Biceps weakness may be caused by the following reasons: 1. Disuse muscle atrophy may occur here, often seen in patients due to upper limb trauma requiring prolonged immobilization or braking, or due to the patient’s need to work sitting or standing for long periods of time, which leads to muscle atrophy here, often manifesting as biceps weakness, and accompanied by a significant decrease in muscle volume here. 2. It may be caused by cervical spine related diseases, such as cervical medullary related injuries or cervical spinal canal related occupations, which may lead to compression and stimulation of the nerve centers innervating the biceps, leading to a significant decrease in muscle strength and even paralysis. 3. It may be caused by overexertion, such as excessive lifting and carrying of heavy objects by the patient before, leading to overexertion of the muscles here. 4. It may be caused by autoimmune related diseases, such as Grin-Barre syndrome or progressive myasthenia gravis, which may result in muscle weakness.