The Iron Body techniques of Shaolin Kung Fu are meant to harden the body through strict, repetitive training. But is there any science behind it? If done incorrectly, Iron Hand (more popularly known as Iron Fist in the West) can leave the student disfigured. However, with proper training and care, the skin, muscles, and bones can harden giving the practitioner fists of steel. This is because Iron Hand actually breaks the bones of the hand and they heal with greater strength.
The breaks are not large, they are called microfractures. If they are allowed to heal properly, the body will deposit a dense honeycomb structure to strengthen the bones.
When microfractures occur, bone is remodeled by cells called osteoclasts and osteoblasts. The osteoclasts remove bone, and then the osteoblasts come in and deposit the building blocks for a stronger bone. When the bone has been damaged, the osteoblasts deposit a dense, honeycomb structure which will be stronger than before.
However, if the bone is not given an opportunity to heal, the osteoblasts cannot heal the bone fast enough and the microfractures will be a point of weakness. This delicate balance is the key to Iron Hand.