You have to dodge snakes and scorpions as well as finding your way through sandstorms. At night when the competitors bed down in sleeping bags the temperature drops close to freezing.
Dave O'Brien is very brave to compete in this race.
Article by Maria and Melissa.
Dave will be up against 140 miles in 120 degrees of heat running across the Sahara. If a sandstorm should occur the runners are advised to stand still, not to sit or lie down, beacause they might get buried alive.
Additional reporting by Peter and John.