Training science

The exercises that cost you least aren't there to build muscle

Seventy-seven of the 272 movements in the Forta database sit at the lowest neural cost there is, 2 out of 10. Sixteen of them are the hypertrophy machines from the last two articles. The other sixty-one return less stimulus, on purpose, because growing muscle was never their job.

Alfredo Silva · Sports Scientist MSc Physical Education · MSc High Performance Training 77 of 272 movements analysed

Seventy-seven movements in the Forta database carry a neural cost of 2, the cheapest rating on the 1–10 scale used across this blog. Sixteen of them were the subject of the last article here: pure isolation work sitting at the ceiling of stimulus-to-fatigue, a ratio of 4.50. This one is about the other sixty-one, and why a lower stimulus number does not mean a worse exercise.

Look inside the cost-2 tier and it is not one group, it is four. Stimulus inside it ranges from 9.0 down to 7.0, and the movements that make up the lower end are not weaker versions of a leg curl. They are a different category of exercise entirely — mobility work, activation drills, breathing, and the specific strength exercises that show up in injury-prevention trials rather than hypertrophy studies.

Four tiers wearing one price tag

Split by stimulus, the cost-2 group breaks down like this:

The 16 build muscle efficiently. The 61 underneath them mostly do not — and were never trying to. A Nordic Hamstring Curl and a Cable Lateral Raise sit at the same price, 2 out of 10 on the nervous system, but they are not competing for the same job in a programme.

What the other sixty-one actually are

A sample from across the three lower bands, so the shape of it is concrete rather than abstract:

Two of these are not obscure. The Nordic Hamstring Curl and the Copenhagen Plank are among the most studied single exercises in hamstring and groin injury-prevention research: the Nordic curl for reducing hamstring injury risk in team-sport athletes (van Dyk 2019), the Copenhagen adduction exercise for reducing groin injury incidence in footballers (Harøy 2019). Neither is going to move the needle on quad size. Both are why the athlete performing them is still available to train in November.

A cost-2 movement, at its worst, still returns 3.50 units of stimulus per unit of fatigue. The best movement at cost 10 returns 0.60. Even when the cheap tier is not trying to build muscle, it still beats the most expensive tier on this ratio by almost six times over.

Why "insurance" is the right word

Cost, in this model, measures how much a movement draws on the central nervous system — not how effective it is at any particular job. That is why a breathing drill and a leg curl can sit at the same price. What differs is the return each one is built to generate. The leg curl's return is a hypertrophy signal. The Nordic curl's return is a lower injury rate on a muscle group that, once torn, keeps an athlete out for weeks. Neither number is more real than the other. They are answers to different questions.

An insurance policy does not increase your income. It stops one bad event from wiping it out. That is what the 61 movements below the isolation tier are doing in a programme: keeping the shoulder, the hamstring, the groin and the ankle available for the cost-8-to-10 work that actually drives adaptation, without spending any of the budget those sessions need.

What this tier cannot do

Read this as "skip the heavy work, do banded walks instead" and you have read it wrong. None of the 61 movements here develop maximal force, none of them build meaningful muscle mass, and a programme built only from this tier will leave an athlete weak and undertrained no matter how consistently it is followed. Their value is that they cost almost nothing and protect something else. That is a real return. It is just not the same return as a leg curl's.

On a very low readiness score — the kind of morning that would make a heavy session a bad idea entirely — this is the tier a session can be built from without asking anything the nervous system cannot currently give.