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“What they were trying to tell us, is no human can possibly move that fast.” 
Amanda Northrop / Vox

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Runners can be disqualified for starting after the gun. What gives?

The rules of elite running say no one can start a race faster than 0.1 seconds. Scientists say that’s wrong.

In July 2022, TyNia Gaither lined up in the second lane for one of her biggest races of the year: the semifinals of the 100-meter dash at the World Athletics Championships in Eugene, Oregon.

The 29-year-old Bahamian sprinter crouched down into the starting blocks. The crowd grew quiet. She waited for the sound.

“I heard the gun go off, and I took off,” Gaither says. “And then I heard the gun go off again.”

That second “bang” meant officials had stopped the race. Someone had false-started, and Gaither was surprised to find out it was her.

“I thought it was an error,” she says. “I’ve never false-started ever in my life.”

Per the rules, Gaither was immediately disqualified. When she tried to contest the call to the race official, he showed her a replay. It didn’t show a visible false start. But then he pointed to a number, lit up in red: 0.093 seconds, the amount of time it took for Gaither to start after the gun fired.

Yes: She had started after the gun went off, and was still thrown out of the race.

“I’m mind-blown,” she recalls thinking. “You’re telling me I’m penalized for something I did after the gun went off!?”

There’s a peculiar rule in top-level running that says if a runner starts within 0.1 seconds of the gun, they’ve broken the rules. The assumption made by World Athletics, the organization behind this championship, is that it is physiologically impossible to start that quickly.

“What they were trying to tell us,” Gaither says on Unexplainable — Vox’s podcast about unanswered questions — is that “no human can possibly move that fast.”

Any racer who does is presumed to have anticipated the gun, meaning their brains gave the “go” signal to their bodies before they heard the sound.

But is that… true? What is the fastest possible human reaction time to a sound?

The answer could vindicate Gaither, who feels unfairly labeled as a cheater — “there was no guessing in my start,” she says emphatically — and other athletes who have been similarly disqualified for starting too quickly.

But this question also leads to bigger ones near the heart of the sport. Competitions like track ought to reveal the limits of human abilities, to push through previously assumed boundaries. But, here, World Athletics seems to have set a limit that might actually be holding its athletes back.

What would be better? Does racing, along with other sports, need greater scientific precision, a better understanding of human physiology? Or does it just need to accept that there may not be a perfect way to define, and record, a race?

It’s true runners can’t react immediately. But how fast can they go?

According to scientists, the basic idea behind the 0.1 second rule does make some sense.

Human beings cannot react instantaneously to a sound, says Matthieu Milloz, a biomechanics scientist at the University of Limerick in Ireland who is completing his PhD on recording race starts. A long chain of physical and physiological events have to occur, and each component takes time: The sound of the gun has to travel to a runner’s ears, the ears translate the sound into a neurological signal, the signal has to be recognized by the nervous system, the nervous system has to send a command to start down to the muscles, the muscles take time to contract, and so on.

A wily racer could get a jump on this process. “You can anticipate the gun,” Milloz says. Races can be won or lost by hundredths, even thousandths of a second. So an early start can give a runner an advantage.

What doesn’t make much sense to scientists is the number World Athletics says is the neurophysiological limit. “Currently, we don’t know what this neurophysiological limit is,” Milloz says. “But what I can say is that the 100-millisecond [0.1 second] threshold is not science-based. We don’t have the data.”

TyNia Gaither competes in the women’s 100-meter heats on the second day of the 2022 World Athletics Championships.
Ezra Shaw/Getty Images

That’s not to say there haven’t been any studies. The studies on sprint starts tend to be small, and they don’t always use the most elite athletes as subjects. If scientists aren’t testing the very fastest sprint starters in the world, how would they know what the very edge of the limit is?

A 1990 Finnish study on eight non-elite sprinters is often cited, and this study did find evidence to support a 0.1 second limit. But other studies have recorded sprinters starting faster than that — perhaps even faster than 0.085 seconds. Other scientists have done some back-of-the-napkin calculations accounting for how long it takes for a signal to traverse the ears, nerves, and muscles, and concluded that start times faster than 0.1 second are possible.

“I’m sure that you can react in less than 100 milliseconds,” Milloz says, noting he’s recorded it himself in unpublished work. Yet he doesn’t know what the exact number ought to be.

There’s no “gold standard” for studying race starts

World Athletics has maintained that the 0.1 second rule is based on “the science on standard reaction times.”

Other sources disagree. Sports historian PJ Vazel, who wrote a report on the history of reaction time for the IAAF (the former name of World Athletics), says this rule actually dates back to the 1960s, and a West German sprinter named Armin Hary.

Hary was known as the “Thief of Starts,” due to his suspiciously fast starting times in sprint races. It’s unclear whether Hary anticipated the gun, or just had a very fast reaction time (some tests indicated the latter was the case). “He was constantly starting faster than the others,” Vazel says. “There was controversy.” Enough so that West Germany pushed for an automated system to be built into starting blocks themselves to measure false starts.

West Germany worked with the watch company Junghans, which developed the blocks. According to their patent, the company says they performed tests which found that sprinters were not starting faster than 0.1 seconds. That limit became a rough rule of thumb for the next few decades, Vazel explains, until it was officially codified in 1989. “It’s unfortunate,” Vazel says, that people still think this rule was founded on a scientific basis. “It was not.”

Scientific — in the purest sense of the word — would mean allowing outside researchers to verify the findings in an open and consistent manner.

When Milloz says he doesn’t know what the limit is, it’s because “there is no gold standard,” he says, on how to study this. Small changes to the experimental setup — what type of sensors are used, how they are calibrated — can yield different answers.

