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  • This episode of SciShow is sponsored by Blinkist.

  • Blinkist takes all the need-to-know info from thousands of nonfiction books and condenses

  • them into just fifteen minutes of content.

  • To learn more, click the link in the description.

  • {♫Intro♫}

  • In world-class running competitions, athletes just keep getting faster.

  • Like, Usain Boltwidely known as the world's fastest humanhas clocked in at nearly

  • forty-five kilometers per hour.

  • And that kind of makes you wonderhow much faster can we get?

  • Is there a limit here, or will someone eventually leave that record in the dust?

  • Well, no one can say for sure, but there is evidence a human speed limit should exist.

  • And not for the reasons you might think.

  • There are a ton of variables involved in running, from how fast you swing your legs to the type

  • of shoes you're wearing.

  • But, generally, there's one thing that seems to matter most at the professional level:

  • what happens when your feet are on the ground, during what's called the stance phase.

  • The fastest sprinters are the ones who can push off the track with the most force.

  • So you might think that the stronger their legs are, the more force they'll get out

  • of each step, and the faster they'll get.

  • Pretty simple, right?

  • Yeah, wellthere's more to it than that.

  • As you go faster, your feet actually spend less time on the ground during each step.

  • Like, when an Olympic-level sprinter is at top speed, their rubber meets the road for

  • less than 1/10 of a second.

  • So to run faster, they need to push harder in a vanishingly short window of time.

  • And that's where the trouble comes in.

  • See, when a muscle cell gets the signal to contract, it doesn't generate force right

  • away.

  • It starts off kind of slack.

  • So, before it can do anything to help you move, it needs to get nice and taut.

  • Then, it can start producing force.

  • The problem is, that process can only happen so fast.

  • And while some people do have faster muscle fibers than others, overall, it takes significantly

  • longer than one-tenth of a second for muscles produce their maximum force.

  • This means that, during a race, an athlete can't use all of their strength.

  • Their feet just aren't on the ground for long enough.

  • Sure, they can improve their technique, like by slamming their feet into the ground to

  • get rid of slack faster.

  • But even then, they'll reach a point where they can't improvewhere their muscle

  • fibers won't be able to provide more force during the tiny windows their feet are on

  • the ground.

  • When that happens, they've reached their speed limit and won't be able to go much faster.

  • Scientists think this limit exists because humans didn't evolve to be sprinting machines.

  • Instead, our leg muscles are optimized for multiple tasks, like standing, walking, and

  • running.

  • That means they need to be strong as well as fastand that strength comes at the

  • expense of a little extra speed.

  • Right now, it's hard to say exactly what the maximum human running speed is, especially

  • because some people have leg muscles that twitch a little faster than others.

  • But one 2010 study looked into it, and they suggest we probably can't get much faster

  • than about 50 km/h — even with genetic advantages, like extra speedy muscles.

  • Someday, if we did want to go faster than that, we'd likely have to turn to genetic

  • engineering or find a different gait that allowed our feet to stay on the ground for

  • longer.

  • That's actually why animals like cheetahs and greyhounds are so fast, even though they

  • have muscles with essentially the same limits as ours.

  • When they run, their feet stay on the ground for longer, so they have more time to push

  • off and generate force.

  • Unfortunately, galloping like a cheetahprobably isn't an option for us, since humans

  • evolved to run in a specific way.

  • But, hey.

  • If that 2010 study is right, it looks like we haven't hit our maximum speed yet.

  • So one way or another, it looks like someone could still beat Usain Bolt.

  • I'm no sprinter, but I can say that watching races is super exciting.

  • Events like the hundred-meter dash cram all sorts of action into only a few seconds!

  • And in a way, that's what the company Blinkist is trying to do with reading.

  • Blinkist is an app that takes all the best insights from nonfiction books and condenses

  • them into something you can read or listen to in about fifteen minutes.

  • For instance, they have a condensed version of Bill Bryson's A Short History of Nearly

  • Everything that you could probably read over your lunch break.

  • If you want to check it out or read one of Blinkist's thousands of other titles, you

  • can click the link in the description.

  • If you're one of the first 100 people to sign up there, you'll get free, unlimited

  • access to the site for seven days and 25% off if you decide to get a full membership.

  • You can also cancel any time during that trial period.

  • If you check them out, let us know what you think!

  • {♫Outro♫}

This episode of SciShow is sponsored by Blinkist.

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B1 中級

人が走れる最速のスピードとは? (What's the Fastest Speed a Person Could Run?)

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    林宜悉 に公開 2021 年 01 月 14 日
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