| Determining Your Maximum Predicted and Target Heart Rate |
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Target heart rate is a very common method to gauge or set the intensity of aerobic exercise. Before you can set a target heart rate you first need to know your maximum predicted heart rate(HRMax.) The most commonly used formula for determining the target heart rate uses the "220-age" formula. This method predicts a HRMax by subtracting the exerciser's age from 220. The figure derived is now multiplied by the desired percentage of intensity for exercise.As an example, a 25 year old athlete in good physical condition might desire to train at 80% of their maximum predicted heart rate. Using the formula above, their target heart rate would be 156 bpm(beats per minute.) 220 – 25 = 195 x .80 = 156 bpm Another method for determining the target heart rate takes into consideration the individual's resting heart rate. This method is the Karvonen formula. You still predict a maximum heart rate by subtracting age from 220. Next you subtract the resting heart rate to obtain the heart rate reserve. The heart rate reserve is now multiplied by the desired percentage of intensity and then added to the resting heart rate. The resting heat rate should be measured while you are relaxed, awake, and preferably lying down. I recommend measuring it when you first wake up in the morning, before even sitting up in bed. Unless of course you were suddenly awakened by a bad dream. Using the same athlete from the example above, who has a resting heart rate of 54 beats per minute, their target heart rate using the heart -rate reserve method is determined to be 166.8 or 167 beats per minute, exercising at 80% of their maximum predicted heart rate. 220 – 25 = 195 – 54 = 141 x .80 = 112.8 + 54 = 166.8 beats per minute. You'll notice that there is a difference of 12 beats per minute at the same intensity. Researchers from the University of Colorado have developed a formula that is believed to be more accurate for predicting the HRMax of an older population. The recommendation is for people over age 40 to use the following formula for predicting their maximum heart rate: 208 – (Age x .7)= HRMax As an example, we'll use a 43 three year old exerciser, choosing a target heart rate of 80% of the HRMax. HRMax = 208- (43 x .7) = 208- 30.1 = 177.9 bpm We can then multiply 177.9 by .8 and find the target heart rate is 142.32 Compared to the original 220- age formula, it is only a difference of less than 1 beat per minute. However, if you do the calculations for an 83 year old selecting an intensity of 65% of HRMax, you'll see the target heart rates have a difference of over 8 bpm, and HRMax differs by over 12 bpm. For women, the most recently developed formula for predicting the maximum heart rate is: 206 – (Age x .88)= HRMax Comparing this formula to the 220-age formula, a 52 year old woman's HRMax is 7.76 beats lower. If her target rate rate is 75%, she needs to only maintain 120 bpm using the new formula, not 126 bpm using the 220-age formula. 220-52= 168 168 bpm x 75%= 126 bpm 206 - (52 x .88) or 206 - (45.76) = 160.24 160 x 75%= 120 bpm Which method should you use? Older adults, and women who are just starting an exercise program might be better off using one of the formulas specific to their demographic. Experienced athletes should experiment between the formulas that would be appropriate for their age, and gender, or the old standard 220-age. Keep in mind that unless you have an EKG test to directly measure your maximum heart rate, the formulas above serve only as a predicted estimate. When you use your heart rate to determine or guide your exercise intensity, how you feel is very important. Some people will have a higher maximum heart rate than what the formulas predict, just as some may have a lower maximum heart rate. You can use the formulas as a guideline, but if the intensity feels to high(difficult) or low(easy) adjust accordingly.
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