How to Calculate Your Target Heart Rate

It is common knowledge that monitoring your heart rate is a good way to measure the demand and intensity of cardiovascular exercise, such as walking, biking, or swimming. You can buy heart rate monitors in a wide range of prices and features or simply check your pulse to accomplish this task, but there is still the issue of how to calculate your target heart rate.

Your target heart rate is essentially the heart rate or heart rate range where you will maximize the specific benefits you want from a workout. Figuring out your target heart rate is most useful for continuous aerobic workouts where you maintain a fairly steady pace.

Other forms of exercise, such as lifting weights, repeated sprinting, interval training, and most sports have frequent fluctuations in heart rate, so the concept of a target heart rate does not really apply, or at least not in the same way. Therefore, the purpose of this article is to explain how to calculate your target heart rate as it relates to constant intensity exercise.

There is more than one approach to calculate your target heart rate. The most common method starts by finding your maximal heart rate by taking 220 and subtracting your age. Then you simply multiply that number by the percentage of your heart rate that you want to train at.

For example, I am 36, so I would take 220-36 to find my maximal heart rate of 184. As a side note, the 220 - your age equation is just an estimate and it can vary significantly by individual or age, but it is almost universally used due to its simplicity. If I want my target heart rate to be at 75% of maximum, I multiply 184 by .75 (for 75%). In this example my target heart rate would be 138 beats per minute.

This method is relatively simple to use, but it has a major flaw, in that it does not take individual differences in fitness into account. Fortunately there is a better method to use and it only requires a little more work. The improved way to calculate your target heart rate uses the Karvonen formula, which is similar, except it uses one additional variable: your resting heart rate.

People can have very different resting heart rates, sometimes varying by 30 to 40 beats per minute or more and people in better shape generally have lower resting heart rates. Since there are large differences in resting heart rates, it only makes sense that the target heart rate should take this information into account and this is what the Karvonen formula is designed to do.

However, before using the formula, you need to figure out your resting heart rate. The easiest way to find your resting heart rate is to take your pulse first thing in the morning before you even get out of bed. Anything you do can cause an increase in your resting heart rate, so just try to stay still and relax when you wake up.

All you need is a stopwatch or anything to keep track of seconds, so ideally you should have this near you before you go to bed. A common strategy is to find the pulse in your neck using two fingers (not your thumb) and count the number of beats in 15 seconds. Then multiply that number by 4 to get your resting heart rate. You can also just count the beats for the full 60 seconds and that number is your resting heart rate.

Now you can use the Karvonen formula, again starting by taking 220 and subtracting your age to get your predicted maximal heart rate. Then take this number and subtract your resting heart rate. This new number is referred to as your heart rate reserve. In my case, my resting heart rate is about 45, so I take 220 - 36 to get 184 (max heart rate), then subtract 45 (resting heart rate) to get 139 (heart rate reserve).

If I want to train at 75% I multiply .75 times my heart rate reserve, not my maximal heart rate. For me that would be .75 * 139 = 104.25. Now the last step is to add that number (104) to my resting heart rate (45) to get my target heart rate of 149. Therefore, if I want to do a cardiovascular workout at 75% intensity, I should keep my heart rate around 149 beats per minute.

When using the first equation, my target heart rate at 75% intensity was 138 or 11 beats per minute lower, which is a significant difference. Whenever you use the Karvonen formula your target heart rate will be higher and the higher your resting heart rate, the larger the difference between the two equations. This is important, because the more basic equation can underestimate your target heart rate, resulting in inferior training improvements, especially at low intensities.

On the other hand, the Karvonen formula provides some high target heart rates, especially for people who have high resting heart rates. People just beginning an exercise program may be tempted to jump right in and start training using higher intensities, but their body may not be prepared for that type of training. When beginning, it is better to start with a lower intensity (50-60%) and see how your body responds before increasing the intensity to higher levels.

Another thing to keep in mind is both equations use 220 - your age to find your maximum heart rate, so you are really just dealing with an estimate either way. However, I still prefer the Karvonen formula for calculating target heart rates, because I believe it is more appropriate for the majority of people, especially those with significant exercise experience.

My next comment may seem strange after dedicating this much text to explaining how to calculate your target heart rate, but I believe the whole concept of a target heart rate is often overemphasized. It is without question a necessity for many athletes, but the average person training to lose some fat, get in shape, or improve their quality of life, almost doesn't even have to know their target heart rate.

I would argue that instead of focusing so much on exercising at a specific heart rate, it is more important to have an appropriately designed workout program. In other words, as long as you perform exercises designed to improve the attributes you want to improve (strength, endurance, speed, etc.) and the exercises challenge your body in the correct ways, then you will make progress.

If you have more specific goals or are training to improve athletic performance, especially involving cardiovascular endurance, then training at your target heart rate may be an important part of your workouts. Just remember to keep everything in perspective and try not to become obsessed with one specific number, because there are many different factors that affect the overall success of a training program.

Reference:

1. Arnheim, D.D. and Prentice, W.E. Principles of Athletic Training, St. Louis, Missouri: Mosby-Year Book, 1993.

Additional source:

14 years of experience and education in health and fitness