Reverse breathing

Reverse breathing (also reverse abdominal breathing or Taoist breathing) is a breathing technique associated with qigong and martial arts. It consists of compressing the abdomen while inhaling through the mouth, and expanding it while exhaling through the nose. Practitioners believe that consciously controlling this movement in a way opposite to normal breathing can build up qi for various applications.

Uses
The technique is practiced in martial arts including baguazhang, tai chi and other styles of kung fu. Expanding the abdomen while delivering a technique (e.g. punch) can also protect the inner organs from a received counterattack.