How Do I Know What Intensity to Exercise At?

What intensity you exercise at very much depends on your fitness goal as different intensities have different effects on the body. 

By understanding how different intensities affect us and their different benefits, you can tailor your training to get the most of what you need.

If you wanted to improve your race performance and run faster, your training would be made up of both cardio endurance and anaerobic training.

If you wanted to burn fat and were willing to put in lengthy, low intensity sessions, you would do a lot of fat burn extended cardio. 

If on the other hand, you wanted to burn fat but don’t have time for lengthy low intensity sessions, you would incorporate anaerobic and maximum intensities into your training also known as HIIT training – high intensity interval training.   

How Do I Monitor My Training Intensity?

Training intensities can be monitored and tracked in different ways.  A common method used is to calculate maximum heart rate and use a heart rate monitor while training.  

Heart Rate Training

The traditional method for calculating maximum heart rate is 220 – age.

Example: A 37-year-old individual training at 70% Maximum Heart Rate.  

220 – 37= 183bpm MHR 

70% MHR = 128bpm

This formula only provides an estimate MHR, it also doesn’t take into account the difference between MHR and resting heart rate (RHR), also known as heart rate reserve (HRR).

The Karvonen Formula uses the HRR to calculate training zones based on both maximum AND resting heart rate.


a 37-year old, with resting heart rate of 57 bpm

220 – 37 = 183 MHR

183 – 57 = 126 HRR

Training zones for this individual

60% 126 x 0.6 = 76 + 57 = 133bpm

70% 126 x 0.7 = 88 + 57 = 145bpm

80% 126 x 0.8 = 101 + 57 = 158bpm

90% 126 x 0.9 = 113 + 57 = 170bpm

Using the traditional 220 - age formula this same person would have a target heart rate of 128bpm, which is considerably lower than the Karvonen method which is 145bpm. The Karvonen Formula nearly always calculates a higher target heart rate than 220 age.  Neither of these methods are flawless as every individual is different.  It is best to use the above as guidelines and monitor your personal performance and tweak as appropriate.

Rate of Perceived Exertion

If you don’t have a heart rate monitor, a simple way to track your intensity is to use a Rate of Perceived Exertion.  In its simplest form, the scale measures how you feel on a scale of 1 – 10.

Although a scale like this is easy to use, it relies heavily on your self-perception and honesty of how hard you are working.

Be clear on what you want to achieve and identify the training zones that will help you achieve your goal.  A Personal Trainer can design the appropriate training programme for you, ensuring you are working in the optimum training zones for your goal.