The causes of hand muscle weakness are as follows: 1, hand muscle weakness may be caused by overworked arms, in daily life hands lifting heavy objects for too long, or long uninterrupted writing will cause excessive fatigue of arm muscles, resulting in the involvement of acetylcholine receptors on the neuromuscular junction, resulting in symptoms of hand muscle weakness. The hand muscle weakness may also be caused by cervical spondylosis, due to cervical spine joint protrusion or degenerative disease, which can cause compression and involvement of peripheral nerves and blood vessels, resulting in unilateral arm or hands blood circulation obstruction, abnormal nerve sensation, resulting in muscle spasm around the blood vessels and nerves hand muscle weakness, finger numbness, etc. 3, arm Muscle weakness can also be considered a muscle lesion, such as polymyositis, which can cause muscle weakness in the arm while causing symptoms of muscle pain and muscle atrophy.