You’ve probably been told that the best way to calculate your maximum heart rate — the maximum number of times your heart can beat each minute — is to subtract your age from the number 220.
Most cardiovascular exercise machines have special “fat burning” programs, which change the difficulty level of the exercise depending on your heart rate.
But where does the formula actually come from? Can it be trusted?
In her book Ultimate Fitness: The Quest for Truth about Exercise and Health, science writer for the New York Times Gina Kolata asked Dr. William Haskell — the exercise physiologist who came up with the formula — to tell his story.
[The formula] orginated in the late sixties when William Haskell, an exercise physiologist who is now at Stanford University, and Sam Fox, a cardiologist, provided a formula for maximum heart rates for people who were having treadmill stress tests for heart disease.
Their paper, published in 1970 in a book, Research Conference on Applied Work Physiology, was not really a scientific effort; rather, it was a suggestion, based on a decidedly nonrandom and small sample of people, that the 220-minus age formula might best fit the data points.
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Haskell is a bit taken aback by the way the heart rate formula has come to be viewed almost as a physical law.
“I’ve kind of laughed about it over the years,” he says, “It’s typical of Americans to take an idea and extend it way beyond what it was intended for.”
When he and Fox proposed the formula, they never intended to give an absolute number for athletes or people who are used to exercising vigorously.
In fact, it is clear from the widely scattered data points on the graphs of heart rates that any individual’s maximum heart rate can vary widely from what that formula predicts, by as many as thirty beats per minute higher or lower.
And that means that what you calculate as your training zone could be completely wrong.
In 2001, Dr. Douglas Seals, an exercise physiologist at the University of Colorado, tried to come up with a more accurate formula, gathering data from 351 published studies involving 18,712 people . He also included data from a number of his own studies involving 514 men and women.
His research, published in the American Journal of Cardiology, shows that the traditional formula of 220 minus age overestimates the maximum heart rate in young adults, does a reasonable job for people who are around forty years old, and then becomes less accurate as people get older.
A much more accurate formula, he says, is 208 minus age times 0.7 (HRmax = 208 – 0.7 x age). In a more recent study, Oakland University researchers also came up with a very similar formula (HRmax = 207 – 0.7 x age) .
The table below shows you the difference between predicted maximal heart rates obtained using both the new and old equations.
|Age||Old formula||New formula|
If you want to train at a given percentage of your maximum heart rate, you’re better off ignoring what the exercise machines tell you and using a more accurate formula (e.g. HRmax = 207 – 0.7 x age).
But even then, individuals vary so much that your true maximum could be as much as twenty beats per minute higher or lower than the number the formula provides.
In other words, if it says 140, it could be as high as 160 or as low as 120.
Despite this, the fitness industry still seems “stuck” on the idea of using an age-based formula to calculate training intensity.
You’ll find books filled with charts, graphs and complicated training schedules, all based on the 220 minus age formula.
And while it might all look very scientific, it’s not too useful if it’s based on the wrong number.
1. Tanaka, H., Monahan, K.D., & Seals, D.R. (2001). Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology, 37, 153-156
2. Gellish, R.L., Goslin, B.R., Olson, R.E., McDonald, A., Russi, G.D., & Moudgil, V.K. (2007). Longitudinal modeling of the relationship between age and maximal heart rate. Medicine and Science in Sports and Exercise, 39, 822-829
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