And Moses Kiptanui, a three-time world champion from Kenya, said earlier this month that doping is taking place in the country's famous running camps.
So how widespread is the problem and what is the sport doing about it?
- Scott Douglas, editor of Runner's World Newswire. He is author of "Runner's World Complete Guide to Minimalism and Barefoot Running," which comes out March 12.
This segment aired on February 28, 2013.