Target heart rate on a beta blocker

Ask the doctor

Q. Your article about interval training in the September issue suggests a target heart rate of at least 80% of your maximum heart rate during the high-intensity intervals. But what about people like me who take drugs such as metoprolol, which lowers the heart rate? Should I adjust my target heart rate for exercise?

A. Metoprolol (Lopressor, Toprol) belongs to a class of drugs known as beta blockers. As you mentioned, these drugs reduce your heart rate; they also lower blood pressure. They work by blocking the effects of the hormone epinephrine (also known as adrenaline), causing your heart to beat more slowly and with less force. These drugs are often prescribed for people who have had a heart attack, as well as those with heart failure, atrial fibrillation, or angina.