Training for Fajin

Video link: Classical Tai Chi walking exercise and Internal Discipline in Tai Chi Walk

A civil conversation about training for Fajin I had with Louis Swaim, a former editor at North Atlantic Books and author of The Essence and Applications of Taijiquan:

Louis: "I think I understand what you are proposing; however, I still find the emphasis surprising. I should say that although we talk about the legs generating Jin, it is true that the waist, arms, and hands also do something. They cannot be limp and may even provide a substantial amount of energy. One of the ways in which I teach as I try to translate my understanding of the classics in everyday terms is to say that we should always generate power with the biggest and strongest muscles available and let smaller muscled do supporting work. According to at least some definitions, the muscles controlling the thighs and pelvis are the strongest. They certainly have more range of motion than the muscles controlling the lumbar spine. I would say that the waist can add power to the legs, but not the other way around. I would say that the legs are the heavy springs and the waist has the medium springs. Once the heavy springs have stored the maximum energy they can, they can share some with the medium springs without loss of collective power; however, if you try to maximize the storage in the medium springs before the heavy ones, you will steal energy from them and limit them."

Jim R: "The compact and tight compact Forms use “pulling” with both front and back. The step size is quite small in a compact Form very small in tight compact…much smaller than even what Wu Gong Yi showed in the Gold Book. That pulling is accomplished by the “engagement” of contracting (abdominal, back, buttock) core muscles with the legs. The style does not eschew pushing with the legs, it uses it with discretion. For instance, it can use pushing once the opponent’s balance is offset, then a pushing movement, even with a larger step, can be added opportunely.

As far as elaborating on the reasoning for “rooted in the feet, generated by the waist, controlled by the legs and manifested through the fingers” as you have talked about in the Classics.iThis statement may be applicable to certain Large Frame moves which use the leg to generate the pushing force. But, it is not applicable in the Compact Form which generates power from the torso, and is important to remember not only the difference in a frame size that I speak of here. It is important to remember how equal and opposite force will be sent from the waist down through the pelvis to the leg, finally absorbed by the ground through the foot. During that instant, the buttock and leg will naturally energize to transmit the force to the feet, thus firming the lower body structure to support the fa jin."