The Kenyan was tested in late September before defending her Chicago Marathon title.
Do you know what's really in your sports nutrition supplements?
The 8-time U.S. road champion says he is retiring from the sport.
The training partners of runners on performance-enhancing drugs probably also benefit.
The 37-year-old tested positive for a banned substance last year at a race in Mexico.
The long-term metabolites method can detect steroids that were taken more than six months prior.
The two-time American U.S. in the steeplechase considers himself to be a man of the people.
David Rudisha's coach says they are looking for an "extra edge."
The repeat gold medalist is adamant that he's clean.