Wednesday, December 3, 2008

What's Your Limit?

From our resident biologist Todd:
Here is a news article about a new biomechanical study that will interest runners. It probes the potential biomechanical limits that athletes face for improvement in running. This is just a news blurb. The actual technical article is obtainable (for free I believe) at:

GO AS LOW AS 9.48s
2008 was a great summer for sports’ fans.
World records tumbled at the Beijing
Olympics. Usain Bolt shattered both the
100m and 200m world records, knocking
tenths of a second off each. People have
been getting faster and faster over the last
few decades, which made marathon runner
Mark Denny, from Stanford University,
wonder whether last century’s massive
increase in population could account for
these dramatic improvements. He also
wondered whether there are absolute limits
on running speeds and, if so, how close are
we to them? Suspecting that there are,
Denny decided to scrutinise the running
performances of humans and two other
famous racing species, dogs and
thoroughbred horses, to find how close
modern runners are to their species’ peak
performances (p. 3836).
Having found records dating back to the
1920s for dogs and the 19th century for
humans and thoroughbreds, Denny looked
to see whether there were any clear trends;
had any of the species’ performances
already levelled off? Plotting the annual top
running speeds for all three species over the
years, it was clear that racing horses and
dogs have already reached a plateau. There
has been no improvement in the
thoroughbred’s speed in the Kentucky
Derby since the 1940s and two other major
US races since the 1970s, while dogs’
performances also levelled out in the 1970s.
The increasing dog and thoroughbred
populations hadn’t improved the animals’
performances. However, ‘chance might still
turn up a faster animal,’ says Denny and he
predicts that thoroughbreds could improve
their top speeds by as much as 1% in the
2012m Kentucky Derby, eventually
peaking at a top speed of just over 17ms–1.
For humans the results were complicated by
the different distances that people race.
Looking at the speeds of male race winners
through the years, it seems as if men still
haven’t reached their top speeds at any
distance and Denny predicts that male 100m
sprinters could one day get the record down
to an incredible 9.48 s, running 0.23ms–1
faster than Usain Bolt’s current world record
of 9.69 s. Meanwhile, female sprinters’ top
annual speeds levelled off in the 1970s,
suggesting that any improvement in their
speed was not due to a population increase.
However, Denny suspects that female
sprinters have room for improvement too,
and predicts that they could eventually
knock more than 0.4 s of the current 100m
world record to cover the distance in 10.19 s.
Looking at marathon runners, Denny
predicts that males could cut the current
world record, held by Haile Gebrselassie,
by between 2min7s and 4min23s. And
when he calculates the top speed that a
human female marathon runner could
achieve, Denny suspects that women could
eventually cross the 42,195 m finishing line
in 2h12min41s. He adds that Paula
Radcliffe’s current world record of
2h15min25s is very close to his average
prediction for the maximum marathon
speed and suspects that female marathon
runners could be the first group to approach
his predictions and test whether they hold.
Denny is pleased to have shown that it is
possible to calculate the absolute limits to
speed of running animals ranging from
humans to thoroughbred horses. However,
he emphasises that we have no idea what
aspect of physiology restricts runners’
performances, and is keen to find out what
will prevent future gold medal winners
from breaking Denny’s Limits.
Denny, M. W. (2008). Limits to running speed in dogs,
horses and humans. J. Exp. Biol. 211, 3836-3849." Inside JEB

Limits to running speed in dogs, horses and humans

Mark W. Denny

Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA


Accepted 20 October 2008

Are there absolute limits to the speed at which animals can run? If so, how close are present-day individuals to these limits? I approach these questions by using three statistical models and data from competitive races to estimate maximum running speeds for greyhounds, thoroughbred horses and elite human athletes. In each case, an absolute speed limit is definable, and the current record approaches that predicted maximum. While all such extrapolations must be used cautiously, these data suggest that there are limits to the ability of either natural or artificial selection to produce ever faster dogs, horses and humans. Quantification of the limits to running speed may aid in formulating and testing models of locomotion.

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