Abdominal breathing. Common breathing methods are divided into chest breathing and abdominal breathing. Among them, abdominal breathing is divided into anterior abdominal breathing and posterior abdominal breathing. The so-called "breathing along the abdomen" means that the abdomen naturally bulges when inhaling and naturally adducts when exhaling. Abdominal breathing is physiologically called isovolumic breathing. When inhaling, the abdominal muscles relax, the diaphragm descends and the abdominal wall gradually bulges. When exhaling, the abdominal muscles contract, the abdominal wall retracts or slightly invaginates, and the diaphragm rises and recovers. The so-called "reverse abdominal breathing" refers to the natural adduction of the abdomen when inhaling; When exhaling, the lower abdomen naturally bulges. Reverse abdominal breathing is physiologically called variable volume breathing. When inhaling, the abdominal muscles contract, the abdominal wall retracts or slightly invaginates, and the diaphragm contracts and shrinks, making the abdominal cavity smaller; When exhaling, the abdominal muscles relax, the abdominal wall bulges and the diaphragm rises and falls, which makes the abdominal cavity larger. Reverse abdominal breathing has a great influence on internal organs, which is similar to massaging internal organs and helps to improve gastrointestinal function.