Which one is better for beginners?

RIR is often better for beginners because counting 'reps left' is more concrete than judging an abstract feeling scale. Asking 'Could I have done 2 more?' is a yes/no question.

Should I train to RPE 10 (Failure)?

Not always. Training to failure accumulates high fatigue. Most gains are made in the RPE 7-9 range. Save RPE 10 for isolation exercises or the last week of a training block.

RPE vs RIR: Which Should You Use?

Training autoregulation works best when you can target effort precisely. Two common scales are RPE (Rate of Perceived Exertion) and RIR (Reps in Reserve).

They describe the same thing in different directions: how close a set is to failure.

Simple conversion Table

RPE	RIR (Reps Left)	Feeling
10	0	Max effort. No more reps possible.
9.5	0-1	Maybe 1 rep, but form would break down.
9	1	Could definitely do 1 more rep.
8	2	Could do 2 more reps.
7	3	Bar speed is fast, but weight feels heavy.
6	4+	Warm-up weight.

Use this table as a communication layer: if your coach writes RPE 8, think “about 2 reps in reserve.”

When to use which

Choose RIR (Reps in Reserve) if:

You are a Beginner/Intermediate. Counting concrete reps is easier than guessing abstract feelings.
You are doing Hypertrophy work (sets of 8-15). "2 reps left" is a clear target.

Choose RPE (Rated Perceived Exertion) if:

You are an Advanced Lifter. You know exactly what a "heavy single" feels like.
You are doing Strength work (sets of 1-5). RPE allows for finer decimals (e.g., RPE 8.5) that RIR misses.

Coaching cues to judge effort

How do you know if it was really RPE 9?

Bar speed slows significantly on the last rep.
Form starts to drift (knees cave slightly, back rounds) but doesn't break.
Involuntary speed loss. You define success by pushing as hard as possible, but the bar moves slow.

How Bion uses both

Plans prescribe effort as RPE or RIR depending on lift and goal.
Your past performance tunes the target next session.
If readiness is low, Bion nudges effort down and volume up (or vice versa).

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RPE (Rate of Perceived Exertion) measures how close to failure a set feels on a 1-10 scale (where 10 is max). RIR (Reps in Reserve) counts how many actual reps you could have done when you stopped. RPE 9 = 1 RIR.