Reps in reserve is a decision, not a feeling

Reps in reserve, or RIR, is the simplest way to talk about how hard a set was: how many more reps could you have done before form broke down. Two in reserve means you stopped two short. Zero means the next rep was not happening.

It is a good idea with a bad habit attached. Most people use it as a description after the fact, when it only pays off as a decision made before the set starts.

Why the number moves

Rate your last set honestly and you will find the estimate drifts. Late in a session, three reps in reserve feels like one. Early, with fresh legs and a bit of adrenaline, one feels like three.

That drift is not a personal failing, it is well documented, and it gets smaller with training age and with proximity to failure. Close to the limit, the body gives clearer signals. Five reps out, almost nobody is accurate.

Deciding before the set

The useful version is the reverse: you pick the target, then you pick the load that should land there.

• Two in reserve on your main lift for most working sets
• One or zero on the last set only, and only on movements that fail safely
• Three or four on anything technical, or the week you come back from a break

The point is that the load is now the variable. If the set ends at four in reserve, the load was light and you know it before the next session, not six weeks later.

What that changes in practice

You stop chasing a rep count and start chasing a distance from failure. The rep count follows. On a good day the same load gives you an extra rep at the same effort, and that is the signal you were looking for all along.

Writing it down without ceremony

RIR only works if it survives contact with a real session. One number per working set, taken in the rest period, next to the load and the reps. Nothing else.

That is the whole point of tracking: not an archive of what you did, but the one number you need in front of you when you decide the next set.