For the first two miles, everyone waited and watched, clipping their strides and listening to the rasp of their competitors’ breathing. Finally, the Kenyan pair of John Korir and Reuben Cheruiyot, who between them had won the last three editions of the race, hit the front. The pace surged; the nervous energy of the tightly bunched pack was exhaled, and the race was on.

In a sense, every stride you take during a race is a microdecision: will you speed up, slow down, or maintain your current pace? But some decisions are more consequential than others. As Korir and Cheruiyot telescoped away, leaving the shrapnel of the exploded lead pack in their wake, I had to decide how hard to chase. I wasn’t concerned about pace or splits; I had logged enough miles on the razor’s edge, over the previous decade, to be able to feel in my gut precisely what was sustainable and what wasn’t. I was as fit as I had ever been, and—let’s be honest—wanted cash; but I was also disciplined and pragmatic. As the runners around me abruptly launched into what seemed like a near-sprint, I accelerated more steadily, hoping to hit the the maximum pace I could sustain for the eight remaining miles. Soon all two dozen runners in the lead pack were receding into the distance in front of me. But I hoped to see at least some of them again.

My memories of the second half of that race are still vivid—the thrill of the hunt as, one by one, I began to track down and pass the stragglers. Some of them put up a brave fight. Others were barely jogging; you could almost see the metaphorical cloud of black smoke billowing from their overheated engines. Late in the race, I caught Simon Rono, a Kenyan who a few years earlier had notched the second-fastest winning time in the race’s history, to move into twelfth place. I was in the money! With a few hundred yards remaining, some friends cheering on the sidelines pointed up the road to another Kenyan runner wobbling toward the finish. I lowered my head and charged, edging him just before the line to increase my payout from $200 to $250.

For years afterward, I told that story as a tale of triumph—a humblebrag about my finely honed pacing acumen. Knowing my limits and racing with them within allowed me to beat half the elite runners in the race. I am eager to learn more, in the coming years, about which signals my brain responds to, how are those signals processed, and-yes- whether they can be altered. But it’s enough, for now to believe, to know when the moment of truth comes, science has confirmed what the athletes believed: that there is more in there- if you are willing to believe it.

This is an extract from Alex Hutchinson's Endure published by William Morrow