It was approaching sunset on a mid-February Saturday in the mountains of Flagstaff, Ariz. A couple hundred people were at the base of the local ski resort, ready to race — not downhill, but up the slope, sans chairlift, either on skis or with micro-spikes strapped to their running shoes. They would ascend 2,200 vertical feet before they slid or clomped the whole way back down to the finish line, where beers and snacks would await their arrival.