The common causes of shoulder pain include lactic acid accumulation, shoulder soft tissue injury, cervical spondylosis, etc. According to the specific causes, corresponding methods can be taken to relieve, including general treatment, medication, physical therapy, surgery and so on. 1. Lactic acid accumulation: when practicing double bar arm flexion and extension, the muscles in the shoulder area will be exercised, and the accumulation of lactic acid will lead to pain, which can be relieved by local massage and hot compresses, and pay attention to sufficient rest, avoiding strenuous exercise, lifting heavy objects, and so on. 2. Shoulder soft tissue injury: too strenuous flexion and extension movements or incorrect posture can lead to soft tissue injury in the shoulder area, which in turn causes pain, can take non-steroidal anti-inflammatory drugs (such as ibuprofen) for relief. 3. Cervical spondylosis: when suffering from cervical spondylosis, double bar arm flexion and extension may induce pain aggravation, at this time, you can take non-steroidal anti-inflammatory drugs (e.g., ibuprofen), cervical spine traction to relieve the pain, and in serious cases, you need to consider surgical treatment. Double bar arm extension shoulder pain may also be related to other reasons, it is recommended to consult a doctor in time to clarify the cause, and standardized treatment under the guidance of the doctor.