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Heart Rate Formulas

Calculating Target Heart Rates and applying them to your workout.

Lewis Fannin NSCA-CPT

Many people never pay attention to what their heart rate is when they are doing cardio, and even for some people that do, they may not fully understand what the numbers are telling them. Even though perceived exertion may be a barometer for output, this article will enable you to give specificity to your cardio workouts.

A target heart rate between 50-75% will burn more fat than if your heart is working at 80-90%, which is more for endurance training and highly conditioned athletes. There are several ways to use target heart rates with cardio workouts to improve cardiac output. Before that, you need to know your Age Predicted Maximum Heart Rate (APMHR). Use this formula:

220 minus age = age predicted maximum heart rate (APMHR)

For general health and fitness, a rate of 50-75% of APMHR three to five times per week for 20-60 minutes is widely accepted (for highly conditioned athletes looking to increase muscular endurance up to 90% of AMPHR.)

Note: According to the ACSM individuals with very low fitness levels can have a significant training effect in a 40-50% range

For a 20 year old person
220-20=200
200 times .50=100
200 times .75=150

This person will want to keep his heart rate between 100 and 150 beats per minute.

Another way to find out target heart rate is using a percentage of your heart rate reserve. The benefit to using this is that it is more specific to the individual, and it more closely relates to your VO2 max, or maximum oxygen uptake.

To figure out your heart rate reserve (HRR), take your APMHR and subtract your resting heart rate (RHR) from it. Your resting heart rate should be taken as soon as you get up in the morning.

HRR formula

APMHR minus RHR=HRR
Ex. For a 20 yr. old person with a resting heart rate of 56 beats per minute: 220 – 20 (age) = APMHR
200 – 56 (RHR) = 144 (HRR)

After you figure out your HRR then you can find out what your target heart rate (THR) should be when you’re working out. We do this with a formula called the Karvonen formula.

Karvonen Formula

THR = (HRR X exercise intensity) + RHR
Ex. 144 x desired exercise intensity + 56 (RHR)
If our 20 yr. old with a resting heart rate of 56 exercises at an intensity of 70%:
THR = (144 x .70) + 56 = 156.8
Target Heart Rate is 157 beats per minute