Measuring your target heart rate (THR) is a concrete, numbers-don’t-lie way to sneak a peek inside your body to find out what exercise intensity is right for you. In fact, it may be the piece of data that finally convinces you not to push too aggressively during your cardio routine—or not take it so easy that you barely get your heart rate up. Not everyone is meant to work out the same way, and figuring out your target heart rate can give you a clearer sense of just how hard you should push yourself to improve your health and fitness.
Heart Rate and Your Health
During aerobic exercise, your heart, lungs and circulatory system are called on to deliver oxygen and nutrients to the muscles you’re engaging. Your heart rate is one way to measure just how hard your body is working to do all of that.
When you regularly perform aerobic exercise at a challenging intensity, elevating your heart rate, you reduce your risk of obesity, heart disease, type 2 diabetes and other health conditions. Even your brain health can improve. Considering this, you may think that working out harder is always better. But reaching your maximum heart rate—the greatest number of beats per minute your heart can possibly achieve during exercise—requires an all-out effort that is extremely uncomfortable and impossible to maintain; even the most highly trained athletes can only maintain this intensity for a few minutes at a time. In addition, exercising at or near your maximum heart rate has not been shown to have significant benefits. In fact, it can actually be risky because of the stress it puts on your heart.
By knowing your target heart rate you assure yourself that you optimize fitness improvement, calorie- and fat-burning, and you prevent overdoing it and not having fun during exercise.
How to Calculate Your Target Heart Rate
Your target heart rate (THR zone) is 70 to 85 percent of your maximum heart rate, which must be determined before you can zero in on your target range.
You may have seen simple formulas for determining maximum heart rate, or even charts that give a suggested THR based on gender and age. While these may seem somewhat helpful for general reference, they can be very inaccurate. Because both options serve the masses and use age as their only reference point, they can be off by as much as 30 beats per minute in estimating maximum heart rate. That’s why you’ll need the help of your exercise physiologist or doctor to determine your THR—the intricacies of the human body simply vary too much from person to person to use one-size-fits-all formulas.
- Submaximal Exercise Test: You put on a heart rate monitor and begin exercising on your preferred cardio machine, like a treadmill, elliptical or stationary bike. Your exercise physiologist increases your intensity every two minutes for about 15 minutes total. By observing the feedback on your heart rate monitor and checking in on your exertion level—your breathing rate, whether you can talk without huffing and puffing, your comments on how you’re feeling—as you go, he can gauge when he thinks you have reached 70 percent and 85 percent of your maximum heart rate—this is your target heart rate zone.
- VO2 Maximum Test This test is the gold standard for determining your target heart rate. While on your choice of a treadmill, elliptical or stationary bike, you wear a heart rate monitor and a portable device called a metabolic analyzer, which takes samples of your breath and measures how much oxygen you consume and how much carbon dioxide you expel and as you work at incrementally more challenging workloads. Your exercise physiologist will stop the test once you have had enough—ideally when you are at 90 percent to 95 percent of your maximum effort. The test also measures your VO2 maximum, your anaerobic threshold and how many calories you burn at any given heart rate.
- Cardiovascular Stress Test Your cardiologist usually performs this test when she wants to determine whether your heart can safely tolerate aerobic exercise. Twelve electrodes are placed in specific positions on your chest. You then exercise while your doctor watches the electrocardiogram (EKG), which traces how your heart beats, and takes your blood pressure every two minutes. The test also tracks your heart rate, which your physician will use to estimate your maximum heart rate, and then determine your THR. This test is typically performed on men over 45 and women over 55 who have never had a stress test or are risk for cardiovascular disease or heart attack.
Using Your Target Heart Rate
A portion of your workout—usually your warm-up and cool-down—should be spent below your THR, or at about 50 to 65 percent of your maximum heart rate. And, you guessed it: Part of your workout should be spent in your target heart rate zone, or about 70 percent to 85 percent of your maximum heart rate. Your exercise physiologist can help you determine how long to spend in each range in your various workouts, depending on your fitness level and goals.
Aim to be at your THR for at least 15 to 20 minutes workout time, and ideally 35 to 45 minutes. If you’re a beginner, start at 65 percent to 70 percent of your maximum heart rate and gradually increase the intensity. If you find it challenging to reach that number at first, give yourself points for exercising and remember that, with time, your stamina will improve.
You have probably noticed that some of the cardio machines at your gym are equipped with hand sensors that you can grip tightly for a heart rate measurement. You can use them, but just keep in mind that their readings tend to be inaccurate. Remember…
- Before you begin any exercise program, discuss it with your physician. And be cautious if you have a heart condition and/or take a beta-blocker medication. It will lower your heart rate whether you are at rest or exercising, which means that your maximum heart rate and target heart rate zone will be significantly lower than charts will predict it to be. Do not try to achieve chart predicted heart rates.
- More is not necessarily better. If your workout feels uncomfortably strenuous, regardless of your heart rate, slow down.
- Finish out your workout with a brief cool down. Gradually decelerate to an easy pace, until your breathing rate has slowed to near normal. End with a few minutes of gentle stretching to keep muscles limber.