A recent issue of the medical journal Circulation published an important study by Dr. Martha Gulati and her colleagues from Northwestern University. They measured heart rate responses to exercise stress tests in over 5,437 women (average age 52). After a 16-year follow up (in which 549 women – a very high and alarming 10 percent – died of various causes), the researchers found an important association between the maximum exercise heart rates and age, and they determined a better max heart-rate formula for women undergoing stress tests to help predict those at higher health risk.
But the media, as is often the case with newly published medical studies, have leaped to a number of misleading conclusions. Foremost is this: Women who exercise now have a new max heart-rate formula. But the formula determined by this study does not definitively show a woman’s maximum heart rate; it’s only an estimate. The study also does not replace the old 220-formula, since this formula has been shown to be inaccurate in determining maximum heart rate in both men and women. Finally, the Northwestern study and the formula do not provide any new information about the best exercise heart rate for woman.
While the study was important because it provides more information on women and heart disease, the subjects of this study were not necessarily athletes. In fact, most were overweight and overfat, and many had high cholesterol and blood pressure, and were smokers.
The “new female” formula–206 minus 88 percent of age – provides only a general estimate of the peak heart rate a healthy woman should attain during exercise stress tests, and not during regular exercise. The study does not compare or highlight other factors that may be as or more useful in determining increased risk of heart disease, including waist circumference, blood pressure and family/personal health history, and heart-rate variability (read my article on this important topichere).
When it comes to exercise, like everything else, individuality is most important in women and men. If your goal is to burn more body fat, get thinner and more healthy or train to run a 10K or marathon (or even if you’re a professional endurance athlete), this new formula won’t help, unless you’re going in for a stress test.
Let’s look at both maximum and exercise heart rate numbers, and ways to determine them for your particular needs. The following section is taken from my new book, “The Big Book of Endurance Training and Racing,” which will be in stores by September.
Exercise Heart Rate
There are two main formulas that are associated with endurance exercise, the type most people perform. These include the 180-Formula, which I developed in the early 1980s, and the traditional 220-Formula which is older and used much less today.
Using the traditional 220-formula, an individual would determine the training heart rate by two steps:
• The first is subtracting their age from 220 to get their maximum heart rate. In reality, most athletes who obtain their maximum heart rate by pushing themselves to exhaustion will find it is probably not 220 minus their age. About a third will find their maximum is above this heart rate, a third will be below, and only a third may be close to what they’ve calculated. These inaccuracies are often significant.
• The second step uses this so-called maximum heart rate, which is then multiplied by 65, 70, 75, 80, or 85 percent. The percentage most athletes choose is the higher option since most feel the need to train with more intensity to obtain benefits. This results in a relatively high training heart rate. Moreover, the range between 65 and 85 percent is so wide that most athletes who work out without thought of heart rate or intensity will fall into this range.
Since everyone is unique, the 220 Formula is not accurate as it relies on an estimated maximum heart rate, which is not very accurate and a wide range of workout intensities. In addition, this formula fails to take fitness, health, and aging into account.
What is Age?
There are two ways to define age. Chronological age is measured by calendar years, but this may not be a good reflection of fitness and health. We all know athletes who appear much younger—or older—than their chronological age. Some maintain better levels of physical, chemical, and mental function throughout life, reflecting a truer physiological age, while others who are the same chronological age do not. We can evaluate these differences by measuring heart and muscle function, blood sugar, and hormone levels, and by performing other clinical tests. An appropriate questionnaire that asks about fitness and health history is also very useful to assess physiological age, and would better represent “age” in a more accurate calculation, such as the 180-Formula.
This approach is more individual since it incorporates the person’s level of fitness and health, and it does not consider maximum heart rate. The MAF 180 Formula provides two important benefits. First, it trains your body to burn more stored fat for energy (we normally burn varying amounts of both sugar and fat). This is important for overall health. Second, it enables you to run, bike or perform other activities faster over time (weeks and months), all while remaining at the same training heart rate. This is important if you’re a competitive athlete.
To find your maximum aerobic training heart rate, there are two important steps. First, subtract your age from 180. Next, find the best category for your present state of fitness and health, and make the appropriate adjustments:
1. Subtract your age from 180.
2. Modify this number by selecting among the following categories the one that best matches your fitness and health profile:
a. If you have or are recovering from a major illness (heart disease, any operation or hospital stay, etc.) or are on any regular medication, subtract an additional 10.
b. If you are injured, have regressed in training or competition, get more than two colds or bouts of flu per year, have allergies or asthma, or if you have been inconsistent or are just getting back into training, subtract an additional 5.
c. If you have been training consistently (at least four times weekly) for up to two years without any of the problems just mentioned, keep the number (180–age) the same.
d. If you have been training for more than two years without any of the problems listed above, and have made progress in competition without injury, add 5.
