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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：

這位選手正蓄勢(shì)待發(fā)。

不到十秒鐘，跑速已從零提高到40公里每小時(shí)。這就是力量。

我是維爾斯博士。奧運(yùn)短跑選手是很獨(dú)特的運(yùn)動(dòng)員。為達(dá)到超人般的速度、贏得最后的勝利，他們重塑了肌肉。人體包含兩種肌肉纖維：慢縮肌纖維讓您在晨跑中保持耐力；而快縮肌纖維為您提供強(qiáng)大的瞬間力量。兩者在我們的體內(nèi)比例是相同的。但奧運(yùn)短跑選手的肌肉發(fā)生了轉(zhuǎn)化，其中80%的肌肉是快縮肌纖維?？炜s肌纖維消耗能量的速度比慢縮肌纖維快四倍。

奧運(yùn)短跑選手之所以能跑得如此之快的另一個(gè)原因在于神經(jīng)遞質(zhì)。遞質(zhì)在神經(jīng)突觸之間傳遞訊號(hào)，通知肌肉跑快一點(diǎn)。短跑選手通過(guò)訓(xùn)練增加神經(jīng)遞質(zhì)，將更多訊號(hào)傳送到肌肉。

選手還遭遇哪些挑戰(zhàn)呢？如何同時(shí)觸發(fā)所有的肌肉纖維，這十分關(guān)鍵。因?yàn)樵诎倜踪惻艿牟坏绞腌妰?nèi)，雙腳著地的時(shí)間不到四秒，他們大部分時(shí)間都在空中，簡(jiǎn)直是在賽道飛翔。肌肉如雷鳴，神經(jīng)如閃電。這些對(duì)于短跑運(yùn)動(dòng)員來(lái)說(shuō)是最重要的。

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