Nepal, July 20 -- second when a hamstring tears at full sprint, in which the body keeps believing it is still running. Aayush Kunwar was through the bend of the 200 metres at the 2024 National Games-into the straight where the race stops being about speed and becomes about holding your shape while your legs come apart-when the muscle in the back of his right thigh gave way. He pulled up and limped off the track; the race gone, the season with it.

I should explain why that matters now. This July, on a track in Los Angeles, Kunwar ran the 200 metres in 21.87 seconds. The Nepali national record, 21.92 seconds, had stood since 1995-the year he was born. It had outlasted three decades of sprinters who came and went without touching it. Nor di...