Rate of Perceived Exertion
RPE is a 1–10 scale for how hard an exercise or session feels. RPE 2–3 is very easy and conversational. RPE 5–6 is moderate, with several clean repetitions remaining. RPE 7 is challenging but controlled, with roughly 2–3 clean repetitions remaining. RPE 8+ is hard to maximal and is not a target to chase in this system.
Reps in Reserve
RIR means Reps in Reserve: the number of clean repetitions you believe remain before technique breaks down. Two RIR means you stop while you still have about two good repetitions available.
Use both signals
Use the target effort in the program, observe how movement quality holds, and modify early if sleep, soreness, coordination, or energy makes the planned effort inappropriate.