False start Q&A
What is the false-start rule as it stands? Any athlete who jumps the gun is disqualified. There are no second chances, as Usain Bolt today and Christine Ohuruogu yesterday found out to their cost.
How does it work?
False starts are detected by pressure sensors on the starting block. An athlete does not even have to cross the starting line to be disqualified - as was the case today with Dwain Chambers - as even a twitch can register on the sensors. Any substantial movement reaction within 0.1 seconds of the gun being fired is considered a false start, as research has shown human beings are incapable of reacting quicker than that.
When did the rule come into force?
The rule was okayed back in 2009 and officially brought in on January 1, 2010.
What happened before then?
Before then, the field was allowed a single false start. A second false start - even from an athlete who did not commit the first offence - led to disqualification.
Why was it changed?
Officially it was changed to prevent gamesmanship. IAAF president Lamine Diack said at the time: "The current rule gives sprinters the chance to play the system to deliberately false start but not be punished for it." There is a suspicion, though, the decision had as much to do with TV companies - false starts could play havoc with their schedules.
What was the reaction at the time?
It's fair to say many athletes were unimpressed. Former world champion Tyson Gay said, presciently as it turned out: "I don't like it one bit. If it happened at the Olympics or World Championships next year - without Usain Bolt the race is going to have an asterisk to the side. It just doesn't make sense."
Have any other high-profile athletes been affected?
Women's world and Olympic champion Shelly-Ann Fraser who fell foul of the rule at a Diamond League meeting in Rome last June. She said: "It was very devastating and I cried because this was the first time in my career something like this was happening to me. I hate this new false-start rule. I definitely do not like it."