Using Heart Rate Reserve to Determine Cardio Intensity

When it comes to weight training, figuring out one’s intensity is pretty simple – just add weight; the more weight, the higher the intensity. However, cardio exercise seems like a nebulous idea between walking, jogging, and running with no official distinctions between intensities; or, at least it may feel that way. In this article, I will explain how to determine intensity in training, why one method is better than others, and why intensity matters. So, now that I’ve put enough words in the introduction, let’s get to the information.

What do I need?
You need – nothing. Sure, it would be extremely helpful to have a heart rate monitor, but it isn’t necessary.

Heart Rate Reserve for Intensity
Let us cut the chase – the most effective way of figuring out your intensity is using the heart rate reserve (HRR) method. This method allows us to give an adjusted system for finding intensity that can be verified easily with a heart rate monitor. It should go without saying that the HRR method is based on heart rate. Heart rate is a response method of exercise programming, which is advantageous as it can be verified regularly, at any point during exercise.

Typically, aerobic exercise is done within a range of intensity – for example, people do not run at exactly 67% intensity throughout, but usually aim for somewhere in a range such as 60-70% (this intensity range is dependent on health and fitness level, however, and is different person to person). So, how do we find our range? Let’s take a look.


Finding Intensity Range with HRR

Okay, so here’s the thing – we have to use math. However, luckily, this will be a one time deal, and it is really easy. First, though, we need three pieces of information.

1. Resting Heart Rate
2. Maximum Heart Rate
3. Intensity Percentage

1. Resting Heart Rate
Simply, put your finger on your carotid artery (on your neck), feel the pulse, and count the number of pulses that occur in 30 seconds. Then, take that number and multiply by 2 – you now have your resting heart rate.

Example: Joseph puts his fingers on his carotid artery, counts the number of beats, and stops after 30 seconds. He got a number of 31 (this number could be considerably different for you). He would then multiply 31 by 2 to give him his resting heart beat at rest – 62 beats per minute (BPM).

2. Maximum Heart Rate
There are a few ways of going about this – the simplest being to use a tiny equation. The equation reads:

 220 – Age

Example: Joseph is 30 years old, so he will subtract 30 from 220 for a maximum heart rate of 190 BPM.

However, this method can be misleading. The advantage is that it is extremely simple to use and is accurate enough for normal individuals, but if you are taking medications that impact your heart rate or you are extremely fit, your actual heart rate could be much lower or much higher than the predicted one offered by the equation above. So, the most accurate way is, if you are able, to sprint all out, and get your heart rate blasting through your chest. Then, immediately record it the exact same way you would for resting heart rate (fingers on carotid, count beats for 30 seconds, etc…). Otherwise, in an instance where you are not able to sprint, use a treadmill and increase the grade enough to have you desperate for breath, legs burning.

3. Intensity Percentages
Simply know the percentage you would like to exercise. These will be highly dependent on your goals, but it is advisable to pick a range, allowing flexibility.

Example: Joseph would like to get the most out of his exercise by increasing his fitness level while also becoming healthier. As a result, he chooses an intensity range of 60 – 70%.

Now that we have these three pieces of information, we can plug it into this equation:


You will need to do this twice, one for your lowest desired intensity and one for your highest desired intensity.

Example: Joseph has all of his information. He has a maximum heart rate of 190 BPM according to the prediction model; he has a resting heart rate of 62 BPM, as well, and he would like to train somewhere between 60 – 70%. So, using this information, we will use the HRR equation twice to determine the heart rate at each intensity percentage.

Now that Joseph has his heart rate range he simply needs to run with enough intensity to stay within 139 and 152 beats per minute (60 and 70% intensity, respectively). This is where a heart rate monitor is a fantastic tool as it offers feedback on the go.

Why Heart Rate Reserve?
I briefly touched on this from an independent perspective, but comparative to other methods of determining aerobic (cardio) exercise heart rate reserve has noticeable advantages. Other methods of measuring exercise intensity include VO2 and Heart Rate Max%, but these are both inefficient for a few reasons.

Looking at VO2, it is instrumental in finding calories used during exercise, is a more accurate measure of oxygen consumption, and works well in terms of dosing (meaning, efficient for working at a predetermined, steady state intensity in a controlled environment). However, the drawbacks are the difficulty to measure (comparative to heart rate), the need for a controlled environment for better accuracy and reliability, and its predetermine dosing limiting you to a particular intensity without change. Heart rate reserve, on the other hand, offers a simpler way of measuring intensity, the intensity is dynamic in terms of being able to change it with ease (based on your heart rate during exercise, simply taper off or increase), and is extremely useful in uncontrolled environments (running outside, rowing, biking in the mountains, etc).

On the other hand, it seems logical to be able to use an even simpler method in Heart Rate Max%, because it does use heart rate to establish intensity. This method would simply determine maximum heart rate and then use a percentage off of that max.

So, simplicity is there and the use of heart rate is there, but in the lower levels of intensity, the intensity is underestimated. Here is an example to demonstrate that:

Taylor has a perfectly normal resting heart rate of 70 beats per minute. Taylor is 40 years old, so her maximum heart rate is, using the estimation formula (220 – age), 180 BPM. She is rather unfit and decides to start off at a range of 30-40% intensity. Here are her calculations based on HRmax%:

Remember that her resting heart rate is 70 BPM.

See the issue?
Taylor would have to workout at an intensity below resting levels.
While both of the alternative methods have applications, they are not suitable for determining exercise intensity in variable environments (outside, in the heat, cold, different terrain, activity, etc.) like heart rate reserve (HRR).


Bottom line, heart rate reserve is the best way to determine aerobic exercise intensity, because it is a response mechanism to a stimulus (being given feedback via the heart rate monitor on the tax of exercise) and can be interpreted and used to determine intensity in a variety of settings (jogging, walking, hot day, heavy incline, etc.). Heart rate reserve offers an excellent system to determine intensity for increasing performance, exercising safely, and keeping you conscious of the tax on your body.

Writer: Nicolas Verhoeven

"CLICK" for Most Recent