RPE: Rating of Perceived Exertion

The lifting version of RPE ties each score to reps in reserve (RIR): how many more good reps you could have done when you stopped the set. It was published by Zourdos and colleagues in 2016 and is the scale most lifting apps and coaches use.

• Read a prescription like this: “3 × 8 @ RPE 8” means three sets of eight reps with a weight that leaves about two reps in the tank on each set.
• Most working sets land around RPE 7–9 (1–3 reps in reserve). That is hard enough to build strength and muscle while keeping form and recovery in check.
• Warm-up sets are RPE 5 or below.
• Let the weight move with the day. RPE is a form of autoregulation: on a good day, RPE 8 may be heavier than last week; on a bad day, lighter. The effort stays the same.
• Rate the set straight after you finish it, and base the score on the reps you could have done with the same form, not on how out of breath you are.

It gets better with practice. In the 2016 study that introduced the lifting scale, experienced squatters rated their efforts differently from novices at the same loads, and a 2017 study found that most people underestimate how many reps they have left, with accuracy improving as they gain experience.

If you are new to lifting, treat your RPE as a rough guide: aim a little lower (RPE 7, about 3 reps in reserve) and now and then check yourself with a set taken to the last good rep on a safe exercise, such as a machine.

For endurance exercise, RPE usually means one of Gunnar Borg’s scales: the original 6–20 scale (6 is no exertion at all, 20 is maximal) or the 0–10 category-ratio (CR10) scale. These rate whole-body effort, including breathing, rather than reps left in a set, so a lifting RPE 8 and a running RPE 8 are not the same thing.