Reps in reserve (RIR): how hard each set should be

Reps in reserve, or RIR, is how many more good reps you could have done when you racked the bar. Stop a set of squats at 8 when you could have ground out 10, and that set was RIR 2. It's the simplest way to say how hard a set should be, and it works for any lift, any weight and any lifter.

Why effort matters more than the number on the bar

A set of 10 at a weight you could lift 20 times does very little. The same 10 reps at a weight you could lift 11 times is a hard, productive set. What makes muscles grow and strength climb is getting reasonably close to failure, so writing a program in reps alone leaves out the part that matters. RIR fills that gap: "3 sets of 8 at RIR 2" means the same thing to a beginner and to someone who has trained for ten years.

Research backs this up. Sets taken within a few reps of failure build muscle about as well as sets taken all the way to failure, with much less fatigue. Training to failure on every set mostly adds soreness and longer recovery, not extra growth.

RIR and RPE

RPE (rating of perceived exertion) is the same idea counted the other way. The lifting version, from Zourdos and colleagues in 2016, ties each RPE to reps left in the tank:

• RPE 10 = RIR 0: nothing left, a true max effort
• RPE 9 = RIR 1: one more rep was there
• RPE 8 = RIR 2: two more reps
• RPE 7 = RIR 3: three more, the bar still moves quickly
• RPE 6 or lower = RIR 4+: a warm-up or a technique set

Use whichever feels more natural. They describe the same set.

How close to failure should you train?

• For muscle: most working sets at RIR 1 to 3. The last set of an isolation exercise can go to RIR 0.
• For strength: big lifts at RIR 1 to 3, with fewer reps. Leave grinding max reps for the occasional test.
• For beginners: RIR 2 to 4 while you learn the movement. Your first sessions are about practice, and you'll make progress anyway.
• Big compound lifts (squats, deadlifts) carry more risk and more fatigue near failure, so keep an extra rep or two in the tank. Curls and raises can go closer.

Step RIR down across a training block

A good way to use RIR is to start a block a bit easier and finish it harder: RIR 3 in the first week, then 2, then 1, then 0 in the last hard week, followed by a lighter deload week. You build momentum without piling up fatigue early, and you get a planned push at the end.

Getting better at judging it

Most people underestimate how many reps they have left, especially on higher-rep sets. A few ways to calibrate:

1. Once in a while, take the last set of a safe exercise (a machine, dumbbell curls) to true failure and compare with your guess.
2. Watch bar speed: when reps slow down noticeably, you're usually 2 to 3 reps from failure.
3. Write down your RIR right after the set, not at the end of the workout.
4. Be honest. Reporting RIR 2 when it was RIR 0 just makes your next session too heavy.

Tip: A rep only counts if it's a good rep. RIR means reps you could do with the same form, not ugly reps you could force out.

How Liftsmith uses it

Liftsmith gives every working set an RIR target from the week of your block, and lets you show it as RPE if you prefer. During rest you can tap how many reps you had left; sets that felt easier than planned nudge the next session's weight up, and sets that felt harder pull it back. Missed reps and "too hard" feedback count too, so the plan follows how you're actually lifting.