Here’s the real story on how the formula for calculating your max heart rate came about… taken from the NY Times Health.

The common formula was devised in 1970 by Dr. William Haskell, then a young physician in the federal Public Health Service and his mentor, Dr. Samuel Fox, who led the service’s program on heart disease. They were trying to determine how strenuously heart disease patients could exercise.

In preparation for a medical meeting , Dr. Haskell culled data from about 10 published studies in which people of different ages had been tested to find their maximum heart rates.

The subjects were never meant to be a representative sample of the population, said Dr. Haskell, who is now a professor of medicine at Stanford. Most were under 55 and some were smokers or had heart disease.

On an airplane traveling to the meeting, Dr. Haskell pulled out his data and showed them to Dr. Fox. ‘‘We drew a line through the points and I said, ‘Gee, if you extrapolate that out it looks like at age 20, the heart rate maximum is 200 and at age 40 it’s 180 and at age 60 it’s 160,’’ Dr. Haskell said.

At that point, Dr. Fox suggested a formula: maximum heart rate equals 220 minus age.

But, exercise physiologists said, these data, like virtually all exercise data, had limitations. They relied on volunteers who most likely were not representative of the general population. ‘‘It’s whoever came in the door,’’ Dr. Kirkendall said.

In addition, he and others said, gauging maximum heart rates for people who are not used to exercising is often difficult because many prematurely stop the test.

As the treadmill hills get steeper, people who are not used to exercise will notice that their calves are aching. ‘‘They will say they can’t go any further,’’ Dr. Kirkendall said.

In addition, Dr. Wilmore, the exercise physiologist, said it was clear from the scattered data points that maximum heart rates could vary widely from the formula. ‘‘If it says 150, it could be 180 and it could be 120,’’ Dr. Wilmore said.

Can you imagine if your MHR (Maximum Heart Rate) was 160, but according to the formula your MHR was supposed to be 185?  You could push your self until you passed out and still not reach your calculated MHR. Or, on the other hand, what if your MHR was actually 200, but the formula calculated it to be 180?  You would always be training at sub-par intensities, wondering why the people around you were sweatin’ up a storm when you barely broke a sweat.

The truth is that the popularity of the formula was more about timing than about exact science.  It was available at just the right time, when people wanted an easy way to objectively figure out an intensity that would satisfy filling the criteria for both the medical field as well as the fitness field.

...But the formula quickly entered the medical literature. Even though it was almost always presented as an average maximum rate, the absolute numbers took on an air of received wisdom in part, medical scientists said, because the time was right.

Doctors urging heart patients to exercise wanted a way to gauge exercise intensity. At the same time, exercise gurus, promoting aerobic exercise to the public, were asking how hard people should push themselves to improve their cardiovascular fitness. Suddenly, there was a desire for a simple formula to estimate maximum heart rates.

‘‘You tell people to exercise at a moderate intensity,’’ Dr. Haskell said. ‘‘Well, what’s a moderate intensity?’‘

Soon, there was a worldwide heart-rate monitor industry, led by Polar Electro Inc, of Oulu, Finland, selling more than 750,000 monitors a year in the United States and citing the ‘‘220 minus your age’’ formula as a guide for training.

The formula became increasingly entrenched, used to make graphs that are posted on the walls of health clubs and in cardiology treadmill rooms, prescribed in information for heart patients and inscribed in textbooks. But some experts never believed it.

Dr. Fritz Hagerman, an exercise physiologist at Ohio University, said he had learned from more than three decades of studying world class rowers that the whole idea of a formula to predict an individual’s maximum heart rate was ludicrous. Even sillier, he said, is the common notion that the heart rate is an indication of fitness.

Some people get blood to their muscles by pushing out large amounts every time their hearts contract, he said. Others accomplish the same thing by contracting their hearts at fast rates. As a result, Dr. Hagerman said, he has seen Olympic rowers in their 20’s with maximum heart rates of 220. And he has seen others on the same team and with the same ability, but who get blood to their tissues by pumping hard, with maximum rates of just 160.

’‘The heart rate is probably the least important variable in comparing athletes,’’ Dr. Hagerman said.

So what is the best way to find out how hard you need to train, without going into the danger zone?  Well, you have a couple of options.

1. You can calculate your own maximum heart rate (MAX HR) which is by far the most accurate method

2. You can use an updated MAX HR formula, which is less accurate but easier

3. You can simply go by how you feel which is suggested for anyone that’s not new to working out and knows their body well

Well, I’m a big fan of short high intensity training, and I’ve been working out long enough to know how much I can push my body without hurting myself.  So I don’t use heart rate monitors often, BUT I still use them on days when I need to make sure that I’m recovering.  And for people that aren’t tuned in to their body as well, or like to follow more exact protocols, I think using a heart rate monitor is very helpful.

According to the scientists at Norwegian University of Science and Technology the traditional formula can underestimate your MAX HR by up to 40 bpm in seniors, and this formula starts becoming inaccurate between ages 30 to 40 years.  So they came up with a more accurate formula based on a study conducted on 3320 healthy adults between 19 - 89 years old.

Here’s the new formula:  211 - (0.64) x age.

So at 40 years old, your maximum heart rate is 211 - (0.64) x 40 = 185 bpm

Although the new formula is supposed to be more accurate, it’s important to keep in mind that the study found large maximum heart rate variations within each age group.  They also found that genetics played a much bigger role in your MAX HR than physical fitness levels.  So if you want a reliable number, you really need to find out your own maximum heart rate (MAX HR).

How to calculate your own MAX HR.

You’ll need a heart rate monitor for this method.  I would recommend either choosing a stationary bike or treadmill for this test.  Bike is the safest modality.

1. Warm up thoroughly.  I suggest spending about 5 minutes until you break a light sweat.

2. Run or Bike for 4 minutes.  You should be too out of breath to talk.

3. Active rest - walking or easy cycling for 3 minutes.

4. Run or Bike for 4 minutes.  You should be too out of breath to talk.

5. Active rest - walking or easy cycling for 3 minutes.

6. Run or Bike for 2 minutes at which point run or bike as fast as you can until you reach exhaustion and can’t continue.

7. Immediately take your heart rate.  This is your MAX HR.

This method may take a little time and effort, but it’s well worth doing if you’re going to use a heart rate monitor to workout.  When you’re doing high intensity workouts, it’s imperative that you work out at 85 - 90% your MAX HR, anything lower and your not getting benefits of the workout.  Remember, intensity trumps duration when you’re trying to get lean and burn as much fat as possible.

But perhaps more importantly, knowing your MAX HR and having a heart rate monitor becomes really helpful during your rest intervals.  According to Dr. Michael Lauer, a cardiologist and the clinical researcher at The Cleveland Clinic Foundation, how quickly your heart rate goes down is a much better indication of how fit you are.  A normal individual’s heart rate should drop about 20 bpm (beats per minute) every minute and and athlete’s HR can drop up to 50 beats a minute.  In a nutshell, the fitter you are the faster your heart rate goes down.

And here’s another tip, if you’re feeling sluggish and tired, check to see how quickly your HR comes down between sets.  If you’re body hasn’t recovered enough, you’ll notice that your HR doesn’t come down as much during your rest intervals either.  If that’s the case, it may be a good idea to lower your intensity of the workout to give you body a break or take longer rests between sets so you have more time to recover.