The back is where the tendons are located, and the light meridian of the foot sun on both sides of the spine is closely related to the five internal organs. The five internal organs of 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. Frequently beating the back with half-empty fists or Xiao Mu hammer can stimulate and enhance the qi of the back meridians, promote the circulation of qi and blood, balance yin and yang, dredge meridians and tonify viscera, thus enhancing the immune function of the body and delaying aging.