[ALSO READ: Desiree Linden and Yuki Kawauchi Pull Off Boston Marathon Upsets]

The story of Tim Don, the Ironman king and Boston Marathon runner, is in many ways the embodiment of elite endurance athletes. At age 40, Don has a finite window for his body to withstand peak performance. There is the looming need to support himself through sponsors, who tend to compensate wins, not effort. And aside from childhood jobs as a paperboy and a lifeguard, he has single-mindedly devoted his life to reaching the pinnacle of his sport.

“If you’re a surgeon and someone runs over your hand, you’re still going to try to get back,” he said. “I’ve never had another job, and this sport is my way of life. I don’t know any other way.”

In October, Don was preparing for the Ironman world championship in Kailua-Kona, Hawaii, and went out for his final prerace bike ride. He was warming up when a car smashed into him on the highway.

Instead of the career-defining medal he had sought, Don wound up with the halo. For three months, he passed much of his time motionless in an armchair as his vertebra healed at his home here. He could not dress, shave or shower. His forehead swelled, and the holes where the pins were screwed in began to ooze. When his wife tried to clean around the metal with a sponge, Don nearly passed out from the pain.