One Simple Rule For Burning Fat Faster
You've probably been told that the best way to predict your maximal
heart rate — the maximum number of times your heart can beat each
minute — is to subtract your age from the number 220.
But where does the formula for calculating your maximum heart rate actually
come from?
Can it be trusted?
And if you're trying to lose weight, should you use it to work out your "fat burning" zone?
Here's the surprising true story of the popular (but flawed) 220 minus age formula...
Although scientists have been attempting to predict maximal heart rates since the late 1930's, the 220 minus age formula originated in the late sixties.
In subsequent years, the
formula has become immortalized in charts on every gym wall, on cardiovascular
exercise machines, and even in medical textbooks.
But when Gina Kolata, science writer for The New York Times,
did a little detective work, she was astonished to
find that the formula was meant only as a rough guideline and NOT
as the precise measurement often used by serious athletes to gauge
their progress via heart rate monitors.
In her book Ultimate Fitness:
The Quest for Truth about Exercise and Health, Kolata asked Dr.
William Haskell
— the exercise physiologist who came up with the formula — to
tell his story...
It was 1968, Haskell said, and he had recently gotten his Ph.D. in exercise
physiology and was employed by the U.S. Public Health Service, one of
thousands of doctors and scientists who work in government offices and
laboratories under the direction of the Surgeon General.
His job put
him under the supervision of Sam Fox, a doctor who was the head of
a major heart-disease prevention program in the Public Health Service.
Fox had been invited to give a talk at a World Health
Organization meeting on the use of exercise testing to detect heart
disease. So he asked Haskell to help him prepare, sending him to
the library to gather papers in which people of different ages had been
tested to find their maximum heart rates. Haskell found seven papers
and plotted the data on a piece of graph paper.
Shortly afterward, while they
were sitting together on a long airplane ride, Haskell pulled out his
plot and showed it to Fox.
"We drew a line through it and I said
'Gee, if you extrapolate that out, it looks like at twenty, your maximum
heart rate is two hundred, at age forty it's a hundred and eighty,
at sixty it's one-sixty..."
Fox, he says, turned to him and
said, "It
looks like 220 minus your age."
In 1971, Fox and Haskell published
a graph based on ten studies, rather than the original seven, along
with their formula. They concluded, once again, that the formula maximum
heart rate equals 220 minus age best fit the data.
But how accurate is it... really?
Although the 220 minus age formula is the one that most people use to estimate their maximum heart rate, there are some big question marks over its accuracy.
In 2001, Dr. Douglas Seals, an exercise physiologist at the University
of Colorado, tried to improve the formula, gathering data from 351 published
studies involving 18,712 people [1]. To that he added his own data from
studies involving 514 men and women, aged 18 to 81.
His research, published in the American Journal
of Cardiology, shows that the traditional formula
of 220 minus age overestimates the maximum rate in young adults,
does a pretty good job for people who are around forty years old, and
then increasingly underestimates the maximum rate 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 came up with a very similar formula (HRmax = 207 - 0.7 x age) [2].
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
|
|
20
|
200
|
194
|
|
30
|
190
|
187
|
|
40
|
180
|
180
|
|
50
|
170
|
173
|
|
60
|
160
|
166
|
|
70
|
150
|
159
|
|
80
|
140
|
152
|
|
90
|
130
|
145
|
Yet Seals, despite his impressive and
exhaustive effort to get accurate data and derive a better formula, has so far failed
to replace the old equation suggested by Haskell and Fox.
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, adding, "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. Interestingly, when Dr. Robert Robergs analyzed
the data on which the original formula was based, he ended up with
a totally different equation!
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. Which means that what you calculate as your training zone could be completely wrong.
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.
If you want to use heart rate training zones, go and find an exercise physiologist who can put you through a graded exercise test. This will tell you what your TRUE maximum heart rate is and allow you to create heart rate training zones that are tailored specifically to you.
What about the so-called "fat burning" zone?
Most cardiovascular exercise machines have special "fat burning" programs, which change the difficulty level of the exercise depending on your heart rate.
It's true that your body burns less fat as your exercise intensity increases, such as when you move from a walk to a run. But it's wrong to conclude that exercising at this lower intensity is the best way to lose weight.
Quite apart from the error involved in calculating the numbers in the first place, the whole concept of a "fat burning zone" has one big flaw that renders it completely irrelevant for most people. If you want to lose weight, the best thing to do is focus on burning as many calories as you can in the time you have
available.
About The Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you're stuck
in a rut with your current exercise and diet plan... fed up with
only losing a pound here and there... or still skinny after months
(or even years) of trying to build muscle and gain weight... click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
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Reference
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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