Please take a moment and view this Youtube video which was shot at a seminar that Master Hwa did for World Tai Chi Day in Rochester, NY: Internal Discipline in Walking and Kicking
Question: “I truly don't understand this. How can this lead to a quick kicking thrust that can be executed reflexively?”
I studied other styles as well as Wu’s Style for a long time before beginning Classical Tai Chi. Certainly in this as well as other styles the “ mind-body relation starts from intense struggle and engagement in the beginner’s stage” as my teacher says. Then the learning “proceeds to total disengagement”. The mind can enjoy things in the practice almost as if the practice is being done by someone else, not a “cruise control” but more like independent observation. For martial purposes a kick can be done quickly and reflexively because the movement has become subconscious.
As to the mechanics of the movement and how it is done:
The psoas will become engaged, as will the gluteal and femoral muscles but the origin of the movement should come from the transversus abdominis and rectus.. the long abdominal muscles...at first you must exaggerate the contraction of the lateral and oblique muscles of the abdomen and squeeze the gluteals,relax the leg and the foot... A low kick is a quick sudden, unexpected (for its martial art application) thrust from the abdomen and back through the pelvis and the leg. That means that from the side the leg is kicking, the pelvis thrusts downward from the tilt which transmits power through the leg.
Question: “I have never been told to do that, and matter of fact, the instruction for the small frame is in direct opposition to what you're advocating, a release of the abdominals, using breath so as to allow the load bearing to penetrate through the musculature and rest inside the qua.”
First of all, this is not weightlifting, and so the breath should be natural. You have to take into account the framework from which you say you are executing your kick as. You say “small frame”, when in actuality there is considerable difference in the size between Wu Style Small Frame and Classical Tai Chi Compact frame. I did the Wu Style Small frame for many years and to do what you say (which is true for that frame)I was taught to primarily use the contracted muscles of the leg to lift and walk or kick. In other words, the leg had to move like a “telescope” with the individual segments, calf/thigh, etc. contracting and extending or even swinging from the hip as Master Hwa shows. Not much different from everyday walking and kicking is using the same muscles.
With the individual segments of the leg contracting and expanding, the energy does not flow uninterrupted. In fact the flow of energy is interrupted at the joints themselves. What Master Hwa shows is the leg completely relaxed, no bending at the joints and when the power is delivered from the abdominal and back, it goes straight through…no interruption. Of course, and unlike the small frame you speak of, the kicks in Classical Tai Chi go no higher than the opponents knee. If you want it to go higher then you pull the opponent down toward the rising foot using “yank” (Tsai). This goes to the heart of the old Tai Chi saying: “Do not kick unless you can kick with 3 legs”. This means, your one leg supports you while you are in contact with the opponent who is standing on his 2 legs.