Imagine: you are at the start for an international slalom in the heart of the Alps. 40 cubic metres of water thunder past you every second, and you are in a little boat weighing barely 20 pounds. Your mind is so focused that you can't even hear the water. You are thinking only about the 18 gates that you must not miss. Above all, that key sequence, the one that has already put paid to some competitors' hopes after months of training.

5 beeps from the electronic starter. At the 5th, you're away.

The first part of the course has been designed to tear your arms off. On the bank, your supporters are going crazy - but you can hear nothing. You haven't cleared one gate before you focus on the next.

Half the course done. So far, no touches. Your arms are getting pumped, your body is steaming despite the chill of the river. Now, the key passage. Total concentration. One slip will destroy you. Triumph or disaster is here, and you know it.

You're through. Rising confidence: you push harder still, though your arms are nearly paralysed. You must stay focused, you could blow it even in the last gate. And you are there. The final sprint. 10 metres to the finishing gate. 10 metres. Eternity.