"The use of the lower body itself is not a mistake. However, the way in which you use it, the balance of stillness and motion there, the problem of the internal aspects, and the consciousness… Originally my movement was much faster. Rather then saying muscle, it was the speed of physical force (魄力). O-Sensei often told me “it’s not the body (魄), it’s the mind (魂)”. But I was stupid and I didn’t listen. (laughing)" - more from Hiroshi Kato Sensei on the Aikido Sangenkai blog.