“When I was getting into the sport, jumping into the marathon, people told me to wait and hold out — I needed to work up to it,” he said. “I said: ‘Whatever, that’s not true. I’ve been running 100 miles a week since I was 17, in high school, and I’m ready.’ But training at that level for so long takes a toll on your body for sure.”

He achieved early success, setting the American record for a debut marathon at London in 2007 with a time of 2:08:24. He attributes his current fatigue problems to that early training load and to unconventional training strategies throughout his pro career. Before the 2012 London Olympics, for instance, he did three weekly workouts at world-record marathon speed — a 4:42 pace per mile — pushing each session for as long as he could.

It is impossible to know for sure whether Hall’s extreme approach helped or hurt his performance. Would he have run even better times if he had not demanded so much from his body? Or did he have to train that way to find his peak? Regardless, he was the rare American marathoner who challenged the sport’s dominant athletes from East Africa. His landmark time for an American runner was achieved in an uncommonly fast Boston Marathon field. On a course ruled ineligible for an official record, he led most of the race at blistering speed until he was beaten at the end and finished fourth.

“I remember Wesley Korir telling me after that race that the Kenyans were afraid of me, and I thought that was ironic; I’d never heard of a Kenyan being afraid of a white person before in the race,” Hall said. “I think it showed the level of respect they have for me. I love that it ruffles feathers with them, but I don’t see any difference between them and me. White people can race Africans.”