Salina Kosgei was the tenth and youngest child of poor farmers in the highlands of western Kenya. The family hut had no electricity or plumbing. As a kid, Salina used to run 10 kilometers to school, barefoot, just for the fun of it.

But where Salina grew up, running wasn’t just a hobby. It was a well-worn path to financial security. The best houses in her area belonged to runners who had made good.

So at 16 she decided to go pro. It was a long slog, with lots of ups and downs. Then one day she found herself elbow to elbow with the defending champ in the most prestigious marathon in the world, with the finish line in sight.