by Jodi Nettleton

Published August 14, 2013

Exercise Intensity?

The previous blog indicated the amount of physical activity that is recommended for adults between the ages of 18-64 years according to the Centres for Disease Control and Prevention (CDC). The amount of spent in physical activity was based on the exercise intensity that is being performed.

Well, what is exercise intensity?

The World Health Organization (WHO) describes intensity as “the rate at which the activity is being performed or the magnitude of effort required to perform an activity or exercise”. In other words, how hard a person has to work to perform an activity or a specific exercise.

There are many ways to measure intensity, however we will only focus on two that we believe is easiest to measure for the general population. Other methods are generally performed in a laboratory with trained professionals. The two I will focus on may be done on your own with little to no extra gadgets required.

1. Heart Rate:

Heart rate is the number of heartbeats per unit of time – in this case, per minute.

To monitor intensity, one must first determine the maximum amount of heartbeats they can sustain per minute. Sounds intimidating, right?

Well, there is a simple and validated equation that requires nothing else than simple math to determine this value. No exercise required figuring this out.

The equation:

220 – age = Maximum heart rate (HRmax)

For example: if you are 35 years old, your HRmax would be (220 – 35) = 185

According to the CDC, moderate physical activity is within the range of 50% to 70% of your HRmax.

To calculate the lower end of this range:

50% of HRmax = HRmax (which is 220 – age) x 0.5

The upper end of this range:

70% of HRmax = HRmax x 0.7

Therefore, a 35 year old individual have moderate exercise intensity between 93 – 130 beats per minute.

Vigorous intensity is considered to be within the range of 70% to 85% of HRmax.

To calculate the lower end of this range:

70% of HRmax = HRmax x 0.7

The upper end of this range:

85% of HRmax = HRmax x 0.85

Monitoring your heart rate does not require you to personally count your heartbeats while exercising – that would be too much work!! There are wonderful gadgets called heart rate monitors that will do the job for you. Generally they include a belt consisting of the monitor that wraps around your chest and a watch that will show you how hard your heart is working by recording the amount of beats per minute.

Heart rate monitors range in price, from around $30 to $300. They may be found at most running and sport stores.

2. Rating of Perceived Exertion (RPE) Scale:

 The RPE scale is a subjective measure of exercise intensity. Originally created by Gunnar Borg in the 1980’s, intensity was measure on a scale of 6 – 20, based on inferred heart rates that would correspond. For example, a rating of 12 on the scale would represent a heart rate of 120. It has been modified to a scale of 1 – 10, that many people may find conceptually easier, with 0 = when the body is at rest and 10 = maximum heart rate.

However, I have posted the Borg scale from values 6 – 20 because this scale has had more research determining its validity, and is used primarily in the exercise physiology labs for undergraduate kinesiologystudents when performing exercise testing.

The rating of 6 corresponds to “no exertion at all” where 20 correspond to “maximal exertion”.

Rating between 11 – 12 are considered moderate intensity, where 13 and higher is considered vigorous.

The Borg Scale:

Picture 1


Centres for Disease Control and Prevention. (2011, December 1). How much physical activity do adults need? Retrieved August 10, 2013, from

Mayo Clinic. (2011, March 5). Exercise intensity: why it matters, how it’s measured. Retrieved August 12, 2013, from

McArdle, W. D., Katch, F. I. & Katch, V. L. (2010). Exercise physiology: nutrition, energy, and human performance, 7th. ed. Baltimore, MD: Lippincott Williams & Wilkins.

Public Health Agency of Canada. (2012, April 25). Physical activity tips for adults (18-64 years). Retrieved August 10, 2013, from

Scherr, J., Wolfarth, B., Christle, J. W., Pressler, A., Wagenpfeil, S. & Halle, M. (2013). Associations between Borg’s rating of perceived exertion and physiological measure of exercise intensity. European Journal of Applied Physiology, 113, 147-155.

World Health Organization. (2013). What is moderate-intensity and vigorous-intensity physical activity? Retrieved August 13, 2013 from


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