Buzz
If you’ve ever been concerned about your heart rate during workouts being too high or too low, this is a must-read. Your 'heart rate zones' could be entirely off. These zones are not only interpreted differently across various apps, but they are also typically based on your maximum heart rate. And that maximum heart rate estimate? It’s wrong for a large portion of people.
What does it mean to determine your “maximum” heart rate?
By definition, your maximum heart rate is the highest number of beats your heart can achieve in a minute. If your watch claims your max is 180 beats per minute, but during a run, your heart rate hits 190, you haven’t exceeded your max. Instead, you’ve discovered that 180 isn’t your true maximum. Your actual max must be at least 190.
The only reliable method to determine your maximum heart rate is through rigorous physical testing. Below, I’ll outline some approaches to achieve this. Fitness devices, apps, books, and other fitness resources often bypass this step by using age-based formulas to estimate your maximum heart rate. The most common formula subtracts your age from 220.
However, this formula has significant flaws, as do the alternative equations designed to replace it. No formula can accurately pinpoint your personal maximum heart rate.
Why you should be skeptical of any maximum heart rate formula
These formulas—regardless of which one you use—are generalized calculations that provide a rough estimate of the average maximum heart rate for people of a specific age. However, averages are irrelevant when determining your individual maximum heart rate.
Consider how you shop for shoes. You wouldn’t input your height into an app and trust it to recommend a shoe size based on the average for someone of your height. Instead, you try on shoes or measure your feet. You might wear a size 6 or a size 9. The average size is meaningless, as many people have feet that are larger or smaller than the average.
The same principle applies to maximum heart rates. The concept of “calculating” a maximum heart rate has become so ingrained that many assume the results are accurate, or at least close. However, consider this graph from a 2012 study, where researchers recorded the actual maximum heart rates of more than 3,000 individuals. (The lines on the graph represent two of the supposedly more precise max heart rate formulas.)
If you’ve ever been puzzled by your own maximum heart rate, this will reassure you. For instance, I’m 44, and the “220 minus your age” formula suggests my max should be 176. Yet, during intense workouts, my heart rate often hits the 190s, and I’ve recorded over 200 multiple times using a chest strap (the most precise measurement method). According to this graph, heart rates exceeding 200 are indeed high for 44-year-olds, but they’re not uncommon and can’t be considered rare.
The same study also revealed that these formulas become increasingly inaccurate with age. Here are the averages they discovered for various age groups:
Age 19 to 29: 195 plus or minus 9.9
Age 30 to 39: 189 plus or minus 10.1
Age 40 to 45: 183 plus or minus 10.9
Age 50 to 58: 176 plus or minus 11.6
Age 60 to 69: 171 plus or minus 12.3
Age 70+: 164 plus or minus 12.4
The “plus or minus” here refers to a standard error, indicating that most individuals will fall within this range, but certainly not all. Even the formula designed to estimate the average for a specific age group fails to accurately reflect how heart rates truly vary with age. For instance, the data for my age group suggests my heart rate should be between 172-194 (instead of the standard 176 prediction). Yet, I know my maximum heart rate is 202.
While my maximum heart rate is higher than most people my age, many others have lower heart rates than the formulas predict. The key takeaway is that there’s a broad range of what’s considered normal, and the commonly used formulas become increasingly unreliable as people age. I wouldn’t rely on any heart rate calculation to accurately set personal zones or exercise goals.
Why is the formula so inaccurate?
The “220 minus age” formula was derived from limited observations, as explained in this paper on the formula’s history. The same paper points out that all subsequent formulas have similarly large error margins (plus or minus 10 beats per minute, or more in many cases—consistent with the 2012 study I mentioned earlier). “Currently, there is no acceptable method to estimate HRmax,” they stated in 2002, and this remains true today.
I feel compelled to mention the enigmatic nature of the heart, as if it’s a mystery no one can fully unravel. (Surely, a poet has already captured this sentiment.) The reality is that age alone doesn’t dictate a person’s maximum heart rate, so any age-based formula will inevitably fall short. If factors like weight or exercise habits significantly influenced your max heart rate, a more precise formula might exist. However, just as people vary in shoe sizes, their max heart rates differ for reasons we don’t fully comprehend, making this a problem math alone can’t solve.
