Tai Ji Chuan's basic requirement for upper limb movements is to sink shoulders and elbows. To do this, its essence lies in the flabby abduction of the scapula, that is to say, as long as the scapula sinks and abducts, it will naturally sink its shoulders and elbows. The basic movements of scapula are lifting, sinking, adduction and abduction. The so-called force to the back actually means that when the muscles of the waist and legs exert force, the force propagates along the spine, reaches the scapula, and is transmitted to the arms and hands through the support and conduction of the scapula (the scapula is in a sinking and abduction state). The arm is required to arrive before the force is exerted. The so-called "micro-knot" is the root knot reminder.
"Loose your shoulders", but don't ask or think too much about the "shoulders". Remember the main point of "loose" and stand up first. Loose shoulders involve too many elements, and the more you don't understand, the more confused you become. In fact, the muscles consumed are boring and the tendons are stretched out. As soon as you stretch your muscles, you will understand without others saying. If you can put your shoulders down, your hands will sink, which is a standard. Use the heavy strength of your hands to further relax your shoulders and slowly stretch the tendons in your neck and back. Only in this way can strength sink along the spine, and then waist training can be talked about.