Takashi-san made us physically do tenkan and kaiten with straight legs, then from kibadachi, then from between those extremes. The point was made that the lower we sink, the more we are forced to use the balls of our feet and the quicker we can pivot and turn. This was a nice demonstration. I know from experience that showing and explaining to pivot on the balls of the feet seldom does any good, but putting students in a position where they are forced to experience it is helpful.