The science of sprinting: How does Usain Bolt run so fast?

CTV News Channel: Does size matter? Professor Greg Wells explains whether height can make a difference when it comes to speed and sprinting.

At 5-foot-9, Canadian bronze-medal winning sprinter Andre De Grasse is hardly short. But at Sunday night’s 100-metre dash finals, he looked positively dwarfed by 6-foot-5 Usain Bolt of Jamaica, the gold-medal winner.

So is height important to sprinters and does it really make a difference when it comes to speed?

Not necessarily, says Dr. Greg Wells, an assistant professor in the Goldring Centre for High Performance Sport at the University of Toronto.

Wells says sprinting coaches don’t look for height when seeking out new recruits; what they are really looking for is an athlete’s ability to jump.

“You’re looking for someone who’s bouncy, someone who’s really explosive, someone who’s really powerful,” Wells told CTV News Channel Tuesday.

“People who can jump far and have that explosive ability tend to have Type 2 muscle fibres – the explosive muscle fibres.”

It’s a high proportion of those Type 2, fast-twitch fibres that make people such as de Grasse and Bolt such good sprinters. Those who have a higher proportion of Type 1, slow-twitch fibres on the other hand, tend to do better at endurance sports, such as marathons.

The average person has about a 50/50 distribution of Type 1 and Type 2 fibres, Wells says. But in world class sprinters, 90 per cent of their muscle fibres are of the Type 2 variety.

The finest sprinters also set themselves apart by learning to be efficient with their movements so they only propel themselves forward and don’t waste energy with sideways movements.

That’s important because although the race lasts less than 10 seconds, fatigue kicks in so quickly that most sprinters actually decelerate during the last few metres.

But what really sets Bolt apart from the pack at the 100-metre dash is his ability to be springy so that he barely touches the ground as he runs, Wells said.

“The interesting thing about Usain Bolt was that he took only 41 or 42 strides -- the number of times his feet actually touched the ground. De Grasse and some of the other competitors were all over 50. So he’s taking 20 per cent fewer strides than everybody else,” he said.

Because sprinters are almost flying down the track, Wells says their ability to push off explosively with each step is really what powers them along to the finish line.

At the elite level, world-class sprinters are actually in contact with the ground for less than three of the 9.8 seconds it takes them to get down the track.

“So in fact, if you’re really looking at it, the race is done in less than three seconds,” Wells said.