There are many reasons for shoulder weakness, such as overexertion, cervical spondylosis and frozen shoulder. 1. Overwork: Prolonged use of the shoulder joint for weight-bearing, maintaining a posture for a long time, etc., may lead to excessive strain on the shoulder muscles and congestion in the muscles, thus leading to the phenomenon of heavy shoulders with a sense of pressure and fatigue. 2. Cervical spondylosis: acute attack of cervical spondylosis can lead to edema of the nerve root, which can cause the phenomenon of heavy shoulders with a sense of pressure and fatigue, accompanied by numbness and pain in the hands, pain in the neck, and restriction of activities. 3. Frozen shoulder: heavy shoulders with a sense of pressure and fatigue may also be due to frozen shoulder, frozen shoulder is a common shoulder joint disease, the early onset will cause a sense of pressure, a sense of heaviness, and at the same time, there are limited activities, the phenomenon of pain. There are many reasons for heavy shoulders and fatigue, and after the symptoms appear, it is recommended to go to the hospital in time to improve the examination, and take standardized treatment according to the doctor’s instructions.