In the conversation of Mr. Bob Sapp abt. the leg joint bending excercise, it might be similar to what Master Jan Kallenbach was doing, which is called Ritsuzen &/or what they called it Tanto in Yiquan of the Chinese martial art. I think it is nothing to do with mystic Zen of China or their special martial arts if you understand Rituzen from physical point of view. Lots of former &/or present Karate, Judo, any martial artists people shifted to this and returned back and forth from more than 70 yrs ago including Master Jan Kallenbach. Kung Fu people just want those excercise as their special & mystic technique IMO.