RIRReps in Reserve

Reps in reserve is how many more reps you could have completed at the end of a set before reaching failure. Stopping at 2 RIR means two were left in the tank. It is the mirror image of RPE, where 0 RIR corresponds to RPE 10.

It matters because proximity to failure is one of the main variables deciding whether a set counts. Motor units are recruited in order of size, so the largest and most trainable ones only join in as the set gets genuinely hard. Sets stopped well short cost time and fatigue and contribute little.

It also matters that you need not go all the way. Training consistently to absolute failure adds fatigue disproportionately, degrades the quality of subsequent sets and makes sessions harder to recover from, without reliably adding growth. Most hypertrophy work sits well at 0 to 3 RIR.

Estimating it accurately is a learned skill and beginners are consistently poor at it, usually leaving more in reserve than they think. Occasionally taking an isolation exercise to true failure and comparing the result with your prediction is the cheapest way to calibrate.

Exercise choice changes how safe the judgement is. Going close to failure on a leg extension is unremarkable; doing it on a heavy barbell squat without a rack or spotter is a different proposition, and load should be regulated more conservatively there.

It is also a useful auto-regulation tool. Prescribing a rep target at a given RIR lets the weight follow your day rather than forcing a fixed number through poor sleep and stress.

In practice, aim for 1 to 3 RIR on most working sets, log what you actually did, and let our double progression planner decide when to add load.