Athletics sprint events begin with a sequence of events:
Gun goes off
Sound travels from gun to ear
ear registers sound, sends impulse to brain
brain processes sound, sends signal to start running.
signal is received by muscles; sprinter goes
Except for step 1, these events are loosely described as the
athlete's reaction time. Major meets conducted by the IAAF record
reaction times, and usually publish them on their web-site.
When athletics sprint events separate athletes and world records
by hundredths of a second, its worth appreciating the magnitude of
the start events and particularly to consider their impact on
The reaction time is the time is takes for the runner to respond
to the start signal and begin leaving the starting blocks. (see Omega and
Sport - Athletics for a good run-down of the sprint timing and
start rules). IAAF policies consider that there is a limit to how
fast a human can react to a start signal. As of 2002, if an athlete
left the blocks sooner than 100 mSec after the start signal, he was
deemed to have false-started. Some fans think this is wrong and
that any reaction after the gun should be allowed.
If the athletes ears are 2m from a speaker emitting the sound of
the gun, the sound will travel at approximately 330 m/sec and hence
not even arrive at his ears for 0.006 seconds. If the athlete's ear
is say 20m from a cap-pistol, the sound will take 0.061 seconds to
reach his ears. If you are sitting in the crowd, say 60 m from the
starter, the sound won't reach you until 0.182 seconds after the
gun. Most athletes will in fact be on their way by the time you
hear it. Because light travels at 300 x 106m/sec and
reaches you in 200 nanoseconds, you will see the athletes move
noticeably before you hear the gun (ignoring the small difference
in reaction time to visual and auditory stimuli that you are likely
Someone standing on the finish line, 100m away, won't hear the
gun until 0.303 seconds after the start. He might see a puff of
smoke from the starter's pistol just 0.270 seconds after the gun.
Hand-timers were trained to react to the smoke signal.
An athlete in Lane 8 is about 8.5 m from one in Lane 1. Sound
will take 0.026 seconds to reach lane 8. If the starter's gun was a
further 10m from lane 1, the delay would blow out to 0.052 seconds.
IAAF world championships since 1995, but not the 2000 Sydney
Olympics, have used silent guns to overcome this - the
"bang" of the gun is sounded only in the speakers behind each
starting block. You need to be careful comparing the peformance of
someone in the Sydney Olympics with those at recent World
Championship. Some of the difference in the second decimal digit
reported for Sydney races is measurement error. Same goes for
comparing recent races with pre-1995 results - up to 0.05 seconds
of the last decade's improvement in the 100m sprint record could be
attributable to more accurate timing rather than athlete's
Once the sound has reached the athletes ears, his brain has to
command muscles to respond. The conduction speed of signals in the
brain is about 100 m/sec, and in the central nervous system falls
to about 70 m/sec. Just getting the signal from the brain to the
feet could take 0.026 seconds (assuming you are 1.8 m tall). As
will be seen below, there is also a very
substantial delay in recognising the sound of the gun...
Best Reaction Times
The best athletes reaction times are usually in the range of 120
mSec (0.12 sec) to 160 mSec (see graphs below). Tim Montgomery improved that
to a near perfect 104 mSec - and came very very close to being
false-started. The only sprinter to get closer to perfection was
Surin Bruny - who managed a 101 mSec in a the 1999 WC 2nd
Burrell's 1991 world record began with a reaction time of just
117 mSec. In the same race, Carl Lewis reacted in a snail's-pace 166
mSec, probably because he'd deliberately slowed his start due to
having an earlier false-start posted against him (this put him at
risk of disqualification if he false-started again). Taking away
reaction time, Burrell covered the 100 metres in 9.783 seconds,
Lewis in 9.764. Lewis was actually the faster runner, but Burrell
was the better "gunner".
In Rome (1987) Carl Lewis' reaction time was 193 mSec for a 9.93
sec run. By Seoul 1988, it was 136 mSec for his 9.92 sec run
against Ben Johnsons' 9.79 (Johnson was disqualified for drug
positive test), in Tokyo (1991) it was 140 mSec for his World
Record 9.86 run. Lewis's 1991 run was 70 mS faster than his 1987
result, and 50 mSec of that improvement was the reduction in start
reaction time (source data:
Biomechanics and Movement Science listserver discussion response by
J R Mereika or see alsoMereika's page
10 metre split data - Men's 100m); the other 20 mSec could have
been wind or other climatic factors!
