The lack of strength in the arms may be related to overwork, cervical spondylosis, intracranial lesions and so on. 1. Overwork: when the arm after a lot of exercise, due to muscle and other soft tissues are overworked, can lead to short-term weakness of the arm, generally can be relieved after resting for a period of time. 2. Cervical spondylosis: when cervical disc herniation compresses the peripheral nerve roots, it can lead to weakness of the arms due to nerve compression, which can be accompanied by swelling and numbness of the arms. 3. Intracranial lesions: when there is ischemia, hemorrhage or space-occupying lesions in the cranium, due to the damage to the functional areas of the management of the upper limbs, it can cause the arm to be weak, in addition to headache, dizziness, etc., and in severe cases, paralysis can occur. There may be other reasons for the lack of strength in the arms, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.