Try the meditation of the trail, just walk along looking at the trail at your feet and don't look about and just fall into a trance as the ground zips by," Kerouac wrote. "Trails are like that: you're floating along in a Shakespearean Arden paradise and expect to see nymphs and fluteboys, then suddenly you're struggling in a hot broiling sun of hell in dust and nettles and poison oak... just like life.

Faced with the almost inescapable conclusion that it had been selling lemons, Nike shifted into make-lemonade mode. Jeff Pisciotta became head of a top-secret and seemingly impossible project: finding a way to make a buck off a naked foot.

We're constantly told that running will ruin our knees and outrage our hearts, but for nearly all of human existence, it was associated with freedom, vitality, and eternal youth.

Running should be free, man.

That was the real secret of the Tarahumara: they'd never forgotten what it felt like to love running. They remembered that running was mankind's first fine art, our original act of inspired creation. Way before we were scratching pictures on caves or beating rhythms on hollow trees, we were perfecting the art of combining our breath and mind and muscles into fluid self-propulsion over wild terrain. And when our ancestors finally did make their first cave paintings, what were the first designs? A downward slash, lightning bolts through the bottom and middle-behold, the Running Man.

We've created an unnatural form of running. It's not just the shoes, but we run on artificial surfaces - straight ahead, hard and steady - instead of speeding up and slowing down, reacting to the terrain with changes of pace and rhythm.

But you can't muscle through a five-hour run that way; you have to relax into it like easing your body into a hot bath, until it no longer resists the shock and begins to enjoy it.