Re: Tenkan - advanced
Just a note before I start. I'm not writing about tenkan in modern aikido. What I write will most likely make no sense at all to most people training in modern aikido.
If you look at the way of aiki (unless noted, by aiki, I mean the Daito ryu aiki which Ueshiba Morihei exemplified) as a method to building a martial and mental body, then the focus is primarily on the person rather than the attacker/uke.
If we look at tenkan in a manner which fits with aiki, then we first look within at what is changing with turning.
There were some good posts on the other thread. I should have included something about the hara/center moving, but didn't. I'll paste my list here and add to it.
1. Imagine stretching the spine upwards and downwards and that it's a straight line. The spine is important and should be kept straight, for the most part. When you turn, if the spine kinks in any manner or deviates from straight up-down, then you will lose structure, stability, and power. (For the most part.)
2. Once you have that, the center starts turning the entire upper body region (from both shoulders all the way down to the "V" area between the hips) around the spine. Imagine the spine turning (clockwise or counterclockwise) in place as you do this. The center is the connection point through the hips to the legs. The center is the connection point through the upper body to the arms.
3. Then at a point where the center and upper body turn starts pulling the legs through the hips, complete the turn. Don't move the hips before 1 and 2 are initiated.
1. The spine is capable of handling strong loads. See the research articles about African men and women who carry loads on top of their heads efficiently and with a lot less energy.
2. The shoulder and hip joints are two if the major areas of weakness. Slack or a disconnect in these joints will cause loss of stability, structure, and power. Connection from hands to center and feet to center through those joints is a must. Just turning from the rib cage to the shoulders will not work. This is a disconnect from the center and "whole body".
3. If hips and center are joined and move together, or if hips move first, then there is a body issue where same side weighted can be a disadvantage. Same side weighting is the idea of getting someone to put weight all on one side. Judo people tend to do this to the other person right before a throw.
Overall, in many videos of Ueshiba, Shioda, etc, you can slow the video down and watch the movements between their shoulders and their hips. Most of the time, you will see the shoulders start to turn (one going forward while the opposite goes backwards) before they move their hips. In some instances, you can see that their shoulders have turned and then they move straight forward. IMO, an indication that their center initiated movement around the spine starts first and then their hips move. Unfortunately, their body is highly developed and the movements are small and hard to see many times.
I haven't included intent, spirals, or breathe in this post. They are too involved to actually write about, but they are definitely still part of everything. And I didn't mention "cross line" body because I wanted to focus on hips, center, and shoulders.