It was during breakfast, the morning after completing the Marathon des Sables and whilst recovering in Ouarzazate's Berbere Palace, that discussions began as to what should come next. The Marathon des Sables was no longer recognised as the toughest footrace in the world, at least not by those on the ultra-endurance adventure racing circuit. The general consensus was that the true toughest ultra took place in the heart of the Amazon jungle, and it had a staggeringly high drop-out rate.The Jungle Marathon is probably the toughest 'multi-stage' footrace in the world. The terrain and combination of heat and humidity make this event far more arduous than races held in desert environments. 'The Jungle Marathon: Ultra Endurance Running in the Heart of the Amazon', is the story of this epic adventure, told by exercise physiologist Mark Hines. It is about the training and preparation, the extreme physiological consequences of exercise in such a climate, and what it is to race in one of the world's most extraordinary and incredible environments.