Sunday, August 5, 2012

How Fast? Usain Bolt and Human Performance Limits

Today, Usain Bolt and a host of other lightning fast men will compete in the 100M run in the Olympics, seeking the titled of the "world's fastest man." How fast can a man run anyway? The Economist explores this question in this week's issue:
ON AUGUST 5th millions of people will watch the 100-metre final at the London Olympics. Many will wonder if anyone can repeat Usain Bolt’s feat in Berlin in 2009, when the Jamaican clocked 9.58 seconds, lopping 0.11 seconds—aeons in a sprint—off the previous world record, which he set at the 2008 Beijing games.

One person who thinks this unlikely is Mark Denny. Another 0.11 seconds would take the time below what Dr Denny, from Stanford University, reckons is the absolute limit of human athletic performance in the 100-metre dash.
In this section

In 2008 Dr Denny published a paper in which he crunched through the highest speeds achieved each year in running events from sprints to the marathon, some dating back to 1900 (see chart). A statistical technique called extreme-value analysis discerned trends and the maximum possible deviations from them. For the 100 metres, the human speed limit is 10.55 metres per second. This translates to 9.48 seconds.
Mark Denny's research can be found here, and he has this to day about Usain Bolt:
An excellent example of the potential for a continued increase in men's speeds is provided by the recent world records set in the 100 m and 200 m races by Usain Bolt of Jamaica. Over a span of 3 days in the Olympic games of 2008, Bolt `shattered' the then existing records, lowering the record in the 100 m from 9.72 to 9.69 s and in the 200 m from 19.32 to 19.30 s. Because Bolt is exceptionally tall for a sprinter (6′5″, 1.96 m), he was hailed by the press as a physical `freak' and the harbinger of a new era of sprinting. 

Should Bolt's records cast doubt on the predictions made here? The answer is no. Bolt's records are only small improvements on the existing records for the 100 m and 200 m races, 0.3% and 0.1%, respectively, and Bolt's records are not out of line with the logistic fit to the historical data (Figs 7 and 8, pink dots). Furthermore, there have previously been similar jumps in record speed. Thus, as admirable as they are, there is nothing in Bolt's records to suggest that the predictions made here are inaccurate or that human speeds in the 100 m and 200 m races are limitless.
Berthelot et al. looked at  the performances of 41,351 athletes competing in 70 Olympic track and firld (T&F) and swimming events. They conclude that limits are being reached in T&F but not yet in swimming.
The two studied disciplines show different progression schemes: most (63.9%) of T&F events have stopped progressing since 1993±8 years while all swimming events were progressing until 2009 (Fig. 1). This halt occurred 34 years earlier than the estimated stagnation of half of the WR in 5 Olympic disciplines [1]; it may reveal that most of T&F athletes are already beyond the edge of stagnation. Both genders present a slightly different evolution in T&F events, suggesting male events still have some potential reserve whereas the majority of women events (77.8%) has stopped progressing since 1992±8 years. Women may have reached their limits before men, despite a later entry into Olympic competition.
However, Berthelot et al. also expressed a view that the decision by FINA (swimming governing body) to ban the swim suits used by athletes in Beijing would see a regression of record breaking in swimming -- a prediction thoroughly refuted in London over last week.

Ultimately, the test of human progression in Olympic event record breaking will come not in academic journals, but on the track and in the pool. Nonetheless, the research reviewed here is highly suggestive that in many T&F events expectations of sustained record-breaking no longer square with the evidence. 
In another paper Bertheolt et al. conclude that human progression in Olympic record breaking has only one generation left in it, to 2027:
In summary, an epidemiological analysis of sport performances demonstrates that WR progression follows a piecewise exponential decaying pattern, altered by historical events. Results point out that in 2007, WR have reached 99% of their asymptotic value. Present conditions prevailing for the next 20 years, half of all WR won't be improved by more than 0.05%. As compared to the positivism triumphing at the time Coubertin inspired Olympic renewal, the present analysis emphasizes the ineluctable rarefaction of the quantifiable proofs of human physiological progression.
What will happen then?  Writing in The Boston Globe last year Paul Kix offered a sensible suggestion:
These ancient sports are a lot like the world’s current leading economies: stagnant, and looking for a way to break through. The best in both worlds do so by innovating, improving the available resources, and when that process exhausts itself, creating new ones.
We'll innovate. And if we can't "innovate" ourselves (at least not within the bounds of the rules), then we'll innovate the games. New events, new sports, new competitions will provide an infinite resources of frontiers to strive for and records to achieve. The end of competition is not risked by the reaching of human athletic performance.

Today, however, I'm hoping for a 9.47.


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