Hard Qi Gong, or  Chi Kung is a type of Wai Dan, or external elixir, training. The distinction between hard and soft qi gong is in many ways similar to the distinction between hard and soft martial arts; in both cases the so called hard style is more external, focussing on external strength and power, whereas the soft style focusses more on the flow of energy within the body. Hard qi gong focusses on the strengthening of the muscles and tendons, leading 'guardian chi', or wei chi, to the skin to protect the body (as in Iron Skills training / Shaolin Steel Jacket), and other external manifestations of chi. Although many forms of hard qi gong have beneficial effects for the health this style is used predominately in martial arts applications, whereas soft chi kung is often used exclusively for health purposes.