RPE (rate of perceived exertion)
Rate of perceived exertion — a scale that rates how hard a set was, usually from 1 to 10. In the version used in strength training the number reads as the inverse of RIR: RPE 10 is failure, RPE 9 is one rep in reserve, RPE 8 is two. It lets a coach and an athlete talk about intensity without arguing about absolute loads, which move with sleep, stress and the phase of the block.
In practice
A coach writes 4×6 @ RPE 8 and the athlete picks the load that, at six reps, leaves two in the tank. Two athletes of different strength do the same session with different weights and the same relative stimulus.
How to use it in a plan
Set a target RPE per exercise and per week, and raise it through the block (say from 7 to 9) instead of fixing percentages. For accessory work a higher RPE is safe; on heavy compounds, leaving a margin protects technique and recovery.
FAQ
Are RPE and RIR the same thing?
They are two readings of the same effort: RPE 10 = RIR 0, RPE 9 = RIR 1, and so on. RPE is the scale; RIR is the count behind it.
Does it work for beginners?
With care. People with little experience tend to underrate the effort; prescribing reps and load is better at first, with RPE introduced once the estimate settles.