When a set turns genuinely hard, the last few repetitions feel decisive, as though everything before them was rehearsal for the moment the bar slows. For decades, lifters treated training to failure as the toll you paid for growth, the proof that a set had been worth doing. The evidence now tells a more measured story, and it changes how the final reps of every set should be judged. Proximity to failure, usually expressed as repetitions in reserve (RIR), describes how many m