How Fast Is Usain Bolt?

On the night of August 16, 2009, during the 100 meter final at the 2009 World Championships, Usain Bolt ran faster than any other human being has ever run before. He shattered his previous world record by more than a tenth of a second and, according to a statistical model of expected sprint times, set a pace not expected until roughly 2030. (Around the 60 meter mark, Bolt was going 27.78 miles per hour.) By any reasonable standard, it was one of the most impressive athletic achievements in modern sporting history. To watch Bolt in this race is to see a man literally leave his competitors behind. 

That, at least, is how it looks to the naked eye. However, according to a new study by Manuel Varlet and Michael Richardson, the singularity of Bolt’s performance is misleading. While it appears that Bolt was running by himself, paces ahead of everyone else, the scientists used a careful analysis of his stride to show that Bolt’s steps were actually synchronized with the steps of Tyson Gay, the American sprinter running just to his right. (Gay ran the race in 9.71 seconds, the third fastest time ever.) “These results demonstrate that even the most optimized and highly demanding individual motor skills can be modulated by the simple presence of other competitors through interpersonal synchronization processes,” write Varlet and Richardson. “This can happen without the awareness of the athletes nor that of millions of spectators.” In short, even when we’re trying outrun everyone, we can’t help but mirror the movements of someone else.

The scientists documented this synchronization using a frame-by-frame dissection of the two sprinters during the race. They found that, on roughly 28 percent of their steps, Bolt and Gay were in close sync, their strides aligned. Here’s what the data looks like, with the synchronized moments occurring around phase zero:

What makes this synchronization so surprising is that Bolt, because of his height, has an extremely long stride. As a result, it took him only 41 steps to reach the finish line; Gay required 45-46 steps. And yet, despite these innate physical differences, the sprinters often found themselves pounding the track at the exact same time.

It’s possible, of course, that this synchronization is random chance, an accidental side-effect of two men taking a lot of steps in a very short space. To rule out this possibility, Varlet and Richardson compared the strides of Bolt and Gay during their separate semifinal races. As expected, the runners exhibited far less synchronization when running apart, and shared a stride less than 10 percent of the time. (Similar results were achieved from a simulation of randomly generated phase distributions.)

So the synchronization of sprinters seems to be real. But does it matter? How did it impact the performance of Bolt and Gay? One possibility is that it slowed them down, interfering with the natural ease of their movements. Instead of sprinting the way they trained, Bolt and Gay might have warped their stride to fit the stride of someone else.

However, Varlet and Richardson conclude that syncing might have made the men faster, with the scientists citing a number of previous studies showing “that the stability and efficiency of gait behavior can be enhanced when entrained to external rhythms.” (The benefits of “external rhythms” might also explain the benefits of listening to pop music while exercising.) This suggests that having Bolt and Gay run side-by-side – each of them flanked by one of the few human beings capable of keeping pace  - improved their already near perfect form.

The moral of this clever study is that human synchronization is largely inescapable. As such, Varlet and Richardson’s analysis of two sprinters builds on a vast body of research documenting the ways in which subtle syncing influences almost all of our interactions. It doesn’t matter if we’re chatting with a stranger or kissing a lover or playing with a baby – our bodies are subtly blurred together, with pulse, breathing rate and blood pressure all converging on a similar state. The psychiatrists Thomas Lewis, Fari Amini and Richard Lannon refer to this process as “limbic resonance,” noting all the ways in which humans learn to synchronize their feelings and flesh with other people. (It's empathy in its most visceral form.) They argue that limbic resonance is especially important for the development of close relationships, and that if it weren’t for our ability to “bridge the gap between minds” we’d struggle to cope with stress or share our joys.

No man is an island. Not even the fastest man in the world.

Varlet, M., and M. J. Richardson. "What Would Be Usain Bolt's 100-Meter Sprint World Record Without Tyson Gay? Unintentional Interpersonal Synchronization Between the Two Sprinters." Journal of Experimental Psychology: Human perception and performance (2015).