Cady Goldfield

There are Japanese systems that "make people pop up off the floor and fly several feet backward" too. It's just not mainstream -- you don't see dojo on every block with that curriculum because the arts tend to be old bujutsu.

It is quite likely that these methods were obtained by Japanese people from Chinese sources a long time ago. It's too sophisticated to just pop up spontaneously, and the Chinese have a long history of such things. The Japanese practitioners since have adapted the methods to suit their particular environments, but the fundamentals don't change.