Sudden soreness in the arm may be caused by heavy physical labor, trauma, and chronic injury to soft tissues, fascia, and periosteum, etc., as follows: First, over-exercise: the previous day did a long period of heavy physical labor or strenuous exercise, which led to the accumulation of lactic acid in the muscles of the arm, thus stimulating the muscles to cause soreness, pain, and weakness, generally this situation can be rested for a few days, and after the metabolism of lactic acid is completed, the The soreness can be relieved naturally. Second, trauma: the arm may have been traumatized, usually this will appear local swelling or petechiae formation. Third, chronic injury to the soft tissue, fascia and periosteum: chronic injury to the soft tissue, fascia and periosteum of the arm, resulting in localized sterile inflammation over time, leading to soreness and pain, usually in people who often do upper limb sports, heavy physical labor or strenuous exercise.