The common causes of left upper arm muscle throbbing are as follows: 1. hypocalcemia or osteoporosis: both can cause increased neuromuscular excitability, and the patient can have left upper arm muscle throbbing symptoms, and in severe cases, spasticity and tension can also cause pain. 2. left upper limb trauma: such as muscle strains or fractures, muscle excitability can also be significantly increased during the recovery period, and local throbbing can easily occur, accompanied by swelling and pain. The symptoms of throbbing in the left upper arm muscles should be highly valued and promptly treated to determine the primary cause, which can lead to complete improvement of the patient’s clinical symptoms. If allowed to develop, the clinical symptoms will continue to worsen and the primary disease will lead to adverse consequences.