LaShawn Merritt: Defending himself and his title

In the 2008 Beijing Summer Olympics, LaShawn Merritt earned gold medals in the 400m and 400m relay. In the winter of 2009, he failed three drug tests. This summer, Merritt is competing in the London Olympics, trying to overcome preconceptions about his past. Read the article, see a timeline of doping at the Summer Olympics or see more in this series on speed.

Article: Drugs’ long shadow

Speed: Chemistry

Every thrilling record-setting performance is now followed closely by suspicions. Today's athletes know that any personal breakthroughs will be greeted with, "What are you on?"

Timeline: Doping at the Summer Games

Timeline

Olympic athletes have tried to boost their performances since at least 1904, but nothing was against the rules until the late 1960s. Since then, cheaters often have been a few steps ahead of those who try to catch them.

Series: Profiles in Speed

Profiles in Speed

Speed will be a defining theme of the 2012 Olympic Games. How do athletes continue to get faster? What are the keys to speed, and increasing it?