Distance runner Dathan Ritzenhein announced his retirement Thursday, closing a career during which he made three Olympic appearances and also was one of the first to question the methods being used by his coach, Alberto Salazar, who is serving a four-year doping suspension.

In a farewell post on his social media accounts, the 37-year-old Ritzenhein wrote: “I won’t be on the start line, but I’ll never be far away. I won’t be in a rocking chair or out on the golf course. You’ll probably find me behind a stopwatch or cheering on the side of the road.”

Ritzenhein leaves the sport as the fourth-fastest American marathoner in history; he clocked a time of 2 hours, 7 minutes, 47 seconds in Chicago in 2012. He qualified for the 2004 and ’12 Olympics in the 10,000 meters, and also earned a spot in the 2008 Olympics marathon.

He was in the headlines last fall when Salazar, the leader of the Nike Oregon Project team, was banned for four years for his aggressive experiments using supplements and testosterone. According to the report detailing the circumstances that led to Salazar’s ban, Ritzenhein was one of the first of his athletes to question whether the infusions of a supplement called L-carnitine were being conducted in accordance with anti-doping rules.

Ritzenhein’s career was marred by injuries. In his post, he thanked his trainers and support staff for helping him overcome the ailments.

“I kept you very busy!” he wrote. “I had so many setbacks along the way. But I always had people who were there to help put the pieces back together and get me back on the start line.”

Ritzenhein was a standout at the University of Colorado, where he won a cross-country title in 2003 and finished runner-up in the 5,000 meters at the 2004 NCAA track and field championships.

“It was truly (an) amazing journey,” he posted. “I’m looking forward to the next chapter!”