Reverse breathing
Reverse breathing is a breathing technique associated with yoga and qigong. It consists of expanding the abdomen while breathing out through the nose, and then compressing it while inhaling via the mouth -- the opposite of what an abdomen would do during natural, instinctive breathing. Via this process there can be paid especially close attention to the act of breathing. A pure, inner type of thought focus may thus arise.
The technique is also widely practised in a number of martial arts notably Chinese systems such as Baguazhang, T'ai chi ch'uan, and other styles of Kung Fu. The reverse breathing is believed to activate healing and protective Chi as the practitioner is consciously controlling the breath in a way opposite to normal breathing. By expanding the abdomen while delivering some technique (e.g. punch), the martial artists also protects the inner organs from any received counterattack.