bu li lei’ (elbows don’t leave the ribs). If you’re able to sink the elbows, you will not only tighten up your defense, you will also enable a great increase of strength (jinli). Issuing the fist’s strike from your own chest hollow’s center line (xiong wo zhongxian), [and] expressing the strike toward the opponent’s chest hollow—this is called ‘fist issues from heart’ (quan cong xin fa).”
Gu Liuxin was of course something of an acquisitions editor/developmental editor of Fu Zhongwen’s book, as well as the books of other leading taijiquan masters, in the late fifties and early sixties. The fact that his and Fu’s descriptions both refer to this alignment of the fist with the centerline, and both use the phrase “fist that issues from the heart,” suggests that 1) Fu got this from Gu; 2) Gu got it from Fu; or, 3) both got it from a common source.
Audi, does this clarify the concept of the fist’s trajectory? Again, I realize this seems to be slightly different from the trajectory taught by Yang Zhenduo. I initially learned the same described centerline trajectory from my first sifu, and have experimented with both orientations. Do you have any thoughts about the structural merits of the alignment as described?