Iron Palm practices aim to increase the bone density this not only makes the hands less vulnerable to damage but also heavier and more capable of damaging (think of being hit with a piece of metal rather then a similarly sized piece of wood). Alongside this the methods develop the tissue and muscles of the hand making them stronger and ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.