But that is not how it works.

No?

No. I read about it. It is the muscle. The muscle runs out, and you stop. That is the whole of it.

Then tell me. All of it, from the beginning.

You want me to explain it to you.

I want to hear you say it out loud. That is usually enough.

In 1923 a physiologist called A. V. Hill put runners on a treadmill and measured everything they did. He decided fatigue happens in the muscle.

It does not. In 1997 Tim Noakes said it happens in the brain.

Hill said the muscle runs out of oxygen. That is why you stop.

Then measure yourself the moment you stop. The oxygen is still there. So is the fuel.

So the muscle fails.

The muscle is TOLD to stop. It is still able. It is being held back.

But Hill said the body breaks down. A catastrophe.

Nothing breaks. You are being protected, and you feel that protection as tiredness.

And Hill himself? Did he never think of this?

He did. One year later, in 1924, he wrote that something central must be governing the heart, protecting it.

But he had only reasoning, no evidence. So it was dismissed, and for seventy years everybody studied the muscle.

Then Noakes, St Clair Gibson and Lambert published it properly, five linked papers, in 2004.

The brain reads your pulse, your breath, your temperature, your water, your sugar. The whole time. And it decides when you stop.
