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:我又读了一遍《美国宪法》，上面写着：“人人生而平等。”事实并非如此!
 

Y:你想说什么？
 

D:成为奥运会的百米短跑冠军一直是我的梦想。可是，无论我多么努力，我就是跑不了那么快。
 

Y:你才意识到啊！
 

D:有些人就是比别人都跑得快。
 

Y:那是因为他们天生比他人多快收缩肌纤维。
 

D:有更多什么？
 

Y:快收缩肌纤维大大地决定了跑步速度。肌肉有两种纤维构成：快收缩肌肉纤维和慢收缩肌肉纤维。
 

D:有什么不同吗？
 

Y:慢收缩肌肉纤维用于有氧耗能，适合耐力性运动。
 

D: 所以慢收缩肌肉纤维收缩更慢，但是持续时间更长。
 

Y:说的对，因为马拉松耗能耗时长。
 

D:那么，短跑健将有很多快收缩肌肉纤维了。
 

Y:没错！慢收缩肌肉纤维富含肌红蛋白。肌红蛋白可帮助肌细胞将氧转运到线粒体，而线粒体是细胞能源工厂。
 

D:那么，马拉松选手肯定有很多慢收缩肌肉纤维了。
 

Y:对，快收缩肌肉纤维耗能快，特别适合短而有力的爆发性动作，比如短跑和跳跃，世界级短跑健将体内80%肌肉都是快收缩肌肉纤维。
 

D:真是幸福！
 

Y:当然，他们不仅仅靠天赋，还有艰苦地训练来完善技能。获得奥运金牌可并非肌肉纤维就可以。
 

D:但是不得不承认肌肉纤维起了作用。