ON CERTAIN WEEKDAY MORNINGS, AROUND 5.30 or 6am, a small group of athletes gathers at a trailhead in Boulder, Colorado. From there they run a kilometre or two along the dirt trails that snake up to the base of the mountain, gaining elevation as they hop over rocks, roots, and whatever obstacles lie in their path.
But when they near the Flatirons, the iconic slabs of rock that overlook town, the real adventure begins. Instead of reversing course as many runners do, the athletes forge ahead to the base of the rocks. Without breaking stride, they lean forward, place their hands on the rock, and continue their skyward journey, scrambling up the massive sheets of sandstone, typically without the safety or comfort of any climbing equipment – relying just on…