Lab Notes · 6 min read
Most of the repetitions people do in a gym build nothing. That is not a judgment on how hard anyone is working. It is a measurement problem, and I am going to show you exactly where it sits.
Two things have to be true at the same moment for a repetition to build anything. The large bundles in the muscle have to be switched on, which happens only when the job is too hard for the small ones. And the weight has to be moving slowly enough to load them once they are working. That second part comes from the force-velocity relationship. A fiber that is shortening fast produces less force than the same fiber shortening slowly.
A repetition where both are true has a name. It is called a maximally effective rep, and it is the only unit worth counting.
They are called junk volume. A junk rep is too slow to build speed and not fatigued enough to build muscle. It sits in the middle, so it produces neither adaptation. It still costs you recovery, because your body pays for the work whether the work bought anything or not.
That is where most of the extra sets in a workout go. They buy a recovery bill and nothing else.
Two groups of trained men squatted for eight weeks on the same program with the same loads. The only difference was when each set stopped. One group ended the set as soon as bar speed dropped off their best rep. The other kept going well past that point. The group that stopped early did far fewer repetitions, got at least as strong, improved their jump by more, and kept the fastest of their fiber types intact, which the harder-working group lost.
Pareja-Blanco et al., Scandinavian Journal of Medicine & Science in Sports 2017
The wider evidence says the same about grinding a set until you cannot complete another repetition. Pooling the controlled trials, there is no support for muscular failure beating a set that stopped short of it for muscle growth.
Refalo et al., Sports Medicine 2023;53(3):649–665
The standard instruction is to take the set close to failure and judge how many repetitions you had left. That judgment is called reps in reserve. When researchers pooled every study that tested it, people were wrong about how many they had left, and most wrong on lighter loads and earlier in the set, which is where most training actually happens.
Halperin et al., Sports Medicine 2022;52(2):377–390
So the standard method for deciding whether a rep counted is a guess, made by a tired person, about the thing they are least equipped to judge. That is why reps pile up. When you cannot tell which ones worked, doing more feels like the safe answer.
Working close to failure is correct, and we train that way. What we change is the endpoint you work toward.
The first endpoint is technical failure. You can still move the weight, and you can no longer move it the way the exercise requires. The pause at the bottom disappears. The position slips. The range gets shorter. The set ends there, because every repetition after it trains a different movement than the one we assigned.
The second endpoint is a velocity loss threshold. We measure the speed of your best repetition in the set, and the set ends when your speed falls past the amount the method allows. Which endpoint governs, and how much velocity loss is allowed, is set by the method you are on.
This is the part that almost nobody separates. When your speed drops on a strength day or a speed day, your neurological capacity for that load is spent, so we rest you ten to thirty seconds inside the set, called a cluster, and bring the speed back. When your speed drops on a muscle day, you have entered the metabolic growth zone, where the muscle-building stimulus is highest, so we extend it with a rest-pause or a drop set and keep you there longer.
Same reading. Opposite instruction. The reading is the only thing that tells you which one you are looking at, and in a normal gym nobody has it.
The whole gym runs on an AI-based strength measurement system. Artificial intelligence reads exactly what level of effort you are putting in on every repetition, and it makes sure you are in the right strength-building and muscle-building zone at all times.
The system reads your speed while the weight is still in your hands, so the endpoint of your set gets called by measurement rather than by feel. Your load for the next set comes off the same reading. That is what we mean by no junk reps. Every repetition you do here does one of the three jobs, and we know which one before you put the weight down.
Other gyms can read this and agree with all of it. Doing it means measuring every single repetition as it happens, and that is the one thing you will only find here.
Getting more out of every exercise.
Twenty-five minutes. No charge. You walk out with your numbers.
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