Not surprisingly, in the ten years since 1991, false-starts have
become de-rigeur in 100 m sprints. Athletes are prepared to gamble
on beating the gun. Given how much margin in 100m times can be
attributed to reaction time, erring on the side of a false-start is
a gamble worth taking.
In reaction to the problem of excessive false-starts, the IAAF
has modified the rules so that from Feb 2003, the second runner to
false-start will be disqualified (regardless of who it was that
first false-started. a rule similar to that now applying in
swimming) - see BBC report
"Sprint Rule Well Received" Jan 16 2003..
Getting a lucky-start, or psyching your opponents out of a
quick-start, can make all the difference it takes to get a world
record or olympic medal. But with the new rule, if someone
false-starts, the gun anticipators are likely to "pull-back" and
races could then be run in slower times.
For about 120 years, the accepted figures for mean simple
reaction times for college-age individuals have been about 190 ms
(0.19 sec) for light stimuli and about 160 ms for sound stimuli
(Galton, 1899; Fieandt et al., 1956; Welford, 1980; Brebner and
Elite 100 m sprinters are way above the mean in at least running
performance, but their mean reaction times are not much better
than the average. For example, in the July 12 2003 Rome Golden
League A & B Series 100m sprints, reaction times averaged 153
mS (standard deviation 28 mS) - the minimum was 110 mS, max was 242
mS; there was virtually no correlation between running time and
reaction time (r2=0.02).
Figure 1 - Reaction Time v's Sprint
If reaction time could be "trained for", there ought to be a
correlation between faster running times and reaction times (and
all points should lie close to the trendline in Fig 1 above).
Psychologists carrying out simple reaction time experiments use
very large repetitions because of the wide random variation in most
test subject's performance. If these are random and can not be
trained out - why not discount them from the overall running times
or agree that any times that come down to the second decimal place
are equivalent ?
2003 World Championship Dummy Spit
The 2003 IAAF World Championships in Paris saw American Jon
Drummond disqualified in his heat of the Men's 100m for leaving the
blocks in 0.053 seconds after the gun. Asafa Powell, who's 10.02
time in the heats was not bettered at any time during the Paris
event, broke slightly later in 0.086 seconds and was also DQ'd.
Drummmond put on a disgraceful performance lying down and refusing
to leave the track for nearly 20 minutes. He showed no respect for
his fellow athletes and the distraction he caused to them, as it
delayed the event for over an hour.
Drummond's disqualification produced some lively debates from
those eager to defend him and suggest the IAAF rule was wrong. An
excellent example of the debate was the Track & Field Forum's
Reaction Times discussion.
The October 2003 edition of Track & Field magazine published graphs of the
pressure plate readings from Drummond's heat (see
Pressure-Plate Readout for the Whole Field
Lane draw: 1. Uchenna Emedolu; 2. Ronald Pognon; 3. Dwight Thomas;
4. Jon Drummond; 5. Asafa Powell; 6. Patrick Johnson; 7. Nicholas
Macrozonaris; 8. Ato Boldon
Wavy blue line is the amount of pressure athlete is putting on
Horizontal lines represent degrees of pressure; cross the first
one up from the baseline and the false-start indicator goes off (units are
Yellow vertical line is the firing of the gun; red vertical line
indicates false-start signalled (axis ticks are 0.1 sec).
Graphs are courtesy of Seiko, suppliers of the timing for the 2003 WC.
Track & Field defends Drummond on the basis that he
had not begun his power drive before the 0.1 sec limit (and only just crosses the
detection threshold at 0.052 seconds). But if you look at the point each athlete has
zero pressure on the blocks (look at the trailing edge of the pressure graph),
Drummond is out before everyone except Powell (who was also disqualified for
The pressure graphs also put the reaction times in context. Each athlete takes around
0.3 seconds between the leading edge of his drive off the blocks, and the time he
is clear of the blocks. Getting out of the blocks takes the sprinter 30 times the
difference in the last two world records. There is much to be gained by getting
out earlier than the field, as Drummond appeared to do.
