On the last Monday of August, at just before midnight in the Italian Alps, Colorado resident Careth Arnold was on her mark, preparing to take off through a series of ascents and descents that would take her into France.

The 35-year-old was taking part in a 95-mile endurance running course for the next 23 hours. Her first six and a half hours running was in pitch-black darkness, with "a lot of climbing dirt" and "chunky sections," she recalls.

The trail race across the Alps, with eight steep climbs and descents adding up to 29,527 feet of elevation gain, is the Sur les Traces des Ducs de Savoie, or TDS, and is part of the Ultra Trail du Mont Blanc series of endurance races. TDS was born in 2009, and had never been won by an American. Until last week.

"A little after the 50K point, the

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