There is a marathon in the Sahara Desert. It is 75 kilometres long. The best runners finish it in seven hours. The slowest runners can run for up to 30 hours. Most people start at the same time. The best 15 men and women start later.

The marathon is not easy. People know this. It is very hot. It is very important to drink a lot of water. It is also important not to start very fast.

The way is also difficult because it changes. Sometimes the marathon goes up or down very much. The runners have to change their speed too.

There is a marathon in the Sahara Desert. It is 75 kilometres long and the quickest runners finish in seven hours. The slowest runners may run even for 30 hours. Most of the runners start at the same time. The top 15 men and women start a few hours later.

Everyone knows that the race is not easy. The runners have to drink a lot of water and not run very fast at the beginning. It's not just the terrible heat that makes the race hard. The terrain changes and the runners have to change their speed too.

Ahead of them 75 kilometres of burning Sahara Desert. For the quickest it takes around seven hours, for those further down the field up to 30. Most of the runners are sent off at the same time with the top 15 men and women a few hours later. They are in no doubt about the challenge that lies ahead.

"It's gonna be a long day, so just concentrate on looking after your body for the whole way, eating at the right times, drinking enough. That's nothing. If you go too fast at the beginning, you're in trouble."

It's not just the searing heat that makes this stage grueling. The terrain changes and so too with it the pace. For some, maintaining spirits is easier than others. Runners have got a long way to go in this competition. This is just the fourth stage of the Marathon de Sables. At least, they can look forward to a rest day after this race.