Fathoming Bolt’s speed

Usain Bolt of Jamaica in familiar pose after victory in the men's 100m during the IAAF Diamond League Meeting Herculis in Monaco on Friday.

Usain Bolt of Jamaica in familiar pose after victory in the men's 100m during the IAAF Diamond League Meeting Herculis in Monaco on Friday.

Just why is Bolt so fast?

To answer this question, we must first understand what affects running speed.

At its most basic, speed is the product of stride-length and stride-frequency – in principle, the longer a sprinter’s stride and the more often it occurs, the faster the run.

Scientists and engineers have studied the two variables for a while now in a bid to discover why some athletes are quicker than others.

What they’ve realised is interesting. Running fast isn’t about how rapidly sprinters reposition their limbs in the air. It is about how hard their legs push on the ground.

Studies found that both swift runners and slow runners take roughly the same time when airborne to move their legs back into position for the next stride. What faster runners do better is apply a more powerful force to the ground through their foot – and, just as critically, do this in a briefer contact period.

As a recent story in the New York Times described it, “Sprinters cock the lead knee high and drive the foot into the track with a stiffened ankle… a punch delivered with high velocity and a sudden stop”.

Applying a strong force for a short instant does two things: it propels the athlete farther, appreciably increasing stride-length, and it reduces the duration of foot-ground contact, improving, to a lesser degree, stride-frequency. Speed, being a product of these two, naturally improves.

So how does all of this relate to Bolt?

The Jamaican is genetically gifted with explosive muscular power. He can generate an incredible amount of force (often in excess of 1000 pounds, or five times his body-weight) very quickly.

This derives from what are known as fast-twitch muscle fibres. These are prevalent in elite sprinters – and genuinely quick-bowlers. The ratio of fast-twitch to slow-twitch fibres in the average human body is about 50/50; in world-class speedsters, the ratio can be as high as 90/10.

Bolt, at 6’5”, is also unusually tall for a sprinter. World champions before him ranged from 5’9” to 6’3”, at the absolute maximum.

Generally, very tall sprinters are at a disadvantage because they can’t push hard enough against the ground to move the extra weight they carry. But the exceptional Bolt can – and his size therefore becomes a massive advantage. His stride-length is nearly 2.5m, on average 20cm longer than other elite sprinters. So while others take 44 to 50 steps to complete 100m, Bolt does it in just 41.

This combination of explosive power and a giant stride can get him to a top speed of 44.72kmph – only two others, Tyson Gay and Yohan Blake, have crossed the 44kmph barrier. But a 100m race isn’t just about who records the fastest speed, for this lasts for about 1.6 seconds. It is – strange as it sounds – about who slows down the slowest.

For, at high speeds over the course of 100m, fatigue sets in quick. No sprinter can accelerate for the full distance. But once Bolt reaches top speed at 60 to 70 meters, he maintains his velocity more efficiently than others, decelerating less.

There are three reasons why he bosses this part of the race.

One, he creates more force into the ground in less time than anyone else; for others to generate as much force, they would have to stay on the ground longer, which would slow them down.

Two, fatigue, some experts say, is a factor of number of strides – Bolt, as we saw, takes far fewer strides than others.

Three, he has an astonishingly repeatable technique. He is able to maintain his sprinting form under pressure when he’s tiring, something he has honed with super-coach Glen Mills. He doesn’t lose energy to an inefficient technique.

His fitness-work and training don’t always get the play his freakish physical skills do, but they’ve contributed immensely to his consistency.

So, the short answer to what makes Bolt so fast: everything. Stride-length, muscular power, speed-endurance, technique – he has it all.

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Printable version | Sep 9, 2022 3:56:35 pm |