If you want to examine this topic from strictly a cycling perspective, watch the DVDs "Bicycle Dreams" and "Race Across America" by Stephen Auerbach, read "Hell on Two Wheels" by Amy Snyder. You'll find the answer is that a combination of physical and mental training are key in the ability to perform at a high level. There's also a bit of fortune in the mix, I believe. Mental toughness is a HUGE part of how RAAM solo riders ultimately succeed and / or fail, as well as HOW effectively they do either. When it comes to athletic excellence, the mind is a terrible thing to waste...