Beta blockers are a class of medications used to treat conditions that include heartbeat abnormalities, heart failure, chest pain and high blood pressure, states MayoClinic.com. When you take beta blockers, they slow your heart rate, and this heart rate decrease may change your body's reactions to exercise. However, your doctor cannot tell in advance exactly how much beta blockers will affect you, so know your risks and notify your doctor of abnormalities, MayoClinic.com explains.
Beta Blocker Basics
Beta blockers achieve their effects by stopping adrenaline in your body from affecting substances in your heart called beta receptors, according to the Texas Heart Institute. Normally, beta receptors help control the ways nerve impulses travel through your heart, and blocking their actions will slow these impulses. The net effect of these slowed impulses is a decrease in your heart's need for blood and oxygen; in turn, THI indicates, this reduced need allows your heart to perform its job with less effort. Commonly available beta blockers in the U.S. include metoprolol, sotalol, esmolol, propanolol and nadolol.
Heart Rate and Exercise
When you exercise, you can track the exertion placed upon your heart with a measurement called target heart rate, according to the American Heart Association. To determine your target heart rate, you must first estimate your heart's maximum level of safe exertion, also called your maximum heart rate. You can determine this maximum rate by subtracting your current age from the number 220. For example, if your age is 45, you have a maximum safe heart rate of 175, which means your heart can beat a maximum of 175 times per minute during exercise. Depending on your current level of fitness, your target heart rate during exercise is anywhere from 50 to 85 percent of your maximum rate, the AHA indicates.
Beta Blocker Effects
If you exercise while taking beta blockers, the medication-related decrease in your heart rate can make it impossible for you to reach your normal target heart rate, according to Dr. Sheldon G. Sheps of the Mayo Clinic. This holds true regardless of the effort you put out during exercise. However, your doctor can't predict in advance how much your medication will affect your target rate. To determine the effects of a beta blocker, you will need to undergo a procedure called an exercise stress test, which measures your heart's reactions in a highly controlled exercise environment. Using the results of a stress test, MayoClinic.com says, your doctor can appropriately recalculate your target heart rate.
Resting Rate Calculations
You can also roughly calculate your new target heart rate by calculating your medication's effects on your heartbeat during periods of rest, MayoClinic.com reports. For instance, if a beta blocker has dropped your resting heart rate by 10 beats per minute, you can also drop your pre-medication target heart rate by 10 beats. However, a beta blocker can affect your target rate more severely than it affects your resting rate, and using a resting rate calculation may not allow you to properly safeguard your health.
If you want to exercise while taking a beta blocker and have not undergone an exercise stress test, you can estimate your effort with self-perceived judgments of your effort, fatigue and breathlessness, MayoClinic.com explains. Talk to your doctor before using this approach.