Scott Gall has already beaten Chronic Fatigue Syndrome. So, he is respectful, if not exactly worried, about the challenge ahead when he competes in this weekend’s Pikes Peak Ascent.

The 13.32-mile race to the summit on Saturday morning starts a two-day event that finishes with the Pikes Peak Marathon on Sunday.

Gall, 37, of Cedar Falls, Iowa, contracted the Epstein-Barr Virus, which attacked his body’s auto-immune system, and led to chronic fatigue. It forced the five-time U.S. mountain running world championship team member to quit competition for four years.