Maximal Reproducible Return

Two runners line up for the same run. Same fitness, same preparation.

The first runner feels good and settles into a good pace, not too slow, not too fast. He could go faster, but doesn't and finishes strong on even splits.

The second runner also feels good, but his ambition does the pacing for him. He goes out fast, too fast, past the pace his body can handle. It catches up with him and soon he is forced to drop his pace to a walk. After some time he recovers and finishes, but the collapse has cost him far more than the surge ever bought. He has a personal best for the first kilometer but finishes far below what he would have been capable of.

There is a name for the line the second runner crossed. The lactate threshold is where your body makes lactate faster than it can clear it. Below it you're aerobic. You can hold the effort for hours as the rhythm settles and even strengthens as you go, but cross it and you start spending a reserve. One runner stayed under, the second didn't.

Two ways to run the same distance

The surge over the threshold buys a few early seconds and then costs far more when the pace collapses. Runner two ends the run averaging well below the steady pace he could have held the whole way.

One run is just one data point. A season is many of them, won by how many good efforts you can stack. The runner who stayed under the line shows up again tomorrow, then the day after. The one who pushed too hard needs a disproportionate amount of time to recover. Stephen Seiler an exercise physiologist and professor of sport science studied where endurance athletes actually improve (2010). The ones who get fastest keep the large majority of their training below the lactate threshold. ​Staying under the line most of the time does not mean never going hard. Improvement still needs a small share of hard sessions above the threshold. The point is to do them rationed and deliberate, not letting ambition do them every day.

We are often the second runner, without noticing and buy a brilliant Tuesday with Wednesday and Thursday.

The most you can do again

Maximal Reproducible Return is the highest performance a system can reach again and again, reliably, across many attempts. Luca Dellanna sketches the idea in Winning Long-Term Games (2024). The maximum and the repeatable maximum are governed by opposite instincts. Reaching the absolute maximum means spending everything you have, squeezing out the last drop. The repeatable runs the other way, as it rewards easing off an effort you could obviously have pushed harder. You stay conscious of the capacity you deliberately leave unspent.

The records and the extraordinary performances are admired. Therefore we often push hard in persuite of them, which makes easing off feel super unremarkable, boring and unexciting.

The cost of chasing the max

An all-out reach for maximal performance drains a reserve, that does not refill on the same terms as it emptied. Draw it down a little and it tops back up fast. But draw it to the floor and the way back is harder than the drop that emptied it.

When putting numbers on it the asymmetry gets clearer. Lose twenty percent and then gain twenty percent and you are not level, you are at ninety-six. Lose fifty and you need a full hundred just to break even. The deeper the hole, the steeper the climb.

The climb back is bigger than the fall

The drop and the climb cover the same distance, but as a percentage the way back is always larger and it accelerates as the loss deepens. A fall of fifty percent needs a gain of a hundred just to break even.

When stringing periods together small swings of a steady path leak not to much, while the big swings one bleed growth on every recovery. The American finance executive and investment manager Thomas E. Messmore named that shortfall variance drain, though it is better known now as volatility drag (1995).

A reputation is built slowly, one kept promise at a time, but a single overpromise you cannot deliver takes a bite out of the whole stack of trust behind it. A bank account that doubles and halves and doubles again ends up behind the stable one. Each of these has a threshold of its own, unmarked and easy to miss, where doing a little more now borrows quietly from your ability to do it at all later.

The lines you don't come back from

Everything so far has assumed the reserve refills. Draw it down, wait and it comes back, probably slower than you would like but it comes back.

Some crossings are irreversible. You recover, but not all the way and the capacity returns lower than it left. A tendon pushed too far might heal shorter and stiffer than it was or reputation that took a hit rebuilds, but the trust settles a notch under the line it used to hold. You keep going, but from a floor that has dropped and will not climb back, where it was before.

Others are absorbing, where you do not recover at all, because there is no afterward to recover from. Stacking good efforts only counts if there is a tomorrow, where it can be counted again. Same for the average of your performances. It is only yours to collect if you are still there to collect it. Injuries that end your ability to perform in future events, scandals that end your career or investments that blow up, are all absorbing states.

Three kinds of lines

On the left the capacity comes all the way back, but the climb runs far longer than the fall. In the middle it recovers only part-way and settles under the old ceiling. On the right it drops to the floor and stops, with no afterward to recover into.

So the cost is either time, a lower capacity or the ability to continue. Staying conscious of the capacity you deliberately leave unspent can help you stay clear of them.

The score is the sequence

This asks for a change in what counts as winning. Success stops being a single result and becomes the run of results you can put back to back. The question shifts from: How much can I do? to How much can I do over the long run?

The first runner wakes the next morning and goes out again. And the morning after that. He never posted the fastest single kilometer in the group. Yet after a year of quiet mornings he is the one none of them can stay with.