100-meter sprint world record could go as low as 9....( 2008 was a great summer for sports' ...)

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. He publishes his predictions for their top speeds on 28 November 2008 in The Journal of Experimental Biology at http://jeb.biologists.org.

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 17m/s.

For humans the results were complicated by the different distances that people race. Looking at the speeds of male race winners th
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