How to Calculate Maximum Heart Rate and Training Zone Heart Rate

To get the most out of an aerobic workout, it is important to exercise at an intensity level between 60% and 85%. And how do you determine if your workout is within this intensity range? By measuring your heart rate, specifically, the number of beats per minute.

When you are working out at a 60%-85% level, your heart rate is within what is called the training zone. To calculate your training zone heart rate, you need to know three things: your maximum heart rate (MHR) which corresponds to 100% intensity, your resting heart rate (RHR) which corresponds to 0% intensity, and a special equation called the Karvonen formula.

Difficulty: Moderately Easy

Instructions

1. First, calculate your maximum heart rate, MHR, by subtracting your age in years from 220. For example, a 31 year old has a maximum heart rate of 220 - 31 = 189 beats per minute.
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   NOTE: There are 3 alternative formulas for maximum heart rate, each very similar to the one above. As yet, there is no universally accepted MHR formula, but here are the other 3 in case you are interested. (A = age in years)
   
   1st alt MHR = 205.8 − (0.685)A
   2nd alt MHR = 206.3 − (0.711)A
   3rd alt MHR = 217 − (0.85)A

2. Next, figure your resting heart rate, RHR. When you wake up in the morning, count your pulse for 15 seconds and multiply by 4 to find the beats per minute. (Alternatively, count for 20 second and multiply by 3)
   
   For our example, let's say our person has a RHR of 60 beats per minute.

3. Now, use the Karvonen formula to determine your training zone heart rate. The training zone is a range that tells you how fast your heart should be beating when you are working out at a 60%-85% intensity level. The upper end is given by the equation
   
   Upper End = (0.85)MHR + (0.15)RHR
   
   and the lower end is given by the equation
   
   Lower End = (0.60)MHR + (0.40)RHR

4. For the person in our example with MHR = 189, and RHR = 60, the upper end of the training zone heart rate is
   
   (0.85)189 + (0.15)60 = 170 bpm
   
   and the lower end is
   
   (0.60)189 + (0.40)60 = 137 bpm
   
   So when his heart rate is between 137 and 170 beats per minute during a workout, he is exercising at an intensity level of 60%-85%.

5. To find your target heart rate for an arbitrary intensity level "i" (expressed as a decimal) use this formula:
   
   (i)MHR + (1-i)RHR
   
   For instance, if the person in our example wanted to know what his heart rate would be at a 72% exercise level, he would compute
   
   (0.72)MHR + (0.28)RHR
   
   which yields
   
   (0.72)189 + (0.28)60 = 153 bpm
   
   So his heart will beat at a rate of 153 beats per minute in a 72% intense workout.