In the Japanese arts the term Tanren is used. It means to forge the way that a sword blade is forged, through hard work, and sweat, and hours of training. Under the heat and pressure the hard and soft elements in the body, the mind, and the movements are melded together in the same way that a good sword gains its strength out of a combination of both hard and soft steel.
Many of the kung fu movies include some form of training that is not of the ordinary, but which, to a certain extent, make some sense. Whether some of them are truly valid or not is up to the practitioner.
NOTE: While most of the training aids are fairly self-explanatory, any use of them should only be done after being properly shown the techniques by an instructor. High impact devices should be avoided by those that still have active growth plates. Pain is NOT a good thing and should not be a result of properly using any of these training aids. Improper use may result in serious injury.
The term Tanren is also used to refer to the practice of the instructor moving among the students and validating stances and blocks by testing their alignment than angles through strikes on the student. Common kata for this to be done with include the Naihanchi and Sanchin katas,
Makiwara,
Very common in the world of Okinawan karate and its descendants. This is a wooden post that stands about 5 foot high. It has an appropriate amount of 'spring' to it, so that it isn't an immovable object, but flexes when punched. The padding can be anything from canvass, leather or even rope. While the makiwara does help build bone density and calluses the knuckles, the primary purpose of the tool is to insure a strong and correct punch. The lining up of the knuckles, the wrist and the arm are all necessary to move the makiwara without harm. With appropriate pads added, the makiwara can be used for elbow strikes and even kicks.
