One of the “personal training 101” topics that all fitness professionals need to know is how to determine a maximum heart rate. For most people, this means learning the 220 – Age equation. While this equation is used by millions of people for decades, other equations—that are said to be better —also exist. In fact, the 8th edition of the ACSM's guidelines book, for the first time, has covered one such alternative heart rate equation. Endorsement by the ACSM carries a lot of weight which means it may not be long before all other personal trainer books start including it as well. This means trainers need to know it. With that in mind, let's review the traditional heart rate equation and this new equation and see what we can discover.
The Old Equation
This is the equation that is in every exercise science book I own and it's also the equation used by most bikes, elliptical, treadmills etc found in gyms around the world.
Anytime a treadmill asks you your age, this is the equation it's likely using.
Basically this how the equation works.
Suppose you are a 40 year old person (it doesn't matter if you are a man or woman) and you want to exercise on the treadmill at 60-80% of your maximum heart rate ability.
According to this equation, 220 – 40 = 180 heart beats per minute (bpm).
In theory, this means that a 40 year old heart will beat a maximum of 180 times in a minute, if the person exercises exercise as hard as they can. This is called the maximum heart rate or Heart Rate Max (Max HR).
Since, in this example, you want to exercise at 60% and 80% of the maximum, the target heart rate is calculated this way:
180 X 0.6 = 108 bmp
180 X 0.8 = 144 bpm
Tip: to change a percent to a decimal, just move the decimal point two places to the left. Hence, 60.% becomes 0.6 and that’s all you have to do.
Answer: you should maintain a target heart rate of between 108 bmp and 144 bpm
Pretty easy right?
But, the big problem here is that answer provided by the 220 – age equation is just an estimation. Your real max heart rate is not exactly 220-your age.
This is why other max heart rate equations exist. Let's look at one of the most popular equations
Trivia. Where did the “220” come from in the equation? Does a baby's heart beat 220 times a minute. No it doesn’t. I cover the history of the 220 -age equation in my book, Personal Fitness Training Beyond the Basics.
The New Heart Rate Equation
On page 155 of the ACSM Guidelines For Exercise Prescription (8th edt), another maximum heart rate equation is mentioned. Here is the equation:
206.9 – (0.67 X age)
The ACSM says this equation is “the most accurate” of the various maximum heart rate equations you may have heard of.
This equation looks a bit more complicated than “220 – Age” but it's not too bad. Let's take a look at it by keeping with our 40 year old person example from above.
Do the work in the parentheses first:
206.9 – (0.67 X 40) = 206.9 – 26.8. This equals 180.1 bpm. Lets round down to 180 bpm.
So the maximum heart rate is 180 bpm.
Notice that this is the same answer we obtained from the 220 – Age equation.
Question: is it always the same? Keep reading…
Then, if we wanted to calculate a target heart rate for this person, it's just like we did above. Let's use 60% and 80% again:
180 x 0.6 =108 bpm
180 X 0.8 = 144 bpm
The table below compares estimated maximum heart rates (in bpm) calculated from both equations.
220 – Age
206.9 – (0.67 x Age)
As you can see, the answers are pretty much the same at age 40 but for other ages they do not give the same maximum heart rates.
The 206.9 – (0.67 X Age) will give a more accurate answer to the maximum heart rate question, but since it’s a little more complicated, I'm sure the 220- Age equation will prevail in gyms, at least until this new equation catches on.
All that said, no matter which heart rate equation people use, I am still of the opinion that personal trainers don’t need to bother with any of them for the majority of their clients. I say this because I feel better alternatives include using the Talk Test and RPE scale (Borg Scale). These other methods require no math also work much better for people who are taking medications for high blood pressure/heart disease, many of which are likely the clients of personal trainers.
What do you think?