Ultra running over ultra distances.

Up and down, ultra mountains or across the desert.

You might not think a business model based on people running exhausting distances would get very far,

but ultra running has become phenomenally popular.

I'm John Lawrence and for Business Daily on BBC World Service.

I've come to Nice, the French city, between the Alps and the sea, to look at the ultra business.

At the Alpine ski resort of Oron, 575 people are feeling pretty psyched.

They're going to pit themselves against the Ultra Trail Nice Cod d'Azure 100 miles,

and the race is about to start.

You feel a bit nervous?

Yeah, totally nervous.

This is one of the most punishing sporting competitions known to man.

An ultramarathon is anything more than a marathon, which is 42 kilometres or 26 miles.

This one is four times a marathon.

And whereas marathons are usually run over flat terrain, this 159 kilometre course goes over four high mountain peaks with a total elevation gain of 8,200 metres.

Think running up the steps of a building that's five miles high.

Out of those who make it to the finish line on the Promenade des Angles on the seafront in Nice.

The fastest will get there tomorrow after running through the night, the others the day after.

Their extra punishment for being slow, they have to run through two nights instead of one,

which is, they tell me, when the hallucinations start.

To make things more interesting, the weather forecast is for rain, sleet and snow.

Technically, I am a director at Lignocyte, which is a sustainable masonry company,

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