Frequent muscle throbbing in the upper arm of the left hand may be caused by overwork, cervical spondylosis, hypocalcemia and other reasons. 1. Overwork: it may be caused by long-term weight bearing and frequent exercise of the left upper arm, which may cause muscle spasm and frequent beating due to excessive muscle compression. 2. Cervical spondylosis: mainly caused by cervical degenerative disc changes, chronic injuries, etc. When the patient has neurogenic cervical spondylosis, it can stimulate the nerves, which can cause muscle spasms and throbbing of the left upper arm. 3. Hypocalcemia: it may be caused by vitamin D metabolism disorder, hypoparathyroidism, insufficient intake and so on. Low calcium leads to increased nerve excitability, which can make the left arm muscles jump frequently. Frequent beating of the muscles of the left upper arm may also be caused by other reasons, it is recommended to go to the hospital in a timely manner, follow the doctor’s instructions for treatment, to avoid delaying the condition.