Bill Pierce, a professor of health sciences at Furman University and the co-founder of the Furman Institute of Running and Scientific Training, said it was nearly impossible to project an elite girl’s future success in distance running because the female body changes so much during the teenage years.

Running fast over long distances requires great lung capacity, but also great strength relative to body weight, as do figure skating and gymnastics.

“They are nothing but skin and bones and lungs in their early years,” Pierce said. Then, he said, the girls mature but don’t necessarily develop the strength required to move a larger body so swiftly.

It’s hardly a coincidence that many girls at the top level of the sport as juniors have struggled with disordered eating and other body-related issues. They include Melody Fairchild, who in 1991 was called the greatest high school runner ever. Fairchild dreamed of making an Olympic team from the age of 12, and she was such a dominant runner as a teenager she was certain it would happen. It never did.

Now 44, Fairchild understands where her dream went off course. Her personal life fell apart the summer before college. Fairchild’s mother died of cancer 25 days after she graduated from high school. Her father battled alcoholism. Fairchild struggled with injuries her freshman year at the University of Oregon.

Looking back on those years, Fairchild said she, like so many other young, talented runners, failed to understand that the ups and downs she experienced as her body evolved were normal. Nature was doing what it is supposed to do for young girls as they become women — add fat and prepare the body for reproduction. That otherwise healthy development, however, does not help an elite runner maintain her speed.