For example, if you are thirty years old and fit into category (b), you get the following:
180–30=150. Then 150–5=145 beats per minute (bpm).
In this example, 145 will be the highest heart rate for all training. This is highly aerobic, allowing you to most efficiently build an aerobic base. Training above this heart rate rapidly incorporates anaerobic function, exemplified by a shift to burning more sugar and less fat for fuel.
Two situations may be exceptions to the above calculations:
- The 180 Formula may need to be further individualized for people over the age of sixty-five. For some of these athletes, up to 10 beats may have to be added for those in category (d) in the 180 Formula, and depending on individual levels of fitness and health. This does not mean 10 should automatically be added, but that an honest self-assessment is important.
- For athletes sixteen years of age and under, the formula is not applicable; rather, a heart rate of 165 may be best.
If it is difficult to decide which of two groups best fits you, choose the group or outcome that results in the lower heart rate. If in doubt, further individualization with the help of a healthcare practitioner or other specialist familiar with your circumstance and knowledgeable in endurance sports may be necessary.
Once a maximum aerobic heart rate is found, a training range from this heart rate to 10 beats below could be used. So if your maximum aerobic heart rate is determined to be 155, the aerobic training zone would be 145 to 155. However, the more training at 155, the quicker benefits will be realized.
Maximum Heart Rate
Take a group of fit individuals of the same age, gender, and ability, and the maximum heart rates will vary considerably. How is this best determined? There are two ways to find your maximum heart rate. One is by trial, and the other by formula.
The best approach for any fit individual is by trial. Your maximum heart rate for specific activities can be determined following about three to four minutes of maximum (all-out) training, with running being the most effective way to bring the heart rate to the highest level. This is not recommended for those who are not well trained.
A general formula often used for determining your maximum heart rate—for healthy adult male and female athletes not on medication—is 208 minus 70 percent of age (subtract the result of 0.7 times your age from 208). Whether this will be replaced by the new research formula when women are tested is yet to be determined. But even using this or other formulas, those who are fit usually won’t find the same maximum heart rate as performing a trial. In most cases, actual maximum heart rates are higher.
Maximum heart rates vary between different types of activities. Running would produce the highest maximum rate compared to cycling or swimming in the same person. This is due to the increased amount of muscle mass associated with more gravitational stress that accompanies running compared to other activities.
Maximum heart rate may also vary due to a person’s training and stress levels (level of rest), nutritional status (such as hydration), weather (high vs. low humidity), and other factors. This can produce a wide variety of maximum heart rates; a group of 40-year old athletes can have a normal range of maximum heart rates between 160 to 200 beats per minute.
The maximum heart rate can also change with training. In particular, the maximum rate can decrease with successful aerobic training. This is due to increased efficiency of the heart, changes in blood volume and other factors. It’s also been shown that maximum heart rate can increase during periods of less or training. These variations can be about 5%.
How is maximum heart rate useful for those who exercise? While many athletes talk about their levels, often believing that higher is better, which is not necessarily true, there are at least two uses of maximum heart rate.
- I recommend using a percent of maximum heart rate to obtain a general guideline for training during anaerobic work. This is the training intensity that produces maximum benefits, and rising above this heart rate during an anaerobic workout may produce little or no additional benefits while adding potentially harmful stress. This percentage is 90% of your maximum heart rate. It’s useful during interval training, hill repeats and any anaerobic workout except weight lifting (where monitoring the heart rate is much less important).
- Another use of maximum heart rate is to compare your rate as determined in training to a general formula that predicts max heart rate. Athletes who don’t come close to their predicted maximum heart rate, compared to the actual one determined during a hard workout, could have a problem with the nervous system (specifically, the autonomic nervous system) which controls the heart, blood vessels and other areas, and can even indicate an increased risk of sudden death (these cases are sometimes associated with very low maximum heart rates).
As researchers continue to find better ways to predict heart and other diseases, each of us bears the ultimate responsibility of taking care of ourselves to avoid disease and live life to its potential. This is accomplished through improvements both in fitness, such as with regular exercise that improves fat burning, and in health which includes diet, nutrition and stress control. The media play a big role in educating the public, but not when they jump to hasty conclusions.