Using the Perceived Exertion Scale to Measure Workout Intensity

When exercising, it's important to monitor your intensity to make sure you're working at a pace that is challenging enough to help you reach your goals—but not so hard that you lose form or even injure yourself. One way to do that is to use a Perceived Exertion Scale.

This measurement is often abbreviated as RPE, or rating of perceived exertion. The standard scale is the Borg Scale of Perceived Exertion, which ranges from 6 to 20, but you can also use a simplified, 0 to 10 scale. 

The Borg Scale of Perceived Exertion

Swedish researcher Gunnar Borg developed the Borg Scale of Perceived Exertion in 1982 to determine exercise intensity based on several physical cues. These cues include breathing pattern, sweat, and fatigue level. The level of exertion is then matched to a number on a 6 to 20 point scale.

The beginning of the scale is 6, where you feel no exertion; you are sitting or standing still. Level 9 is considered an easy pace, and 12 to 14 is the start of the moderate-intensity zone. This is where it feels somewhat challenging, like a brisk walk or slow jog.

At level 15 and over, you are in the vigorous-intensity zone, which is difficult, such as when you are running. Level 20 is maximum exertion and cannot be maintained for long.

The Borg scale is meant to help estimate your heart rate during activity. You can multiply your RPE by 10 to get an estimated heart rate. For instance, if your RPE is 12, then 12 x 10 = 120 beats per minute.

Since your target heart rate depends on factors such as sex and age, the ideal and maximum heart rate for you and your goals is unique. The Borg Scale assumes that you are a healthy adult.

Simplified Perceived Exertion Scale

A more simple RPE scale is the 0-10 scale. It is based on the Borg scale and uses the same concept: Perceiving the exertion that you are experiencing using physical cues.

What differs between the two scales aside from the number ranges is that the Borg RPE scale measures exertion to help determine heart rate, and the 0 to 10 scale uses the breath as an indicator. It measures from deep breathing to quicker, short breaths.

• Level 1: I'm sitting at complete rest, no exertion
• Level 2: I'm comfortable and could maintain this pace all day long
• Level 3: I'm still comfortable but am breathing a bit harder
• Level 4: I'm sweating a little but feel good and can carry on a conversation effortlessly
• Level 5: I'm just above comfortable, am sweating more, and can still talk easily
• Level 6: I can still talk but am slightly breathless
• Level 7: I can still talk, but I don't really want to, and I'm likely sweating
• Level 8: It is quite difficult to respond to your questions, and I can only keep this pace for a short time
• Level 9: It is challenging to work at this level of exertion; I can barely breathe at all and can only say a couple of words without gasping for breath
• Level 10: It is extremely difficult to work at this level of exertion, almost impossible, and I cannot talk at all

In general, for most workouts, you want to be at around Level 5 or 6. If you're doing interval training, you want your recovery to be around a 4 or 5 and your intensity blasts to be at around 8 or 9. Working at a level 10 isn't recommended for most workouts. For longer, slower workouts, keep your PE at Level 5 or lower.

Heart Rate and Perceived Exertion Levels

Measuring your heart rate is the more precise way to determine if you are in the moderate-intensity or vigorous-intensity exercise zones. But you may not always want to wear a heart rate monitor chest strap, which is the most accurate way to measure it.

Use a heart rate monitor and note how you feel at different target heart rates. Then you can draw a correlation with the RPE scale and leave the monitor behind. Occasional workouts with the heart rate monitor will help keep you on track.

The grip heart rate sensors on cardio machines and heart rate sensors on wearables like the Fitbit and the Apple Watch are less accurate than a chest strap heart rate monitor.

But you can also see how they compare to your RPE and use them as a check. By calibrating your RPE to your heart rate, you won't have to rely on a device to know when to speed up, slow down, or increase incline or resistance.