The world's most extreme challenges

Last updated at 13:18
Runners across the desertGetty Images

British adventurer Sir Ranulph Fiennes is running the Marathon des Sables, which some call the toughest race in the world.

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Jenny reports on Sir Ranulph's 'toughest race'

He will have to travel more than 150 miles across the Sahara desert, in temperatures of 50C and carry all his supplies while he runs too. But is it the most difficult race out there?

Here's Newsround's guide to some of the toughest challenges in the world...

It's a great challenge for cross-country skiiers.AP

The Arctic Circle Ski Race

The ultimate endurance race involves skiing 100 miles across the Arctic in temperatures as low as minus 50C. It lasts three days and the nights are spent trying to keep warm in tents. Skiiers are accompanied by supporters travelling on sleds pulled by dogs.

Amazon rainforestGetty Images

Jungle Ultra

The newest event on our list claims to be the race to end all races. The Jungle Ultra requires you to travel through the Amazon Rainforest in Peru. Carrying your hammock (to sleep on each night), food supplies, sleeping bag and the rest of your kit. Runners go through jungle trails and wade through 70 river crossings, spending the evenings in the villages of local tribes.

Yukon River quest

Yukon River Quest

The world's longest annual canoe and kayak marathon is 444 miles through the Yukon River, in North America. Participants race around-the-clock for five days in freezing waters. The event takes place in the summer so there is 24 hours of daylight, which is why some people call it the Race of the Midnight Sun.

Car racing across the desert in the Dakar Rally.AP

Dakar Rally, South America

This race across South America is open to professional and amateur drivers who can choose to travel by car, truck, quad bike or motorcycle. It is a coast to coast journey through Argentina, Chile and Peru across the Andes Mountains, the Atacama Desert and between the shores of both the Atlantic and Pacific Ocean.