Desc: Toughest Race on Earth with James Cracknell: With Elliot Challifour, James Cracknell, Jonathan Scott, Simon Wickes. James Cracknell takes on the Marathon Des Sables, a gruelling desert race in the Sahara. The race is considered to be the toughest on Earth; completing the equivalent of seven marathons in seven days and carrying all his food with him. Prior to the race, James investigates a scientific approach to training, acclimation and nutrition which involves a scientific evaluation against the Marathon Des Sables record holder.