Stephanie set out for an ambitious summer challenge: take on the brutal Maah Daah Hey 100 in North Dakota and, just one week later, line up for another 100 miles at Lean Horse in South Dakota. But before she even reached the starting line, routine bloodwork finally gave her an explanation for months of struggling to regain her speed—extremely low ferritin. With only days to address it, she headed north anyway, determined to find out what her body could do. Joined by American record holder Jen...