There are two main reasons for muscle atrophy in the arm: First, due to nerve damage, the nerves cannot innervate the muscles in the arm, and the muscles will gradually atrophy and lose strength, and are often combined with adhesions in the surrounding tissues, resulting in significant local pain and striae. Second, due to injury to the muscle position, common in fractures and surrounding muscles, ligaments, tendons and other soft tissue injuries, the need for external plaster fixation or surgery, bed rest and recuperation, during the recuperation period due to less muscle activity, will also lead to muscle atrophy, but, after the fracture and surrounding tissue healing, with rehabilitation exercises gradually, muscle atrophy will be significantly improved However, after the fracture and the surrounding tissues heal, the muscle atrophy will improve significantly with rehabilitation exercises. In addition, the muscle atrophy may also occur due to low activity because of the obvious pain in the muscle after the injury, which can be very painful when moving.