Knowing your heart rate, measured in BPM, is useful for monitoring how hard your body is truly working and calculating things like calories burned and how many of those calories came from fat. You can use an electronic gadget like a HRM (heart rate monitor) to determine your heart rate, or you can use the age-old method of pressing your fingers to your jugular or the back of your wrist, counting the beats in ten seconds, and then multiplying by six.
Metabolic testing is the most accurate way to determine what your BPM should be at certain points during your workout, but you can also calculating your target heart rate with a formula called the "heart rate reserve" method. Here’s how:
1. Determine your maximum heart rate (MHR) by subtracting your age from 220.
2. Subtract your resting heart rate (it's best to take this when you first wake up in the morning, using the method described above) from your maximum heart rate to find your heart rate reserve (HRR).
3. Multiply your HRR by the percentage of your MHR at which you wish to train (60 to 85 percent is the usual range for people looking to increase fitness and health).
4. Add your resting heart rate back to that result to get your target rate.