Came across this video yesterday on Facebook. This type of training has been controversial for many years. Some people think that conditioning parts of the body until you can’t really feel anything is detrimental to the flow of chi.
It can also have severe repercussions during old age.
There’s no denying though that the power it creates is brutal. It really is the definition of turning the body into a weapon.
Here’s Shinjo Sensei of Uechi Ryu Karate: