Soreness and weakness of the arms may be caused by over-activity, or it may be due to diseases such as fasciitis and cervical spondylosis. 1. Over-activity: If the arm has been engaged in heavy physical activities for a long time recently, resulting in arm muscle fatigue and lactic acid accumulation, it is easy to produce symptoms such as soreness and weakness, which is a normal phenomenon. 2. Fasciitis: the etiology of this disease is not clear, research has shown that it may be associated with long-term incorrect posture caused by excessive strain, or cold, exertion and other factors, mainly manifested as pain in the affected area, weakness and so on. 3. Cervical spondylosis: the basic causes of this disease include cervical degeneration, chronic strain injury, spinal stenosis, etc., which can be induced by cold, sudden impact and other factors, and some patients will experience symptoms such as numbness and pain in the upper limbs, and in severe cases, the upper limbs will be heavy and weak, so the pain and weakness of the arms may be caused by cervical spondylosis. 4. Other: clinically, we can also consider the arm pain and weakness caused by frozen shoulder, brachial plexus neuritis and other diseases. If arm pain and weakness is excluded from the normal situation, the patient needs to go to the hospital in time, to clarify the specific causes, and follow the doctor’s instructions for treatment.