Unfortunately, smartwatch manufacturers and other device creators need default zones to display when users first start using their products, even if those users have never pushed themselves to their physical limits. This is why these flawed calculations persist. I understand the manufacturers’ predicament: On one hand, only an intense workout can reveal your true max heart rate. On the other, most beginners are unlikely to attempt such a test and may lack the experience to pace themselves effectively. Additionally, individuals with cardiovascular, metabolic, or renal conditions should avoid all-out exercise without consulting a doctor.
What to do instead of relying on a max heart rate calculation
Given these issues, reputable organizations have largely moved away from the concept of “calculating” your max heart rate. Runner’s World removed its target heart rate calculator. The American Council on Exercise, a leading organization for personal training certifications, advises trainers against using max heart rate formulas and instead recommends real-world tests to help clients align their heart rates with appropriate exercise intensities. (As an ACE-certified trainer, I can confirm this is standard practice.)
If you’re a beginner, you don’t need a heart rate goal at all. If you can exercise comfortably without losing your breath, you’re in a suitable zone for steady-state activity. Keep it simple.
If you prefer a numerical target, try a submaximal talk test. The casual approach is to note your heart rate when speaking becomes difficult; the formal method involves this treadmill test.
If you’re determined to know your max HR, you can test it. This is best for experienced individuals, and avoid it if a healthcare provider has advised you to stick to lower-intensity workouts. Instructions are below.
How to determine your maximum heart rate
First, let me clarify what doesn’t work: starting cold and sprinting at full effort until you’re exhausted within seconds. While your heart rate will spike, it won’t come close to your true max in such a brief burst. Your heart requires time to ramp up, and sustaining a hard effort for several minutes is essential to reach your peak. With that in mind, here are a few methods to accurately measure your maximum heart rate.
Warm up, then run up a long hill three times
This is the standard protocol, famously outlined by Pete Pfitzinger in Advanced Marathoning:
Begin with a 10 to 15-minute jog to warm up.
Run hard up a moderately steep hill that’s at least a quarter-mile long (Pfitzinger suggests a 600-meter hill).
Once you reach the top, jog back down and repeat.
After three repetitions, the test concludes. The highest number recorded on your watch is your new max.
If you don’t own a smartwatch, you can check your pulse by placing two fingers on your neck after each hill repeat. The highest number you record is your max.
Warm up, then perform three four-minute intervals
This test follows a similar approach but doesn’t require a hill and isn’t limited to running. It was developed by the Cardiac Exercise Research Group at the Norwegian University of Science and Technology, the same team behind the popular Norwegian 4x4 workout. Here’s their explanation:
Start with a thorough warm-up ("until you break a sweat," they suggest). A 10 to 15-minute warm-up, as described earlier, should suffice.
Push yourself hard for four minutes (running, cycling, etc.), followed by three minutes of active recovery, such as brisk walking.
Repeat the four-minute intense interval, then another three minutes of active recovery.
Begin a final four-minute interval. After two minutes, sprint at maximum effort. Or, as they phrase it: "increase your speed even further and run until you’re completely exhausted."
The highest number displayed on your heart rate monitor (or measured manually at the end) is your max.
If you’re experienced, use a race to estimate your maximum heart rate
You might bypass field tests if you’ve participated in all-out races. However, a word of advice: this method works best if you’re experienced at racing. If you aim to run a fast mile but start too hard and fade by the end, your heart rate may never reach its true max. On the other hand, if you’ve paced your races well, you’ll likely see your highest heart rates near the finish. (My current max of 202 was recorded twice: once during a graded exercise test that pushed me to my limit, and once at the end of a 1-mile time trial on a track.)
If you begin at a challenging pace and gradually increase your speed, finishing with a near-sprint, you’re likely to hit or come close to your max heart rate. An FTP test on a bike or a 5K race often follows this pattern. So, if you’re an experienced runner or cyclist, you can likely use the heart rate from your last hard race as a close approximation of your max.
Keep in mind that your max heart rate for running may differ from other activities like cycling or, notably, swimming. Your heart works harder when you’re upright compared to being horizontal. If you determine your max heart rate through a running test and apply it to swimming, you’ll be aiming for numbers that are unattainable in the pool.
Ultimately, heart rate numbers are only as valuable as the training they inform. Whether you should use heart rate percentages for your workouts depends on whether these calculations help you improve your speed, strength, and health. If you perform better without numbers, that’s perfectly fine; if you do use them, ensure they’re accurate.
