The causes of muscle pain as soon as the arm is exerted include myofasciitis, cervical spondylosis, and muscle fiber injury. 1. Myofasciitis: the aseptic inflammatory reaction of muscle and fascia, due to the lack of thorough treatment in the acute stage and turn into chronic; or due to repeated strain, wind and cold and other adverse stimuli, can be repeated persistent or intermittent chronic muscle pain, soreness and weakness and other symptoms. 2. Cervical spondylosis: due to the compression of nerves caused by cervical spondylosis, resulting in abnormal nerve conduction of muscles, which leads to the symptoms of pain in the upper arm. 3. muscle fiber injury: such as excessive use of the upper limbs lead to more than the upper limbs to withstand the load, thus causing the upper limb muscles and muscle fibers are strained, resulting in the formation of local bruising and inflammatory edema foci, and then when you exert yourself, the damage to the muscle fibers will be stimulated by pulling, the symptoms of pain. The arm muscle pain may also have other causes, such as occupational lesions, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.