One of the very dangerous parts of doing Qi Gong incorrectly is the breathing, if you attempt zen/buddist breathing methods or taoist beathing methods and do these wrong, while doing the energy forms, it can seriously mess up your innards, giving you major gastrointestinal problems, and Ive actually even heard of hemmoroid outbreak s(though i cant verify this, as its never happened to me) and many other things can happen, especially if you attempt high level stuff when just beginning.