Ryan Hall, Fastest U.S. Distance Runner, Is Retiring

Photo Ryan Hall with his wife, Sara, and their four daughters, who they adopted in October from an orphanage in Ethiopia. Credit Elizabeth D. Herman for The New York Times REDDING, Calif. — Sprinting seven miles down a 9,000-foot mountain and then running back up to do it again may not appeal to even the most self-punishing of athletes, but Ryan Hall believes it is the kind of “experimental workout” that transformed him into the fastest American distance runner in history.

It is also the kind of extreme training that is now causing him to abruptly retire, two decades into an audacious career that produced national milestones — his time of 2 hours 4 minutes 58 seconds at the 2011 Boston…