The Biggest Problem With Using Max Heart Rate for Training
Some “facts” survive by repetition. This is called the illusory truth effect, which states that if you say something often enough, our brains start assuming it must be true.
For example:
- We only use 10% of our brains.
- Chewing gum takes seven years to digest.
- Cracking your knuckles causes arthritis.
- Cold weather gives you a cold.
All proven false. But repeat them for decades, and we stop questioning.
One more that hangs on the wall at almost every rec center is the formula for max heart rate.
Max HR = 220 − age.
This one has been perpetuated for over 50 years. Even organizations like the American Heart Association claim it as fact.
I’ve found that this can really stress people out, because it’s nowhere near precise enough to guide your training, along with the underlying concern that one's heart might explode.
Especially for athletes like me, who at age 40 will regularly blow past my predicted max, and will touch 205 on a hard workout.
Why the Formula Falls Apart
Every resource on the topic I could find pointed back to an article printed in 1971 by Fox, Naughton, and Haskell.
I spent a good amount of time trying to dig this up, but had no luck.
But what I’ve gathered is that it was back-of-the-napkin math (lacked any mathematical equations) using mixed datasets from different labs, protocols, and populations, which landed on this rough estimation for determining one's maximum heart rate.
It didn’t include any peer review either. It was just a rough estimate that stuck.
Since then, others have tried to improve on it:
Tanaka: 208 – 0.7 × age
Gellish: 207 – 0.7 × age
Nes: ~211 – 0.64 × age
All of them show HRmax does decline with age, but not as much as one beat per year.
But most importantly, individuals vary greatly!
When researchers compared the formulas to verified lab tests, the errors were huge. The standard error was 12 beats per minute in either direction, or in my case, underestimating my max by more than 20 bpm.
How to Actually Measure Your Max Heart Rate
Training does lower your resting and sub-max heart rate because your heart pumps more blood with each beat, but your true ceiling usually stays the same or even drifts 1–3 bpm lower with endurance training (because a bigger, stronger heart needs more time to fill).
So understand that your maximum heart rate is not really a fitness standard any more than your shoe size—getting fitter doesn’t raise your max heart rate. It's mostly set by age and genetics.
Still, knowing your maximum heart rate is extremely helpful to your fitness by helping set your training intensities. And just like you wouldn’t base your strength training on maxes from broad population estimates, you shouldn’t base your heart rate thresholds on this either.
Here is a simple (but uncomfortable) field test outlined by Polar:
1. Warm up for 15 minutes.
2. Find a hill you can run or ride for at least 2 minutes.
3. Run it three times, making it progressively harder each round:
- First: A pace you could hold for ~20 minutes.
- Second: Faster, a pace you could hold for 10 minutes. Note your peak HR, your max will probably be about 10 beats higher.
- Third: All-out, ~1 minute. This should bring you right to HRmax.
4. Cool down for 10 minutes.
However, if you're going to do this, wrist-based heart rate readings aren't always the most accurate. You're better off using a chest strap.
And if you’d rather avoid an all-out test, you can estimate your threshold heart rate from a 30–40-minute hard effort and take the average HR from the last 20–30 min.
This is called your Lactate Threshold, and many consider it a more useful measurement for determining training thresholds. However, variables such as caffeine, recovery, hydration, heat, and humidity will affect your HR response during this sort of effort. Something to keep in mind when you're establishing your training zones.
And lastly, you're body has some effective protective mechanisms that stop your effort before your heart redlines. I previously ran treadmill stress tests for a cardiology practice, and in over 15,000 tests, nobody keeled over because their heart was pushed beyond its limit.
However, cardiac symptoms do tend to reveal themselves when pushed to the max.
Which brings me to my disclaimer, don't fret intense efforts even if your heart rate goes beyond some number on a chart. But if you feel any abnormalities, even if they don't appear to be "heart-related," get them checked out.
Originally published as Movement #276
