What Is RPE?

Rate of Perceived Exertion (RPE) is a subjective scale for quantifying exercise intensity. The original Borg scale runs from 6 to 20 (tracking approximate heart rate in tens). The modified Borg scale runs 0 to 10 and is more commonly used in strength training contexts.

In personal training, a 10-point RPE scale where 10 = maximal effort (couldn't do another rep) and 1 = minimal effort is the most practical format.

RPE is self-reported, meaning the client evaluates their own effort level. This subjectivity is a limitation early in the coaching relationship because clients often underreport or over-report. But it becomes a reliable and precise tool as clients develop body awareness through consistent coaching.

What Is RIR?

Reps in Reserve (RIR) is a related but more concrete autoregulation tool. It quantifies how many additional reps the client could have completed at the end of a set before reaching technical failure. An RIR of 2 means the client could have done 2 more reps. An RIR of 0 means they were at technical failure.

RIR is often more intuitive for clients than RPE because it's anchored to a concrete behavioral reference ("how many more reps could you have done?") rather than a subjective intensity rating.

The relationship between RIR and RPE is approximately:

RIR 4+ ≈ RPE 6; RIR 3 ≈ RPE 7; RIR 2 ≈ RPE 8; RIR 1 ≈ RPE 9; RIR 0 ≈ RPE 10.

Why Autoregulation Produces Better Outcomes

On a day when a client is well-rested, well-fueled, and mentally focused, percentage-based programming may leave them under-challenged. This means the load that was appropriate based on last week's performance is now below their actual capacity.

Whereas, on a day when they're sleep-deprived, stressed, or coming off a hard previous session, the same prescribed load may be beyond their recovery-adjusted capacity and increase injury risk.

Autoregulation solves both problems. On good days, the client works harder; on a hard day, the client works appropriately. Both outcomes serve long-term progress better than rigid percentage adherence.

How to Implement RPE and RIR With Clients

Start by calibrating the scale through shared experience. Have the client perform a set to near-failure and then ask: "How many more reps do you think you could have done?" This grounds their RIR sense in a real experience. Over several sessions, their self-reporting becomes increasingly calibrated.

Program using RIR targets rather than (or in addition to) specific load. For example, 3 sets of 8 reps at RIR 2 tell the client to choose a load where they could do 10 reps but stop at 8.

This ensures they're working at the right intensity for the phase goal—not under-loading because they guessed low, not over-loading because they guessed high.

Autoregulation Across Training Phases

RPE/RIR targets should shift with training phase goals:

1. Stabilization phase (NASM OPT Phase 1): RIR 3 to 5. Emphasis on movement quality, not intensity.
2. Strength endurance phase: RIR 2 to 3. Moderate intensity, higher volume.
3. Hypertrophy phase: RIR 1 to 2. Closer to failure to maximize hypertrophic stimulus.
4. Maximal strength phase: RIR 1 to 2, with some true failure sets.
5. Power phase: RPE-based approach less applicable. Power training emphasizes bar speed over subjective effort.

RPE & RIR Training: The Bottom Line for Smarter Programming

Use RPE and RIR to deliver more precise, personalized strength training that adapts to real-time performance. This approach helps clients train at the right intensity every session—driving better results with less guesswork.

RPE and RIR turn rigid programming into a responsive, autoregulated system that adjusts to daily readiness, improving strength gains, recovery, and long-term progress. For intermediate and advanced clients, this method consistently outperforms fixed percentage-based models.

Build your coaching edge with advanced programming strategies through the National Academy of Sports Medicine (NASM) Performance Enhancement Specialization (PES).