Effort, repetitions in reserve and failure
How hard a set should feel and where it should end.
The short answer
A productive set becomes genuinely difficult while the movement remains recognisable; for beginners, stop before another correct repetition becomes unlikely.
Repetitions in reserve
Repetitions in reserve, or RIR, estimates how many more clean repetitions you could have completed. It is a judgement, not a measurement. The adaptation phase lets you compare easier and harder sets until the estimate improves.
Technical failure is the stopping rule
Technical failure is the point where the next repetition would require a shorter range, bounce, swing, assistance or major change in posture. Absolute muscular failure is not required, and some exercises should never be deliberately taken there.
Remember: Stable machines tolerate hard effort better than movements where fatigue can compromise balance or spinal position.
Lesson finished?
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