Beijing 2008: Men 100m race analysis

17 Aug 2008 Posted by
Bolt’s 9.69s. Analysis of speed during the world record. How fast did Bolt run?

Well, yesterday evening we posted on the incredible performance of Usain Bolt, who took the Olympic 100m title in 9.69 seconds, breaking his own world record by 0.03 seconds, despite the fact that he started celebrating about 20m from the finish!

It was a spectacular performance, which you can read about here.

The splits and speeds

However, for today, we have been sent the split times for each 10m interval from Bolt’s race (thank you to Seb and an anonymous poster!), which we’ve used to calculate average speed for each 10m interval. The graph is shown below. Then below that, you’ll find a table showing the times at each 10m marker.




According to these data, his peak speed was hit at 50m, and he then maintained this all the way to 80m, running at about 44 km/hour.

Note that this is the AVERAGE speed – there are reports (which I don’t fully believe) that he hit 48km/hour. I can’t see where this would have happened, because that would mean that either side of it, he must have run much slower, and the graph above gives no indication that he ran anything but a consistently fast pace. So I think it’s far more likely that this figure of about 44km/hour is the speed he hit. The “instantaneous” peak is subject to too much error, unless the data are specifically gathered, which I don’t think is the case here.

How does this compare to past values? Well, when Donovan Bailey of Canada ran 9.84 secs to win the 1996 Gold, he was clocked at 43.6 km/hour using a radar gun. A later statistical calculation suggested that Bailey hit 47.6 km/hour, but again, I think this is a little misleading, because the “error” in timing means that 0.5 seconds here or there can swing the “peak speed” by a great deal.

Therefore, I think the better measure is average speed over 10m intervals. I’m quite sure that people have run as fast as Bolt did before. The magic of this performance, however, is not so much in the spectacular top speed between 50m and 80m, but rather that Bolt could maintain his speed for so long.

Remember, a sprinter typically hits peak somewhere between 50 and 60m, but then slows progressively. Bolt’s huge victory was created thanks to his incredible 50m stint between 40m and 90m, where he never dropped below 42km/hour.

How much faster can he run?

That is the question flying around today. What if Bolt had not celebrated from 20m out? Could he have run 9.50 seconds? Thompson, who took silver, said he’d run 9.54 seconds. The data above suggest that this is probably a little too optimistic. Even if he had maintained his speed for the final 20m (which is unlikely – he’d probably have dropped off slightly), he would have run 0.09 seconds faster. This would give him a 9.60 second time, which is incredible. More likely, he’d have slowed anyway (as all sprinters do), so I’d guess that his celebrations probably denied him about 0.05s and a time of 9.64s.

However, unless he can find the time somewhere else – in the start perhaps (he was second slowest in reaction time) – he won’t run 9.50 seconds. Then again, Bolt is a young man, and he’s already shown incredible ability. Who knows what the next two years will bring?


This post is part of the following threads: News/Controversies, Olympics Games, Beijing 2008 – ongoing stories on this site. View the thread timelines for more context on this post.