The distance that Saunders and L'Herpiniere will ultimately cover over the course of the 110-day expedition will amount to 70 consecutive marathons – a grueling test of endurance that will push their lungs to the brink on a daily basis. In preparation, Saunders pulled out all the stops during the last year of training, trying anything and everything to get himself into the best shape of his life. "When I'm in London, it's a lot of running and cycling, and if we're farther afield, it's in the hills with a pack on or skiing," Saunders says. To keep up the regimen, he says he relied on the kindness of sadistic training partners. "I've kind of surrounded myself with people who can kick my ass in whatever it is – the guys who I run with are way stronger and faster than me." he says.

That, it turns out is a good strategy. Saunders recently ran a marathon in two hours, 55 minutes – muscles and all. "Getting to that point has been fun," he says. "I've proved quite a few wrong along the way who said it couldn't be done."