In elite sprinting, you can be disqualified for being too fast. If an athlete reacts to the starting gun in less than 0.100 seconds, the timing system calls a false start, even if they never moved before the gun.
That rule is built on one idea. Humans supposedly cannot hear a sound and start moving in under 100 ms. But is that really true? Research on sprint starts says the answer is more complicated.
Curious how fast you react to sound? Try the free audio reaction time test and see your own number in milliseconds.
Key takeaways
- At top meets, a reaction under 0.100 seconds after the gun counts as a false start.
- Since 2010, one false start means instant disqualification.
- Devon Allen was disqualified at the 2022 World Championships with a reaction of 0.099 seconds.
- A 2007 study found some sprinters could react in under 100 ms in testing.
- Online tests add device delay, so home scores are much slower than sprint start times.
How the False Start Rule Works
At major championships, starting blocks contain sensors that measure the force from each foot. The system records when an athlete first pushes hard enough after the gun. That gap is their reaction time.
If the reaction time is under 0.100 seconds, the system signals a false start. The thinking is simple. Anyone that fast must have guessed the gun rather than reacted to it.
The penalty has become stricter over time. A false start once led to a warning for the whole field. Since 2010, the athlete who false starts is disqualified straight away.
The 0.099 Second Case
The most famous recent example came at the 2022 World Athletics Championships in Eugene, Oregon. In the final of the men's 110 m hurdles, American Devon Allen was disqualified for a reaction time of 0.099 seconds, one thousandth of a second under the limit.
According to an AP report, his reaction in the semifinal had been 0.101 seconds, just inside the rule. The case sparked a big debate about whether a fixed 100 ms limit is fair.
What the Research Says About the 100 ms Limit
A 2007 study by Pain and Hibbs in the Journal of Sports Sciences tested nine athletes doing sprint starts on instrumented blocks. Several athletes had average reaction times under 100 ms in at least one condition. About one in five starts in the first two conditions was under 100 ms.
The authors concluded that the physical part of an auditory reaction can be under 85 ms, and muscle activity can begin in under 60 ms. In other words, very fast legal reactions may be possible for some trained athletes.
A 2011 study in PLOS One looked at the fastest reactions of 425 sprinters at the 2008 Beijing Olympics. Men reacted faster on average than women. The authors argued that one force threshold for everyone may not treat men and women equally, and estimated it could let a woman false start by up to 21 ms without penalty.
| Source | What it looked at | Main finding |
|---|---|---|
| Pain and Hibbs (2007) | 9 athletes, instrumented starting blocks | Some starts under 100 ms |
| Lipps et al. (2011) | 425 sprinters, Beijing 2008 | Men faster, rule may favour women |
| 2022 World Championships | Devon Allen, 110 m hurdles final | Disqualified at 0.099 s |
Why Sprinters Start on a Sound
Races start with a gun or beep because people usually react faster to sound than to light. Sound signals reach the brain quickly, while visual signals need extra processing in the eye first.
Our guide to visual vs auditory reaction time explains the gap in detail. It is also why the start of a race is such a pure test of auditory reaction speed.
Test yourself Do 10 rounds of the audio reaction test, then 10 rounds of the visual reaction test. Compare your averages to see how much faster you react to sound.
How Your Reaction Compares
Do not expect to get near 100 ms at home. An online test adds delay from your speakers, your mouse and your screen, and you are clicking a button rather than pushing off blocks.
So expect your online score to be a good deal slower than a sprinter on instrumented blocks. A consistent score that is clearly faster than your visual result is a good sign. Check where you stand with our reaction time benchmarks.
Want to see how sprinters compare with other athletes? Read reaction time by sport and the fastest human reaction time.
Frequently Asked Questions
What reaction time is a false start in sprinting?
Why is the false start limit 0.1 seconds?
What happened to Devon Allen?
Can you get a second chance after a false start?
How fast is a normal reaction to sound?
The Bottom Line
The 0.100 second false start rule assumes no one can truly react to a gun faster than that. Research shows a few trained sprinters may get close or even below it, which is why the rule is still debated.
For the rest of us, the more useful question is how fast you react to sound. Take the free VoltReflex audio reaction test and find out.
VoltReflex results are for entertainment and self-benchmarking, not a medical diagnosis.
Sources
- Pain and Hibbs (2007), Sprint starts and the minimum auditory reaction time, Journal of Sports Sciences
- Lipps, Galecki and Ashton-Miller (2011), On the implications of a sex difference in the reaction times of sprinters at the Beijing Olympics, PLOS One
- Associated Press (2022), Explainer, was Devon Allen too fast for his own good