Measuring Intensity

We know that high intensity/vigorous exercise is a great way to build muscle, improve insulin sensitivity, and improve blood glucose regulation alongside many other health benefits. But how do we accurately measure the intensity of our exercise? How do you know when we are exercising ‘hard’ enough?

Rate of perceived exertion (RPE) 

The first widely accepted measure is the Rate of Perceived Exertion (RPE). This is a self-reported measure of intensity on a scale of 1 - 10:

1. At rest

2. Very easy

3. Moderate

4. More purposeful

5. Starting to become warm

6. Challenging but sustainable for 20mins or more

7. Very challenging

8. Very tough

9. Almost flat out

10. Absolute limit, only sustainable for a few seconds

You simply measure how you're feeling during the activity against the RPE and choose a number. Using this scale, any time spent during an activity at an RPE of 7 or more would be considered ‘high intensity/vigorous’. This can be applied to any type of exercise.

Talk test (TT) 

Another measure to utilise while you are exercising is the Talk Test (TT). This test follows a simple rule: the harder it is to talk, the harder you're working:

Light exercise/rest: you can talk comfortably, with no limitations.

Moderate exercise: you're starting to feel more breathless, but are still able to hold a conversation.

Intensive exercise: you're breathing hard and fast and find it difficult to hold a conversation. You may only be able to manage one word between breaths, or no words at all.

You can combine these two measures to get a greater understanding of how you’re feeling as shown below:

Rate of Perceived Exertion (RPE) & The Talk Test

1. At rest

2. Very easy

3. Moderate – can talk easily

4. More purposeful

5. Starting to become warm – sporadic conversation

6. Challenging but sustainable for 20min +

7. Very challenging – short sentences only

8. Very tough – one word answers

9. Almost flat out

10. Absolute limit, only sustainable for a few seconds – unable to speak

Heart rate (HR) 

If you fancy doing some math, you can also assess the intensity of a workout using your heart rate (HR). This method is quite in-depth, and not completely necessary as the subjective measures above should provide you with all you need. However, for those of you keen to gauge a more comprehensive understanding of your workouts, you can start by calculating the following:

Resting Heart Rate (RHR): locate your pulse and count how many beats there are in one minute

Maximum Heart Rate (MHR): 220 - your age

Heart Rate Reserve (HRR): MHR - RHR

High-intensity exercise is considered to be between 70%-85% of your MHR, so to calculate your high-intensity zone:

Multiply your HRR by 0.7 then add your RHR

Multiply your HRR by 0.85 then add your RHR

Example:

28 year-old runner

RHR = 50

MHR = 192

HRR = 142

Vigorous intensity threshold = 149bm - 170bpm

The runner completes a 4km run with an average HR of 167, which is very close to the top range of their vigorous activity threshold, therefore indicating the workout they completed was at very high intensity.

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