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英文字幕：

This athlete is getting ready to fly.

From zero to almost 40km/h in less than 10 seconds! THIS is power.

Hi, I'm Dr Greg Wells. Olympic sprinters are truly unique athletes. To win the sprint, they morph their muscles to attain superhuman speed. We all have two kinds of muscle fibres: Slow Twitch fibres give you endurance for that light morning jog. And Fast Twitch fibres give you short bursts of intense energy. You and I have equal amounts of both. But Olympic sprinters turn their muscles into 80% Fast Twitch fibres. Fast Twitch fibres burn energy four times quicker than Slow Twitch.

Here's another reason. Olympic sprinters can hit those speeds: Neurotransmitters. They shoot signals across nerve synapses, telling our muscles to run fast. Sprinters train their bodies to increase the number of neurotransmitters which then broadcast more signals to the muscle.

Another challenge for sprinters? To spark all those fibres at once. This is critical, because of the less than 10 seconds that it takes to run the 100 metres, they're only in contact with the ground for less than four! So for most of the race, they're soaring in mid-air...literally flying down the track! Muscle thunder...and nervous lightning. For Olympic sprinters, it's a perfect storm.

中文字幕：

这位选手正蓄势待发。

不到十秒钟，跑速已从零提高到40公里每小时。这就是力量。

我是维尔斯博士。奥运短跑选手是很独特的运动员。为达到超人般的速度、赢得最后的胜利，他们重塑了肌肉。人体包含两种肌肉纤维：慢缩肌纤维让您在晨跑中保持耐力；而快缩肌纤维为您提供强大的瞬间力量。两者在我们的体内比例是相同的。但奥运短跑选手的肌肉发生了转化，其中80%的肌肉是快缩肌纤维。快缩肌纤维消耗能量的速度比慢缩肌纤维快四倍。

奥运短跑选手之所以能跑得如此之快的另一个原因在于神经递质。递质在神经突触之间传递讯号，通知肌肉跑快一点。短跑选手通过训练增加神经递质，将更多讯号传送到肌肉。

选手还遭遇哪些挑战呢？如何同时触发所有的肌肉纤维，这十分关键。因为在百米赛跑的不到十秒钟内，双脚着地的时间不到四秒，他们大部分时间都在空中，简直是在赛道飞翔。肌肉如雷鸣，神经如闪电。这些对于短跑运动员来说是最重要的。

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（Video provided by GE 编辑：Julie）