The back is where the tendons are located, and the bladder meridian of the foot sun on both sides of the spine is closely related to the internal organs. The five internal organs of the human body, such as liver, heart, pericardium, spleen, lung, kidney, large intestine, small intestine, triple energizer, gallbladder, stomach, bladder and the twelve meridians, are all concentrated in the back. Often hitting the back with half-empty fists or mallet can stimulate and enhance the qi of the back meridians, promote the circulation of qi and blood, balance yin and yang, dredge the meridians and invigorate the viscera, thus enhancing the immune function of the body and delaying aging.