A hard set and a useful set are not always the same thing. Finishing every set only when another repetition is impossible may feel decisive, but it also removes an important coaching choice: where the set should stop inside the wider workout.
Instead of treating failure as proof of effort, use a planned stopping point. That point can change by exercise, training phase and experience. The purpose is not to make training easy. It is to make effort deliberate enough that you can record it, repeat it and adjust it.
Define the terms before using them
Momentary muscular failure generally means reaching the point where you cannot complete another repetition with the intended technique. “Repetitions in reserve,” often shortened to RIR, is an estimate of how many good repetitions you believe you could still perform when you stop.
For example, stopping at an estimated two RIR means you believe approximately two more repetitions were available. It is an estimate, not a laboratory measurement. Newer lifters may need time and coached practice before their estimates become useful.
Technique still matters. If your planned movement changes substantially, the set may already be over even when the weight continues moving. Do not trade the agreed exercise for twisting, bouncing or assistance that was not part of the plan.
Understand the fatigue trade-off
A 2023 randomised crossover study compared six sets of bench press performed to failure, one RIR or three RIR in 24 resistance-trained adults. Moving closer to failure produced greater immediate loss of lifting velocity and higher reported discomfort, exertion and soreness. This was one controlled bench-press protocol, so it does not establish one universal stopping rule for every person or exercise.
The practical point is that the final repetitions have a cost as well as a training stimulus. Your programme has to account for the next set, the next exercise and the sessions that follow. More immediate fatigue is not automatically evidence of a better long-term result.
Give each exercise a stopping instruction
Look at your programme before the session. A useful entry includes the exercise, target repetitions, number of sets and an effort instruction. If the effort target is missing, ask your coach instead of assuming that every set should end at failure.
Example: a controlled machine exercise
Your programme might ask for three sets of eight to twelve repetitions with two repetitions in reserve. You select a load, complete the set with the intended technique and stop when you estimate that about two good repetitions remain. You then record the load, repetitions and estimate.
Example: an exercise needing more caution
For a technically demanding movement, your coach may give a different stopping rule: end the set when technique changes, when the target RIR is reached or when a spotter instruction applies—whichever comes first. Do not invent a failure test on an exercise you cannot safely exit.
These examples explain how instructions can be written; they are not personal prescriptions. Exercise selection and effort targets should reflect your experience, health, equipment and supervision.
Use the first set as information
Suppose the plan calls for ten repetitions at two RIR. After the first set, you believe you had five repetitions left. Rather than adding random extra repetitions, record the mismatch. Your next-set adjustment should follow the progression rule in your programme.
The opposite can happen too: you reach eight repetitions and the next good repetition is doubtful. Stop according to the agreed rule, record what happened and avoid forcing the target merely to make the log look complete.
One imperfect estimate does not ruin a session. Consistent notes help a coach see whether the planned load, repetition range or effort target needs changing.
Review patterns, not one dramatic set
At the end of the workout, check three things: Did technique stay consistent? Were your RIR estimates reasonably similar across comparable sets? Did performance collapse more than expected? Add a short note about sleep, unusual stress or equipment changes when they clearly affected the session.
Do not turn RIR into a competition to prove toughness. The value is in giving your coach a shared language for effort. Some programmed sets may be closer to failure; others may intentionally stop earlier. Both can belong in a structured plan.
Stop if you feel sharp pain, dizziness or symptoms that concern you, and seek appropriate professional advice. An effort scale is not a tool for training through warning signs.
Train with a defined progression plan
URWRU Fitness Coaching provides personalised training, technique support, progress tracking and coaching around your schedule. A coach can define how hard each exercise should be and how to adjust it over time. Visit the Fitness Blog for more practical training guides.