Twenty-six miles is a long way to travel on two legs, but last year alone, 541,000 runners across the country completed marathons. Here in the Centennial State, running a 26.2-miler—not to mention the 100-mile ultramarathons, 24-hour endurance challenges, and extreme mountain races for which our state is famous—is practically a rite of passage. But it got us thinking: How healthy can all that pavement pounding and oxygen depletion really be? We asked Dr. Iñigo San Millán, director of the Human Performance Lab at the Anschutz Health and Wellness Center, to walk us through a marathon’s effects on the average body.

5280 Health 2015
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—Bryan Christie Design