Notwithstanding that, there appears to be considerable latitude in the
IAAF rules relating to the false start mechanism - leaving much up to the IAAF officials as to
what it deems approved. This is discussed in detail
by rival manufacturer
FinishLynx in a
USTCA article. While the Seiko gear pulled Drummond up because he simply crossed
a 25 kg threshold, more sophisticated processing aimed at detecting an ongoing rising edge may
have let him go. If Drummond had honed his starts by training on more forgiving equipment, it
might explain some of his conviction in Paris that he had not false started.
Many track fans sympathetic to Drummond claimed the TV coverage didn't show any movement. But
NTSC TV images sample movement only 30 times per second - so each frame is 0.033 seconds apart.
The wobbles in Drummonds pressure plate have a period of around 0.12 seconds; the television
sampling rate is simply not high enough to measure Drummonds movement (while it is more
than the Nyquist sampling minimum, it's not a sufficient multiple of the Nyquist sampling
rate to provide a convincing indication - even if you stop-frame and analyse each frame).
Reaction Time Scatter Graph
For those having difficulty understanding the science in the
0.100 second false-start threshold, here is a scatter graph of the
reaction times of the finalists in the last four IAAF World
Championship events. The best straight line fit suggests a slight
relationship between reaction time and 100m sprint times, but the
correlation of 0.10 indicates the fit is very, very poor.
If reaction times could be trained for (and were significantly
better for sprinters than more ordinary folk), you'd see a much
stronger correlation (0.80 or more - a correlation of 1.00 is a
perfectly exact fit).
Figure 2 - World Champions Reaction Time v's Sprint Time
It is fairly clear that reaction times are mostly in a 0.13 to
There are other variations between the 4 World Championship
races that may have made the correlation slightly better than in
the Figure 1 event. For example, different degrees of wind
assistance and altitude. Any larger sample would be weakened by
this effect. There may also be more outliers due to injury in
larger sample sizes (assuming brain reaction processes aren't
likely to be injury or fatigue affected).
Figure 3 show the effects of including the WC semi-finals results
in the scatter diagram. With the larger sample, there is more
spread and poorer correlation in the trend line (0.05, half that of
the finals-only result).
Figure 3 - WC Final and Semi-Finalist Reaction Times
It is likely that in the semi-finals, the best athletes are
saving themselves for the final and aren't running flat out. That
probably accounts for the extra spread. But there is no reason to
think that their reaction times are unrepresentative of their
potential - unlike running through pain barriers or risking injury
from over-exertion, reacting quickly in a semi is unlikely to
diminish your performance in the next days final. Of course, if
there is some legal or marginally legal stimulant that might help
you get out quick, you might not want to take it for a semi and
would keep it in the kitbag til the final
I nearly said "Hi Kelli", but as Figure 6 below shows, she
looked like she did have narcolepsy on the blocks. Whatever she
took didn't have much affect on her start reaction.
Figure 4 below shows a cumulative distribution of the percentage
of sprinters having reaction times below particular values, using
the same data as Figure 5. The reaction time corresponding to 50%
is the average reaction time, and the idea of the graph is to show
the spread of the distribution. There is some clustering of values
at 0.12 and 0.13 reaction times, due to the results only being
reported to 2 decimal places.
Figure 4 - Cumulative Distribution of Reaction Time
Lastly, Figure 5 shows WC SF and F just for 2003.
Figure 5 - 2003 World Championship Mens 100m
Final and Semi Finals
The average reaction time is 0.156 (standard deviation 0.026),
compared to 0.145 for 1997-2003 (std dev 0.022). While the final
was the slowest since 1983, the start reaction times were still
pretty fly. The difference of 0.011 in the average could be partly
attributed to having truncation errors in the 1997. Hence the
closeness of the average reaction time suggests there hasn't been
any material slowing down in the start process due to the new false
In the last 4 WC SF & F, Frank Fredicks averages 0.12 for
two appearances, and Surin Bruny averages 0.132 for 5 appearances
(2 below 0.13, one being the 0.101 lowest legal reaction time),
Green gets two below 0.13 but averages 0.134 for 6 appearances,
Boldon averages 0.138 for 5 appearances (2 below 0.13); nobody gets
below 0.13 and makes more than 1 appearance in the list. The best
in this list - Fredericks - was one of those DQed in semis, and
next best Bruny couldn't repeat anything close to his best result.
