Hello, Brief answer: You need to change Metoprolol dosage or switch back to Propranolol if needed, your right arm developed a cramp, not related to heart. Explanation: My opinion is that palpitations have many causes, anxiety, excess caffeinated drinks, thyroid problem, pregnancy and anemia are most common causes. In your case, you should take a rhythm controlling drug that fits your condition, if selective beta blockers like Metoprolol are more convenient than propranolol then you should adhere to it. May change the dose or select other type of beta blocker would control your palpitations. Your arm condition has nothing to do with your heart, if you used your right arm vigorously during golfing may be that is just a muscle cramp. Nothing serious here. The information provided by you is not sufficient to provide a good opinion. If someone comes to me with this condition I would ask them about the diagnosis or cause of palpitations, also the dosage of beta blocker to alter it accordingly. Conclusion: I suggest you good hydration in sports activity, check with your physician about drug modification. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Mahmmad Gamal