Extreme sports have always taken the trail less shredded. See rock climbers, mountain bikers, kayakers and other inventive athletes return to their roots to practise their sports in nature. They'll accept any challenge nature presents, resulting in some of the most gasp-worthy stunts ever seen. See the first person to climb Yosemite's El Capitan with no ropes. Watch high-liners walk a tightrope between cliff edges. Discover how you can get outdoors and find your own "adrenalin buzz". Part of the Natural Thrills series.