Rate of Perceived Exertion (RPE): An Overview
Rate of Perceived Exertion (RPE): An Overview
The rate of perceived exertion (RPE) is a term used regularly in the exercise world. While a relatively simple concept, RPE can often be inaccurately reported or misused. This blog post will delve into what RPE is and its importance, two commonly-used RPE scales and the relationship between RPE and reps in reserve (RIR).
What is RPE?
RPE is a measure of how difficult something is. In the context of exercise, it is how difficult a given bout of exercise is. Often RPE is misinterpreted as a measure of how difficult you think something (exercise) should be. While this misinterpretation is understandable, it should be emphasised that RPE is a measure of how difficult you find it (in other words, your perceived exertion).
RPE can be used across all modes of exercise - whether it be aerobic, strength or power training!
RPE charts
There are two main scales used to measure RPE.
Borg Scale
The Borg scale ranges from 6-20. A rating of 6 indicates that the activity is extremely easy for you, and it can (literally) be done all day without breaking a sweat. An example of this would be sitting on the couch watching television.
On the other end, a rating of 20 indicates that the activity is that of utmost difficulty, and you could only do it for a matter of seconds. An example of this would be sprinting your absolute hardest for 100 metres.
With these two extremes in mind, it becomes easier to navigate everywhere from 7-19.
Modified Borg Scale
The ‘Modified Borg Scale’ is a revised version of the Borg scale described above and ranges from 1-10. This one is more self-explanatory, whereby a 1 indicates an activity is super easy, 10 is extremely hard, and 2-9 is everything in between. This version of the scale is more often used in resistance, or strength training, as the 1-10 values correlate nicely with 10, 20, 30… etc. % of 1-repetition maximum.
Why use RPE?
So why do we use these two scales? What is the purpose of using RPE?
Firstly, RPE is an easy and effective way of gauging exercise intensity. We can typically assess intensity of exercise with measures such as heart rate or VO2 max testing using clinically equipment. These measures are either difficult to conduct, impractical, time-consuming or too expensive to implement.
However, RPE is free and is relatively easy to use! Most importantly, it is effective at enabling everyone to exercise at an appropriate intensity independently. This is extremely important for you to be able to engage in exercise and monitor the intensity yourself!
With this in mind, it is important that RPE is used accurately and correctly. A common error that clinicians see is under-reporting of RPE. For example, rating a jog as an 11 when it is actually closer to 15. Reporting RPE accurately ensures that exercise is prescribed and performed at the right intensity level for your particular goals, whilst ensuring safety and minimising the risk of injury. To avoid under-reporting RPE, it is important to be honest with both yourself and your clinician when asked for your RPE during an activity. Don’t be shy, ask your clinician questions! Although it may be tempting to under-cut yourself and say something is easier than it actually is, in the long run, this will likely delay you from reaching your goals and put you at a higher risk of injury!
Another common misconception is that in order to see improvements in fitness you must increase your RPE. While this is highly goal-dependent, in most instances, this is not the case. Yes, over time, the load should be increased (for example, lifting 12.5kg instead of 10kg). However, because you would expect improvements in strength to offset this increased load, the RPE should actually remain the same!
What RPE should I exercise at?
There is unfortunately no simple answer to this question. There are various factors that influence at what RPE level you should be exercising at, such as:
The type of training you’re doing
Your health status
It is best to get in contact with an exercise physiologist who will be able to determine the most appropriate RPE for your goals.
The relationship between RPE and RIR
In the context of resistance training specifically, the concept of ‘repetitions in reserve’ (RIR) is also important to address.
RIR refers to the amount of repetitions that you believe you could have performed had the set continued.
For example, after completing a set of 10 repetitions of squats, if you believe you could have done 5 more, your RIR is 5. If you had 3 more in the tank, your RIR is 3, and if you had 0 left in the tank, your RIR is 0.
Great- but why is this relevant?
Well, RIR is the opposite of RPE. In theory, an RPE of 7/10 should therefore mean and RIR of 3. Similarly, a 10/10 RPE should mean an RIR of 0 (i.e. maximum exertion with nothing left to give). The next time you’re at the gym, have a think about how you feel after your sets.
If you wanted to learn more about RPE scales or where to start in terms of setting the correct exercise intensity for yourself, get in touch with our exercise physiologists at Aevum Physiotherapy today!
Brandon Coorie, Accredited Exercise Physiologist
Aevum Physiotherapy
02 8544 3231