Practice in Kamakura centered on learning through taking a great deal of ukemi, and it was perhaps there that I began to realize the reality of hara for the first time. In later years, I learned that repetition isn’t always necessary in order to strengthen ki power.
Takeda Sensei would throw each of his students after class until they could no longer rise to their feet. I remember the feeling quite well. Regardless of how much stamina you build up, there comes a point where the physical muscles of your legs will no longer lift you up, support you, or move at all. I became able to take ukemi almost inexhaustibly, but there were times when I fell and simply couldn’t get up.