When the arm is stretched out, the tendons feel painful, there are two main reasons for this situation: First, the arm position of the muscles, tendons, ligaments and other soft tissue strains or strains, will form a sterile local inflammatory lesion, gradually appear inflammatory edema, in the arm stretched out due to the location of the lesion is stretched, stimulation, will lead to pain is more obvious. In a relaxed state, there is no pain because it is not stretched. Second, because the arm location of the muscles, tendons, ligaments and other soft tissue adhesions, such as after injury or often cold, fatigue, will lead to the formation of local inflammation, inflammatory metabolites in the process of absorption will easily lead to adhesions of the surrounding soft tissues, in the stretching activities due to the adhesions of the tissues are stretched, there will also be obvious pain.