Strengthen the Body Against Attacks
The daken taijutsu of Ninjutsu involves two different methods that are said to have been developed in China. Koppō jutsu involves bone-crushing techniques against the opponent’s harder bones and koshi jutsu involves stabbing against muscles and organs. In order to make the body weapons more resistant to blows, there are numerous ways to harden them. This is absolutely necessary, as an untrained body weapon easily gets painful swelling or bruising.
Fingers and Hands
The fingers or hands are strengthened by doing the same thing as a cat. The Ninja slams his hands or fingers against a tree, gradually strengthening them. A cushion filled with lead shots or stones is also suitable. Or you hit the pillow and grab it powerfully.
The best way to harden the spear hand is to poke it in a bucket filled with sand, lead shot, or pebbles. You start with soft sand and as you progress harder sand, small stones and larger stones follow.
Arms and Shins
The best way to strengthen arms and shins is to bang them against a tree. Training makes you immune to enemy strikes on those sensitive spots. The muscles of the abdomen, solar plexus, neck, and other sensitive areas should be better protected through muscle training.
Hardening is Uncomfortable
Hardening should be uncomfortable but not painful and allow enough relaxation between workouts. Only a slow increase in hardening leads to success.
The other body weapons are also strengthened on trees or pillows. With enough stamina, the body weapons become effective tools. Grandmaster Takamatsu was able to rip entire pieces of bark from a tree with his fingers. Through years of training, his fingernails became as sharp and hard as daggers.