Scientists aren’t even sure how, precisely, the official recording systems are calibrated. According to Milloz and colleagues writing in the journal Sports Medicine, “The precise details of event detection algorithms [i.e., how the starting blocks record a start] are not made public by SIS [start information system] manufacturers.”

On top of that, variables like how loud the sound of the gun is, and how long runners have to wait before the starting gun is fired can all influence their speed. (Both a louder gun, and a longer wait tend to result in faster starts.) Ideally, World Athletics and outside scientists could agree on how to control for all this.

Vazel says World Athletics needs to be more transparent around how the machines actually calculate their results. In fact, there is reason to believe that the sensors at the World Championships in Eugene may have been recording faster reaction times than normal.

Gaither wasn’t the only runner at the 2022 World Championships to be disqualified for starting after the gun. Julien Alfred was disqualified for starting 0.095 seconds after the gun, and Devon Allen was disqualified for starting 0.099 seconds after the gun, just one thousandth of a second too quickly.

We reached out to World Athletics about why the 0.1 second rule has not been changed when scientific studies have shown runners can react more quickly.

They stand by it. According to World Athletics, “The 100ms rule was initially set as it was determined to be the minimum auditory reaction time.”

We pointed out that World Athletics even commissioned its own study on reaction times in 2009, which determined that the limit should be lowered from 0.1 second.

When we asked why that didn’t prompt a change, World Athletics replied, “The Technical Committee felt that the study, which was carried out using only six non-elite athletes, was not sufficiently robust to warrant a change.”

So round and round we go. Scientists say there isn’t data to support keeping the 0.1 second rule. And here World Athletics is saying there isn’t data to throw it out either.

At least one World Athletics council member has called for a rule change. “It is standard procedure after each world championships for the World Athletics Competition Commission to review the championships and recommend any rule changes,” World Athletics told us in 2022.

Basically: They said they were looking into it. Since then, World Athletics has updated its rules, very slightly. Now, if there’s any doubt about the call from the automated sensors, referees can allow athletes to run and appeal afterwards. So enforcement is a little more flexible. But starting faster than a tenth of a second is still considered to be a false start.

Still, one thing seems clear: We don’t know how fast a runner can start, but it seems likely to be faster than 0.1 seconds.

What would a fairer race look like?

There’s some evidence that the 0.1 second limit and the strict rules surrounding it might be holding racers back from starting as fast as possible. Over the years, the costs of false starting have increased. It’s now the case that a single false start can get a runner disqualified from a race. As the rules have grown stricter, studies suggest racers have started more cautiously. One study found starts in international championships slowed down by 20 percent from 1997 to 2011.

So what’s the answer here? Milloz thinks the sport could benefit from more science and standardization. He would like to bring the top athletes in the world to a lab to test their fastest possible starts on machines and with methods that all stakeholders can agree are the “gold standard” for the sport and science. “Gather a lot of response times,” Milloz says. “And try to plot the distribution,” to more clearly see what time would be an unacceptable outlier.

But even then, there could still be some questions about the start of a race. Often in sports, the more you zoom into a moment with technology, the more complicated calls become. When you look more closely at starts, Milloz says, you’ll find the first parts of the body to move after the gun goes off are not the feet on the starting blocks, but the hands, pushing off the ground. Might it be fairer to record starts from the hands, and not the feet? Milloz says the hands can start moving 50 milliseconds before the feet.

Devon Allen is disqualified ahead of the men’s 100-meter hurdles final on day three of the World Athletics Championships in 2022.
Martin Rickett/PA Images via Getty Images

But why stop at the hands? Might a more perfect start detection system, in the future, actually tap into a racer’s brain to see when they first gave their body the motor command to run? Deciding how to record the start of a race comes with some choices to make about when and where it starts.

“There is no perfect way to record something,” Milloz says. Every estimate will come with some range of error, or with some careful choices to make. “There is always some limitation.”

Perhaps anticipating the gun could be a part of the sport. But from our reporting, this seems like an unpopular idea that would lead to more false starts, more race restarts, and messier races overall. Perhaps World Athletics could encourage officials to have more discretion to overrule the computerized start system when the margins are tiny. But then, with discretion, comes inconsistency.

Ultimately, even if a lower reaction time threshold is set — depending on where and how it’s set — it’s still possible someone could come along one day and break it.

Each choice here comes with a compromise.

The idea of perfect fairness in sports may simply be impossible. “There’s no way to make sports perfectly fair,” says sports writer Joe Posnanski. “What you want to do is make it fair enough that people have faith in it.”

At the very least, World Athletics can start by making the reaction time limit lower than 0.1 seconds. Given that race starts may always be a gray area, it may be impossible to prevent all false accusations of cheating. But hopefully it will at least be possible to lower the number of athletes unfairly disqualified.

Since the World Championships, Gaither’s false start has weighed on her. “I’ve kind of been experiencing a little PTSD with it,” she says, calling the incident embarrassing. “Now, when I get to my blocks, the only thing that I’m thinking about in my blocks is ‘be patient.’ That’s literally the thing that’s been engraved in my head since that moment. Be patient because you can’t afford for that to happen again.”

We told Gaither a synopsis of our reporting: That it’s scientifically plausible she started that quickly. “I really appreciate that,” she says.

“Our sport,” she says, “is nowhere near perfect.” But loving it means wanting to see it get better. ”I’m one of the true lovers of this sport,” she says. “And, you know, as big of a blow as that was, it hasn’t changed.”

Update: August 23, 2023, 11:30 am ET: This story, originally published in September 2022, has been updated to include a slight change in the World Athletics rules on disqualifying athletes for starting too fast.


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