By physically oscillating in a specific direction, the principle of chest physical therapy promotes directional body position drainage. It generates periodic therapeutic forces on the human body surface. This directional therapeutic force has strong penetrating effect and can penetrate the skin layer, muscles, tissues and body fluids. The vertical component force it produces through tapping and oscillation can facilitate the relaxation and liquefaction of mucus on the respiratory tract mucosa. It helps patients after surgery and those with weak constitutions enhance their ability to expel mucus and improve the blood circulation in congested lungs.