In 2010, four of the greatest undefeated mountain runners on earth toed the starting line at the Western States 100-mile endurance run, the oldest and most prestigious 100-mile foot race in the world. 'Unbreakable: The Western States 100' follows the four lead men on this amazing journey. Hal Koerner, two time defending Western States champion, and running store entrepreneur from Ashland, Oregon. Geoff Roes, undefeated at the 100-mile distance, an organic chef from Juneau, Alaska. Anton Krupicka, undefeated in every ultramarathon he has ever started, a graduate student living in Boulder, Colorado. Kilian Jornet, the young mountain runner and two time Ultra-trail du Mont-Blanc champion, from Spain.

• Documentary