What do you do when you hit your knee on a chair? You touch your knee and you rub it, don’t you? Some scientists believe that we rub the hurting body part to reduce the pain. They call this “gate control theory of pain”.
This theory is quite complicated. However, to get an idea of it, imagine again the wires called neurons. There are wires that send pain and others that send the rubbing sensation to the brain. These wires reach the brain via the spinal cord. At some point, both wires meet and pass through a place, which you can think of as a gate. This gate has a certain width that decides which signals can go through. If there is only the pain signal, without the rubbing, the gate will let all of the pain through. However, if you also rub your knee, the gate will let the rubbing signal pass but only part of the pain signal. That is why you reduce the pain if you rub your injured body part

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