What causes electrical shock on left arm when approaching target heart rate?
Patient: i've recently started using the treadmill at the gym, and i haven't done anything for years.  when i approach my target heart rate (123 and up) i get a feeling of small electrical shocks on the outside of my left arm.  i do not feel any other symptoms.  when i maintain below 120 its fine. Doctor: Sir i think these should is are muscle twitching or fasciculation . You need to confirm it then you please get your proper treadmill test in cardiac lab. Some routine blood investigations to see electrolytes and ECG 12 lead. i am sure if you continue your work out it will gradually went off.Best regards