Beta blockers slow the heart rate. Taking a beta blocker can keep your heart rate from going up the way it usually does when you exercise. So you might not be able to reach your target heart rate. Your target heart rate is the number of heartbeats a minute that you aim for to make sure you're working hard enough.

When taking a beta blocker, you might never reach your target heart rate no matter how hard you exercise. But that doesn't mean that exercise isn't helping your heart.

There's no way to know the exact effect of beta blockers on your heart rate. An exercise stress test can measure how hard the heart pumps. This test checks blood flow through the heart while you ride an exercise bike or walk on a treadmill. Your health care professional may suggest this test to find your target heart rate.

Another way to measure how hard you exercise is using what's called a perceived exertion scale. The Borg Rating of Perceived Exertion Scale is one such tool. With this method, you judge how hard you think you're exercising based on how much effort it's taking, how hard you're breathing and how tired you get. Ask a member of your care team to help you find and use an exertion scale.

Most workouts should feel somewhat hard. That means they take work, but you can keep going. If you can't talk while you're exercising, you're likely working too hard.