Abdominal Breathing

腹式呼吸は，息を吸う際に腹が膨らみ，息を吐く際にはその膨らんだ腹が元に戻る。したがって，腹の動きは胸式呼吸と逆になる。ただ，空気が入るのは肺（胸部）なので，実際に腹に空気が入るわけではない。腹圧を上げて横隔膜を下げることで肺の容積が増えるために，外界との気圧差が生じて空気が入る。また，腹式呼吸では，胸式呼吸とは違い，息を吐くことに重点が置かれている。


In abdominal breathing, the abdomen swells in inhaling, while the swelled abdomen returns to be as before in exhaling. Therefore, the abdomen in abdominal breathing moves in a reverse way to the one in costal breathing. But, the air is filled in the lungs (the chest), not exactly in the abdomen. Rising the abdominal muscle pressure and lowering the diaphragm (midriff) makes a capacity of the lungs increased. Then, the air goes in the lungs because the difference in air pressure between inside and outside occurs. Besides, abdominal breathing puts a stress on the process of exhaling, different from costal breathing.