I'll not be held responsible for any injuries or suffering if anyone tries this techniques. It requires special guidance froma qualified instructor. I doubt you will find many instructors that know this technique as they are very old techniques and are only usually taught to special students with high potential, dedicated, respect teacher and self-respect, and patience.
On a daily basis, stand in horse riding stance. If you get tired take a rest then try again. When you can stand in horse riding stance for 2 hours you have achieved the first stage of this art. You must now start to run long distances; this will make your legs very strong and tough: It says in the old texts that your legs will be invincible. For the next stage bury wood stakes (at least 6 inches in diameter) in the ground and continually kick them with your feet and legs. At first your legs will hurt a lot and will become bruised, but within a few weeks your legs and muscles will become tough and you will not feel the pain. Once you can shake or even break the stake, bury bigger stakes into the ground and resume practice. It says that after three years of training, your kicks can shake the branches of big trees or brake the trunk for a small tree.