When the world’s best cross-country skiers stand on the start line for the men’s 50-kilometer freestyle, the final race of the 2011 World Ski Championships in Oslo, they will do so alongside Sergey Shiriaev, a Russian athlete who served a two-year doping ban between 2007 and 2009 and continues to work with controversial coach Anatoly Tchepalov. Tchepalov is currently serving a ban of his own for connections with athletes involved with doping: a four-year sanction...