英語聽力文摘 “不平等”的肌肉
短跑“外星人”博爾特
Don:It’s not fair!
Yaël: What’s not fair?
D: I was rereading the Constitution of the United States. It says here that “All people are created equal.”That’s just not true!
Y:What do you mean?
D: Well, it’s always being my dream to become the Olympic champion in the 100-meter-dash. But no matter how hard I train, I’m just not fast enough.
Y:You just realize this now.
D:Some guys are simply faster than everyone else.
Y:That’s because some people are born with more faster twitch muscle fiber than others.
D:With what?
Y:That’s a big part of what make people faster than others. Muscles are made of two kinds of fibers–fast twitch and slow twitch.
D:What’s the difference?
Y:Slow-twitch fibers use energy aerobically and can work for long periods of time before getting tired.
D:So they can contract more slowly, but can keep going without burning themselves out.
Y:Right! Slow twitch fibers have a lot of myoglobin, a protein that helps transfer oxygen into the mitochondria, the power houses of the cell that produce cellular energy.
D:So Marathon runners must have a lot of slow twitch muscle fibers.
Y:Exactly, since they have to keep going for long periods.
D:So sprinters have a lot of fast twitch muscle fiber.
Y:Right! Fast twitch fibers consume energy quickly and are good for short, powerful bursts of movement like sprinting and jumping. World-class sprinters typically have about 80% fast twitch muscle fiber.
D:Luck dogs!
Y:And, of course, they train incredibly hard to develop their natural gifts. Olympic gold is not won by muscle fiber alone.
D:But it certainly helps!
Don:真不公平!
Yaël:什么不公平?
D:我又讀了一遍《美國憲法》，上面寫著：“人人生而平等。”事實(shí)并非如此!
Y:你想說什么?
D:成為奧運(yùn)會的百米短跑冠軍一直是我的夢想?？墒?，無論我多么努力，我就是跑不了那么快。
Y:你才意識到啊!
D:有些人就是比別人都跑得快。
Y:那是因?yàn)樗麄兲焐人硕嗫焓湛s肌纖維。
D:有更多什么?
Y:快收縮肌纖維大大地決定了跑步速度。肌肉有兩種纖維構(gòu)成：快收縮肌肉纖維和慢收縮肌肉纖維。
D:有什么不同嗎?
Y:慢收縮肌肉纖維用于有氧耗能，適合耐力性運(yùn)動。
D: 所以慢收縮肌肉纖維收縮更慢，但是持續(xù)時間更長。
Y:說的對，因?yàn)轳R拉松耗能耗時長。
D:那么，短跑健將有很多快收縮肌肉纖維了。
Y:沒錯!慢收縮肌肉纖維富含肌紅蛋白。肌紅蛋白可幫助肌細(xì)胞將氧轉(zhuǎn)運(yùn)到線粒體，而線粒體是細(xì)胞能源工廠。
D:那么，馬拉松選手肯定有很多慢收縮肌肉纖維了。
Y:對，快收縮肌肉纖維耗能快，特別適合短而有力的爆發(fā)性動作，比如短跑和跳躍，世界級短跑健將體內(nèi)80%肌肉都是快收縮肌肉纖維。
D:真是幸福!
Y:當(dāng)然，他們不僅僅靠天賦，還有艱苦地訓(xùn)練來完善技能。獲得奧運(yùn)金牌可并非肌肉纖維就可以。
D:但是不得不承認(rèn)肌肉纖維起了作用。
Constitution of the United States:《美國憲法》
dash：短跑
fiber:纖維
aerobical：有氧的
