RPE and RIR: How to Train at the Right Intensity

How hard should you train? "Go to failure" says one camp. "Leave reps in the tank" says another. Percentage-based programs prescribe exact weights that may or may not match your capacity on any given day.

The solution: autoregulation. Training systems like RPE (Rate of Perceived Exertion) and RIR (Reps in Reserve) let you adjust intensity based on how you actually feel — not arbitrary numbers.

Here's how to use these tools effectively.

What Is RPE?

RPE stands for Rate of Perceived Exertion. It's a subjective scale measuring how difficult a set feels, typically from 1-10.

The modern RPE scale for lifting (adapted from Borg's original scale) looks like this:

Most effective training happens between RPE 7-9. Below 7 is warm-up territory; RPE 10 is true failure.

What Is RIR?

RIR stands for Reps in Reserve — how many more reps you could have done after stopping a set.

RIR is essentially the inverse of RPE:

• RPE 10 = 0 RIR (failure)
• RPE 9 = 1 RIR
• RPE 8 = 2 RIR
• RPE 7 = 3 RIR

Some people find RIR more intuitive because it directly answers: "How many reps did you leave in the tank?"

Iridium uses RIR to track your training intensity — log how many reps you had left, and the app adjusts future weight recommendations accordingly. If you consistently leave 3+ reps in reserve, it suggests increasing weight. If you're grinding at 0 RIR every set, it might suggest backing off.

Why Autoregulation Works

Daily Performance Varies

Your strength fluctuates based on:

• Sleep quality
• Nutrition timing
• Life stress
• Accumulated fatigue
• Time of day
• Countless other factors

A percentage-based program says "Squat 315 for 5 today." But what if you slept poorly, skipped breakfast, and had a stressful morning? 315 might be RPE 10 today when it was RPE 8 last week.

Autoregulation accounts for this. You work to your actual capacity, not a fixed number.

Optimal Training Zone

Research by Grgic et al., 2022 examined proximity to failure and found that training within 0-4 reps of failure (RPE 6-10) produced similar hypertrophy, with training closer to failure showing slight advantages.

The key insight: you don't need to hit failure every set, but you need to get close enough. RPE 7-9 hits this sweet spot — challenging enough to stimulate adaptation, not so hard that recovery is compromised.

Fatigue Management

Constantly training at RPE 10 accumulates excessive fatigue. Strategic use of RPE 7-8 work allows volume accumulation without burning out.

Advanced periodization alternates between higher RPE weeks (intensity focus) and lower RPE weeks (volume or recovery focus).

How to Gauge RPE Accurately

The Learning Curve

RPE is a skill. Beginners typically underestimate or overestimate how many reps they have left. Accuracy improves with experience.

Calibration tips:

• Occasionally take sets to actual failure to understand what RPE 10 feels like
• Record videos to assess bar speed — slow, grinding reps indicate high RPE
• Compare your RPE ratings to actual rep performance over time

Bar Speed as a Guide

Bar speed correlates with RPE:

• Fast, explosive: RPE 6-7
• Controlled, some slowing: RPE 7-8
• Noticeably slowing: RPE 8-9
• Grinding, very slow: RPE 9-10
• Stops or fails: RPE 10+

When the bar starts moving slowly on compounds, you're approaching RPE 9+.

Exercise-Specific Considerations

RPE feels different across exercises:

• Squats/Deadlifts: High systemic fatigue, cardiovascular demand affects perception
• Bench Press: More localized fatigue, easier to gauge reps remaining
• Isolation work: Higher reps make RIR harder to estimate accurately

You might rate isolation exercises 1-2 points higher than they actually are. This improves with practice.

Programming With RPE

Prescribing Intensity

Instead of fixed percentages, prescribe RPE targets:

Example:

• Week 1: Work up to RPE 7 for 5 reps
• Week 2: Work up to RPE 8 for 5 reps
• Week 3: Work up to RPE 9 for 5 reps
• Week 4: Deload, RPE 6 for 5 reps

This allows the weight to find its appropriate level each day.

Combining With Percentage Work

You can use RPE as a modifier to percentage-based training:

Example: "Squat 80% for 3 sets of 5 @ RPE 8"

If 80% feels harder than RPE 8, reduce the weight. If it feels easier, you could add weight — or simply note that you're having a good day.

Progression Models

Top Set + Back-offs:

1. Work up to a top set at target RPE (e.g., 5 reps @ RPE 8)
2. Reduce weight 5-10% and do 2-3 back-off sets at the same reps

RPE Ranges:

• Prescribe RPE 7-8 for volume work
• Prescribe RPE 8-9 for intensity work
• Prescribe RPE 9-10 for peaking/testing

Sample Week Using RPE

Iridium autoregulates based on your logged RIR — tell the app how many reps you had left, and it adjusts future sessions accordingly. Over time, the AI learns your recovery patterns and suggests appropriate intensities for each training day.

Common RPE Mistakes

Mistake 1: Everything Is RPE 10

Beginners often rate every challenging set as RPE 10. True failure means you physically could not complete another rep with acceptable form. Most "hard" sets are actually RPE 8-9.

Mistake 2: Ignoring RPE Data

If you consistently hit RPE 9+ on programmed RPE 7-8 work, your weights are too heavy. Adjust accordingly.

Mistake 3: Not Calibrating

Without occasionally testing true failure, you don't know what RPE 10 actually is. Periodic calibration keeps your ratings accurate.

Mistake 4: Inconsistent Standards

Some days you rate a grind as RPE 8; other days, a smooth set is RPE 9. Develop consistent internal standards through practice.

Mistake 5: Overthinking

RPE is a practical tool, not an exact science. Being within 0.5-1 RPE point is accurate enough. Don't stress about the difference between RPE 7.5 and RPE 8.

RPE for Different Training Phases

Hypertrophy Phase

• Most work at RPE 7-8
• Higher volume, moderate intensity
• Some sets to RPE 9, minimal RPE 10

Strength Phase

• More work at RPE 8-9
• Lower volume, higher intensity
• Occasional RPE 9.5-10 singles or doubles

Peaking Phase

• Strategic RPE 9-10 work
• Very low volume
• Building to competition/test attempts

Deload Phase

• All work at RPE 6-7 or below
• Same movements, much lighter feel
• Recovery priority

The Bottom Line

RPE and RIR give you a language for training intensity that adapts to your daily capacity. Instead of rigid numbers that may not match your actual strength on any given day, you work to appropriate effort levels.

The key principles:

• Most training: RPE 7-9 (1-3 RIR)
• Volume work: RPE 7-8
• Intensity work: RPE 8-9
• Testing/peaking: RPE 9-10
• Recovery: RPE 6-7 or below

Learn to gauge your RPE accurately, program with intention, and let autoregulation optimize your training day-to-day. The weight on the bar matters less than the effort you put into moving it.

Autoregulate with Iridium

Iridium tracks your RIR on every set and uses this data to autoregulate your training. The AI learns your patterns — when you consistently have more reps in reserve, it suggests increasing weight. When you're grinding every set, it recommends backing off. Smart training that adapts to you, not arbitrary percentages. image: "/blog/rpe-rir-training-guide-hero.png"