Master Chen has said in an interview that at certain stage he felt his overall strength get much better.
I asked him how was his training different after that stage. His reply is that the training progress to a different dimension. Each dimensions becoming less physical.
However student must complete the first level, in the sense that body is prepared for the next one. An analogy of machine is that the parts must be cleaned, so it can moves together without restriction.
This is what I felt in my training, in certain posture I can do a taiji move, but not in other as the joints at some angle are stuck.
Diagram is my current understanding of stages in taiji training.
