reckoner
The last rep is where the growth is. Everything before it is a warm-up for the one that counts, and a set you walked away from with something left is a set you wasted. Almost everybody who lifts has been told some version of that, and it has a real argument behind it: as a set gets closer to the point where no further repetition is available, more repetitions are completed and muscle fibre activation progressively increases2.
The argument is sound. What it does not tell you is how much the last rep is worth, or what it costs, and both of those have been measured.
What the comparisons found
Grgic and colleagues pooled 15 studies comparing training to failure against stopping short of it. For strength, no significant difference. For muscle size, no significant difference. In the studies that did not equate the training volume between groups, stopping short actually came out ahead for strength1.
Refalo and colleagues asked a sharper version of the same question across another 15 studies, splitting them by what each one actually meant by failure. Stopping at set failure, however a study defined it, carried a trivial advantage for muscle size. Going to the point where no further repetition can be completed carried none at all. And pushing a set closer did not reliably buy more, which is why they describe the relationship as potentially not a straight line2.
Where the two goals part company
Robinson and colleagues did the version that treats closeness to failure as a dial rather than a switch, running meta-regressions on how many repetitions were left in reserve. The two outcomes came apart. Strength gains were similar across a wide range of repetitions in reserve. Muscle size improved as sets were ended closer to failure3.
So there is no single answer to give you, and anybody who has one is answering a question you did not ask. If you want to get strong, how close you go appears not to be the lever. If you want to get bigger, going closer is worth something, and it is worth something in a modest and continuous way rather than at one magic point.
Failure is not the price of progress. It is one of the things you can spend to buy some.
What it costs, which is the half nobody prices
Every comparison above is about what failure earns. Refalo and colleagues also reviewed what it takes. Sets taken to failure likely produce more neuromuscular fatigue, more muscle damage and more discomfort after the set than sets stopped short, and those may go on to impair the session you do next, the recovery in between, and how likely you are to still be training in a year4.
That last one is not a soft consideration. The training studies run for weeks. Your training runs for decades, and a method that makes every session something to be survived has a failure mode no meta-analysis will find.
What is genuinely unsettled, said plainly
There is no agreed definition of failure in this literature, and how close the people in the non-failure groups actually got is often unclear4. The repetitions in reserve behind the dose-response analysis were estimated from the descriptions in each study rather than measured, and its authors call the work exploratory and ask for caution reading it3.
Which means the direction is reasonably clear and the dose is not. Take anybody offering you an exact number of reps to leave in the tank as somebody who has decided rather than somebody who knows.
What to do on Tuesday
- If strength is the goal, you do not need it. Across the comparisons, stopping short cost nothing, and in one analysis it was ahead.
- If size is the goal, get close and understand you are buying by the inch. Closer is a little better. It is not a threshold you cross into a different category of result.
- Decide before the set which ones get it. Failure is something to spend deliberately, because the cost is real and it is paid by the sessions after this one. Discovering afterwards which sets went to failure means it was spending you.
- Never use it to find out whether you worked hard enough. That is a question about what you lifted and what it took, and there are better ways to answer it than by putting a bar on your chest.
- Watch what it does to whether you keep going. Sticking with training over the long run is one of the things the review names as something failure may cost4, and a program you quietly stop doing is the most expensive one there is.
What Reckoner asks for
Reckoner never asks for a set at the top of the effort scale. Every set it prescribes is written with repetitions still in the tank, and the top of the scale is reserved for what you report rather than for what the plan requests.
What you report is read against what that lift was asked for. Taking a set to the point where nothing more was available is neither progress nor a stall: it is not an error and it is not disobedience, and it does not by itself move a load in either direction. The reps you completed against the target decide what happens to the weight. The effort you reported decides whether you are being asked for too much.
When a lift keeps coming back harder than it was asked to be, the first thing that changes is the rest between sets, because that is the cheapest thing in the session to spend. Then a rep comes off the target. Then the volume or the load. It never takes a set away to treat a problem caused by not resting enough. Here is that happening, run through the engine now:
| Week | Prescribed | What it did |
|---|---|---|
| 1 | 4 x 10 at 60 kg | Load up 60 kg → 62.5 kgYou hit the top of the range at RPE 9, so the bar goes up 2.5 kg to 62.5 kg. The weight went up, so the reps come down to eight. You are now working 6 to 10. You finished every set that was asked for, which is what earns it. |
| 2 | 4 x 8 at 62.5 kg | Backed off 4 → 2 setsThis lift has been over what it is asked for two trained weeks running, so Reckoner takes about 40% of its sets off for one week rather than waiting for the block to do it. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue. Nothing else in your week moves. You have also been over what this lift is asked for two trained weeks running, so the rest between sets goes up from 150 seconds to 210 seconds. Nothing else about the lift moves. |
| 3 | 2 x 8 at 62.5 kg | More reps 8 → 9 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to four sets. |
Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.
The lifter in that run did the work and reported it honestly. Nothing about it was a mistake, and nothing about the answer is a punishment.