5-star Fitness

Learn How to Target Your Heart Rate During Cardio Workouts

Written By admin • 5 min read

As a running coach and for my own training, I have used various lab tests, field tests and standard formulas to determine heart rate zones for cardio training.

Why all the research?

For myself, I want to make sure that in my endurance training, I will reap the benefits of each individual training session, whether the day calls for a slow-and-steady pace, a “threshold” or “tempo” run, or killer speed intervals!  Knowing my training zones for all my training day goals keeps me in check.  Am I working hard enough?  Am I working too hard?  My heart rate zones keep my training purposeful and keep me on task.

The most accurate way to determine your heart rate training zones is to do a VO2 Max test in a lab setting.  The test can be done on treadmill or bike.  Over the years, I have administered this test for clients of all fitness levels, from the unfit individual to the elite athlete.

[Related: Sports Training]

A metabolic analyzer is attached to the individual via a facemask and hose and the individual is put through a protocol that increases in intensity over the duration of the test.  As the intensity increases, the person’s heart rate increases respectively.  The metabolic analyzer detects exactly when (the exact heart rate) the individual begins to transition from his/her aerobic to anaerobic state, referred to as one’s “anaerobic threshold”.  Once a person transitions into anaerobic metabolism, the rate of lactic acid build-up becomes too great for the person’s body to continue on for a long duration.

The closer you get to your maximum heart rate, the shorter your work effort can be before your body fails you.  From the metabolic analyzer data I collect, I use percentages of the anaerobic threshold heart rate (AT heart rate) to determine heart rate training zones for my clients.

Although the V02 Max test will give you very accurate, individualized data specific to you and your body, it is not a test the masses do for various reasons —the cost, the assumption this test is only for “athletes”, inconvenience of finding and going to a lab that administers the test, etc.

Therefore, there are other ways of determining your training zones at home and at no cost to you, such as using the Karvonen Formula.

This formula will give you your heart rate training zones, but remember, this is a standardized formula so the margin of error is definitely greater than a lab test.  However, the Karvonen Formula will give you a framework from which to base your cardio workouts—better than stabbing in the dark, guesstimating, or not monitoring your heart rate at all!

What I like about using the Karvonen Formula, versus just using a percentage of your Predicted Maximum Heart Rate, is that the Karvonen Formula takes into account your Heart Rate Reserve (HRR: the difference between your Predicted Maximum Heart Rate and Resting Heart Rate).  Two individuals of the same age can have very different zones if their Resting Heart Rates differ greatly from one another.  A more cardiovascularly fit individual will theoretically have a lower Resting Heart Rate than an unfit individual.  This difference will alter heart rate training zones, even for people of the same age.

[You might also be interested to read 5K Race Training Part I & Part II]

Follow these six simple steps to calculate your target heart rate training zones.

Step 1:  Calculate Average Resting Heart Rate

To calculate your Resting Heart Rate (RHR), take your pulse the moment you wake up, before you sit up!  Keep a watch nearby and take your pulse for 15 seconds while lying down.  Multiply that number by 4 to calculate your heart rate (beats per minute).

Example:  15 beats x 4 = 60 bpm (RHR)

NOTE:  Take your pulse over 5 consecutive days.  Then take an AVERAGE of the 5 days to determine your average RHR.

Step 2:  Calculate (Predicted) Maximum Heart Rate

220 –   ______________  = MHR
                      Your Age

Example:  220 – 40 years old = 180 MHR


Step 3:  Insert MHR and RHR into Karvonen Formula

Here is the formula:

MHR – RHR = _____________ x  %  = _____________  + RHR


For this example of a 40 year old with an average RHR of 60 wanting to train in her “aerobic zone” of 70%, the formula is as follows:

180 – 60 = 120 x 70% = 84 + 60 = 144 bpm

Step 4:  Calculate 5 Training Zones from 50% – 90%

For my example client, here are her calculations and target heart rates:

Zone 1: 180-60=          |  120 x 50%= 60 + 60 (RHR)=         |  120 bpm (50%)

Zone 2: 180-60=          |  120 x 60%= 72 + 60 (RHR)=         |  132 bpm (60%)

Zone 3: 180-60=          |  120 x 70%= 84 + 60 (RHR)=         | 144 bpm (70%)

Zone 4: 180-60=          |  120 x 80% = 96 + 60 (RHR)=        | 156 bpm (80%)

Zone 5: 180-60=          |  120 x 108%=108 + 60 (RHR)=     | 168 bpm (90%)


Step 5:  Purpose of Zones 1 -5:

Zone 1:  For recovery.  Also for beginners or people coming back to training after a long time.  Body utilizes fat for energy but you must train for long periods of time in this zone for weight loss.

Zone 2:  Body utilizes fat for energy and your heart begins to benefit from working in this zone.  This zone is good for slow, long distance.

Zone 3:  This zone is considered your “aerobic zone” and is a great target fitness zone.  Training in this zone will improve your cardio-respiratory system.

Zone 4:  This is the zone where you transition from aerobic to anaerobic training (anaerobic threshold).  Your body starts using carbohydrates as its energy source in this zone.  You will feel fatigued, you will breathe much harder and will not be able to talk while training in this zone.  The by-product of this high level of energy expenditure, lactic acid, starts building in your muscles at a faster rate than your body can clear it out.  It is beneficial to train in this zone periodically (I do one day per week), as training in this zone will actually push out when you go fully anaerobic, thus increasing your overall aerobic capacity.

Zone 5:  This is the hardest level of training and you will only be able to maintain it for a short period of time.  Short spurts of effort to get your heart rate to this zone must be followed by recovery time in Zone 1.  A type of Zone 5 workout is interval training.

Step 6:  Put The Numbers To The Test!

Go ahead!  Get training and your heart will thank you!


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Wendy is an ACE Certified Personal Trainer, NASN Licensed Sports Nutritionist and RRCA Certified Running Coach.  She has worked in the fitness industry since 2003.  She has advanced education in various specialties such as functional training, corrective exercise, and nervous system impairments.  She works with clients of all fitness and wellness levels, from individuals recovering from strokes and heart attacks to competitive athletes seeking higher levels of sports performance.  Wendy has found her home as a Fitness Trainer with Premier Fitness Camp and is inspired daily by the determination and tenacity of Premier’s clients!

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