Thanks for the comments Audi
I think we're all the same...most of us in the Martial Arts world i.e., "we love to keep learning". If you have any references on your patterns, mabe videos or articles i'd love to check them out. Much appreciated.
About what you said:
one thing I might do differently than in the split drill you showed is that I would tend to show split with the arm controlling the opponent's elbow with my palm open and facing away from me rather than in a fist with the back of the fist facing away. In doing split, we would also tend to try to keep the opponent's forearm so that his/her palm and the inside of his/her elbow would be on the same side. If we twist the opponent's arm, I think this would be more to get the opponent's elbow to rise and to apply Roll Back energy to it.
I'd like to explain why I do it that way: In our school there are 3 main ways to split the elbow; up, down & horizontally. Also it is critical before I go further to say that splitting the elbow works best when you attack the triceps tendon point above the actual elbow.
In the drill we are not using the UP...so the focus should be on the down and lateral versions.
Usually if you're going to split on the elbow..it's preceded with some sort of "cai" or pluck (to grab the wrist). Upon doing so, twisting the the wrist so that the thumb side turns down also causes the elbow the point up. This is done on purpose because it binds the opponent. When elbow is pointing up and you extend the arm to make his energy "LONG"...it facilitates the downward split.
As to why I use the backfist side of my arm and NOT the palm side...PENG. The forearm bones consist of the Radius and Ulna, when you use the back side like I did...you also twist the bones and peng provides energy from the Longer reach of your arm. So peng is not just from the Bow (roundness) of your arm and hollow (sink) of your chest, but also it exists in the spiral of your bones. Circles within circles.
**In our school the more you express your jing via connection out towards your fingers....the more advanced you are. Energy from the dan tien doesn't stop at the shoulder or elbow or wrist (unless you want it to), but all the way out to your fingers.
If you use your palm side, you also are doing what I said about twisting true, BUT you are not using the knife of the arm. The problem with this is that you present your muscle / meaty side of your under forearm on the joint. It is too soft for real fighting purposes. The ulna bone is like the knife or axe in splitting the elbow joint and is much more painful and effective. Keep in mind,
the twisting of the thumb down in my example, that is only when a person lets you. As you say, it can be done with the arm all in NON twisted alignment.
For example, I try to twist the wrist but my opponent feels me doing this and he gives some resistance. That answer is easy and simple...taiji follows and I so would I also. Meaning I would follow his resistance and move right into my next thought. That is is just good Taiji in a nutshell...to follow whatever changes the opponent makes. I could do a whole video series just on that but I'm not sure I want to give it all away for free. Haha.