Your “maximum Heart Rate” Is Probably Incorrect

If you’ve ever worried about your heart rate getting too high or too low during a workout, you’ll want to read this. Your “heart rate zones” may be completely wrong. Not only are zones defined differently across different apps , but they’re usually calculated based on your maximum heart rate. And that maximum heart rate calculation? This is not true for large swaths of the population.

What does it mean to know your “maximum” heart rate?

Maximum heart rate, by definition, is the fastest rate your heart can beat. If your watch tells you that your maximum is 180 beats per minute, and then you go for a run and your heart beats at 190 beats per minute, you have not exceeded your maximum. You just discovered that 180 is not your maximum at all. Your actual maximum should be at least 190.

The only way to truly know your maximum heart rate is to test it through intense exercise. Below I will tell you several ways to do this. Meanwhile, fitness gadgets and apps (and in the old days, books and other sources of fitness advice) try to skip this step by using a formula that estimates your maximum heart rate based on your age. The most popular formula simply subtracts your age from 220.

But there are problems with this formula and even with the alternative equations that have been proposed in its place. There is no formula that can tell you what your personal maximum heart rate actually is.

Why you shouldn’t trust maximum heart rate formulas

These formulas—no matter which one you choose—are universal calculations that will be approximately accurate for determining the average maximum heart rate of people of a certain age. But it doesn’t matter what the average is if you’re trying to determine the maximum heart rate for you as an individual.

Think about how you buy shoes. You don’t tell an app you’re 5’6″ and then trust it if it says the average 5’6″ person wears a size 8 shoe. You need to try on different shoes or at least measure your feet. Maybe you’re a size 6. Maybe you’re a size 9. It doesn’t really matter what size the average person wears because many people have larger or smaller feet than the average person.

The same goes for maximum heart rate. The idea of ​​”calculating” your maximum heart rate has become so common that people assume the calculation is correct, or at least very close to it. But take a look at this graph from a 2012 study in which researchers measured the actual maximum heart rates of more than 3,000 people. (The lines represent two supposedly more accurate maximum heart rate formulas.)

If you’ve ever wondered about your maximum heart rate, this will help you feel grounded. For example, I’m 43 years old, and the formula “220 minus your age” would lead me to believe that my maximum is 177. But with heavier workouts, my heart rate usually reaches 190, and I’ve gone over 200 several times with a chest strap. Looking at this graph, a heart rate of 200+ is certainly high for a 43 year old, but it’s not unheard of or even rare.

The same study also found that formulas become even more inaccurate as people age. Check out the averages they found for different age groups:

• Ages 19 to 29: 195 plus or minus 9.9.

• Ages 30 to 30: 189 plus or minus 10.1.

• Ages 40 to 45: 183 plus or minus 10.9.

• Ages 50 to 58: 176 plus or minus 11.6.

• Ages 60 to 69: 171 plus or minus 12.3.

• Age 70+: 164 plus or minus 12.4.

“Plus or minus” in this sense refers to the standard error, meaning that most people fall within this range, but by no means all . So even a formula that is supposed to find the average for a given age doesn’t take into account how people’s heart rates actually change as they age.

And while I have a higher maximum heart rate than most people my age, there are also many people whose heart rates are lower than the formulas predict. As a result, not only is there a wide range of normal values, but general formulas are becoming less and less accurate in older adults. I don’t believe any heart rate calculation is accurate enough to set your personal zones or exercise goals.

How can the formula be so wrong?

The “220 minus age” formula was based on observations from sparse data, as detailed in this article on the history of the formula . The same article notes that all formulas developed since then have similarly poor error rates (plus or minus 10 beats per minute, and in many cases more, consistent with the above). “There is currently no acceptable method for estimating maximum heart rate,” they wrote in 2002, and that remains true today.

I feel that I must say something here about the unknowability of the mysteries of the heart. (Surely some poet beat me to it.) The truth is that age alone does not determine a person’s maximum heart rate, so no matter what numbers you use to create an age formula, you simply won’t get a useful result. If there were other obvious relationships, such as if your weight or exercise habits affected your maximum, a more precise formula would undoubtedly be possible. But people have different heart rates for reasons we don’t fully understand, just like they differ in shoe sizes, so math can’t solve the problem.

Unfortunately, manufacturers of smartwatches and other devices want to have some default zones that will show up when you start using their product, even if you’ve never done a max effort sprint in your life. This is why we keep seeing these erroneous numbers over and over again. I can understand the dilemma of smartwatch manufacturers: on the one hand, only intense training will determine your real maximum. But on the other hand, most beginners will not want to take intensive tests and will have no idea how to properly pace themselves to reach their maximum anyway. People with cardiovascular, metabolic, or kidney disease should not engage in vigorous exercise unless they first consult a doctor .

What should you do instead of relying on your maximum heart rate calculation?

Because of the above issues, reputable organizations have largely abandoned the idea of ​​”calculating” maximum heart rate. Runner’s World has removed its target heart rate calculator . The American Council on Exercise, one of the largest personal training certifying organizations, instructs trainers not to use maximum heart rate calculations , but to conduct real-life tests to help clients match their own heart rate to the appropriate exercise intensity. (I am ACE certified and can confirm that this is what the textbook says.)

• If you’re a beginner, you don’t need a heart rate target at all ; if you can exercise without getting out of breath, you’re in the good “zone.” You don’t need to think too much about it.

• If you want to evaluate this, you can do the Submaximal Speaking Test . An informal way is to simply notice what number you see on your watch when you can no longer speak comfortably; a more formal way is the treadmill test, which achieves the same thing .

• If you really want to know your maximum heart rate, you can check it out . I would only recommend this to relatively experienced people, and would obviously skip it if a medical professional has ever advised you to stick to low-intensity exercise.

How to check your maximum heart rate

While we tend to equate “heart rate” with “effort,” maximal effort during exercise does not always result in maximal heart rate. You want this hard effort to continue for at least a few minutes as you push harder and harder.

That’s why it’s helpful to have racing experience to pass one of these tests. If you set out to run a fast mile, but you run too hard at the beginning and slow down towards the end, your heart rate may never reach its true maximum. On the other hand, if you start at a fast pace and then pick up the pace a little as you go and finish in an extended sprint as you get closer to the finish line, you will reach your maximum or something very close to it. An FTP bike test or 5K run will often look like this, so if you’re an experienced runner or cyclist, you can probably just look at your heart rate during your last hard race and assume that number is higher. or less than your maximum.

All this to say, you’re reading this far because you want to do some field testing, right? Here is a common protocol that is best known by Pete Pfitzinger in the book The Advanced Marathon .

1. Jog for 10 to 15 minutes to warm up.

2. Run hard up a moderately steep hill that is at least a quarter mile long (Pfitzinger recommends a 600-meter hill).

3. Once you get to the top, run back down and repeat.

4. After three repetitions, the test is over. The highest number recorded by your watch is your new high.

If you don’t have a smartwatch, you can take your heart rate with two fingers on your neck at the top of each hill rep. The highest number you see is your maximum.

Note that your maximum heart rate for running may be different from the maximum heart rate for other sports such as cycling and, most famously, swimming. Your heart has to work harder to pump blood when you’re upright rather than horizontal. If you determine your maximum heart rate using a running test and then use it to train in the pool, you’ll be chasing numbers that you can’t actually achieve in the pool.

However, heart rate metrics are only as good as the workouts they guide you to, so whether you should use heart rate percentages to guide your workouts depends on whether those math-guided workouts are helping you get faster, stronger, and healthier . If you work best without numbers, that’s fine; if you use numbers, make sure they are accurate.

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