The Principle of Separating Movement from Motion
"One of my instructors used to tell me that the most important principle in learning any martial art is that movement is not the same as motion. "Motions" are what we see (or think we see), and "movements" are the muscular actions that produce the motions. Especially in the beginning, a major problem in learning martial arts is that we try to imitate the instructor's motions with untrained movements. Because an imitated motion doesn't necessarily require the same movements that produce the desired motion, the techniques are often weak. The purpose of training is to learn to make the movements that produce the motions. Of course, these movements are not obvious and are often not called out specifically during training.
"Analyzing Movement in the Body Arts: Lessons from Hanbojutsu"