Their average performances and spread of results suggest they were
anticipating - not trained to do it repeatably.
Most elite sprinters have a spread of 0.02 seconds or more in their
reaction times. That's about one part in 6, and twice the margin
between the last 2 world records. But elite sprinters 100m sprint times
rarely vary by more than 0.1 seconds in 10.1 - that's one part in
100. They are able to control their sprint time with 10 times the
relative error of the reaction time. If reaction time is a trained response,
why isn't it repeatable with less variance ? It obviously
includes some random errors and is not strongly controllable.
It looks quite unlikely that a reaction time less than 0.12
seconds is repeatable and hence the result of good training or a
freakish natural ability.
Auditory Evoked Potentials
There is substantial grounds that the 0.1 second rule is very
Auditory Evoked Potentials are the brainwaves that can
be measured to show how quickly subjects respond to sound stimulus
are Auditory Evoked Potentials) . After a sound stimulus, an
evoked potential from the inner ear has to travel to the brainstem
(10 to 15 mSec delay). Next, it can take up to 50 mSec to get
passed from the brainstem to the auditory cortex. The auditory
cortex then has to appreciate and respond to this. The "slow"
cortical auditory ERPs appear between 0.05 and 0.200 seconds later,
with a large N1 event occuring between 0.08 and 0.100 seconds after
the stimulus. It's unlikely that the sound event has been
recognised and discriminated from background noise or could be
acted upon until this N1 event (it still has to pass to the motor
cortex, then get distributed via the much slower Central Nervous
System to muscles).
Neurophysiologists agree that to "hear" the sound thus takes
around 80 to 100 mSec from the stimulus. The auditory ERP's are
very close to visual evoked potential (retina to cortex) which is
70-120 msec. Neurophysiologists report that female EP's are on
average about 10% faster than male's. There is possibly a
physiological basis for women to be sharper.
However, a quick look at the 2003 WC Womens 100m Semi-finals and
finals shows the average reaction time to be 0.158 sec (std dev
0.027) - not significantly different to the mens 0.156. Even though
the womens 100m times are nearly 800 mSec slower, they're not
losing anything at the start. If womens EP's are theoretically
faster, this is not getting translated into speed off the
Interestingly, there was virtually no correlation between
reaction time and sprint time (correlation r2=0.002).
Here is the scatter diagram:
Figure 6 - Womens 100m Sprint Reaction Times
2003 WC F & SF
All the meets discussed above have used silent gun starting. As
discussed in the
Did Sydney Blocks Rob Mo Greene Of Olympic Record? (Track &
Field newsletter), use of unsilenced guns in the 2000 Sydney
Olympics cost gun reactors up to 0.05 seconds - and rewarded the
gun anticipators by allowing them to play with a 0.05 larger margin
above the 0.100 threshold
If athletes were able to see and react to the gun smoke,
there might not have been this sound-delay disadvantage. But maybe
watching for smoke would need your head up in the wrong position for
a good start and defeats the end of getting away faster.
There are physical limits to how fast an athlete can react to the
starters' gun. While the official IAAF rules set a limit of 0.100
seconds, it's likely that anyone reacting in less than 0.120
seconds has anticipated the gun.
The new false start rules introduced in Jan 2003 have raised the
stakes for those who want to gamble on anticipating the gun. This
saw two high profile athletes watch the World Championship 100m
from the sidelines, after their disqualification under the new
Nevertheless, the reaction times, and the individual variations
in it, can easily swamp the margins by which the world record has
been improved in recent years. Timing methods used at the Sydney
2000 Olympics recorded events to 2 decimal places, but didn't match
the accuracy standards in use at IAAF world championship events.
The flaws may well have prevented Maurice Greene setting a world
record that would still stand at the end of 2003. At least at
Sydney 2000, the second decimal digit did not have the same
significance as at the world championship. And Greene lost a world
record to Montgomery's Sep 2002 wind and luck assisted 9.78
Perhaps its reasonable to question whether, more generally, the
second decimal digit ever does represent something that an athlete
has control over. When records get down to improving only the
second decimal digits (hundredths of a second), they are likely to
be largely a matter of luck or being able to persist long enough
until luck comes your way.
First published 21st September, 2002, Last Revised
Last Revision: vdeck modification