A world-champion body builder has no more muscles than does a 90 pound weakling. So what makes him so strong？ What other qualities does he need？

一個健美運動員的世界冠軍，全身的肌肉并不比一個90磅（約82斤）的弱雞多。那是什麼使得他如此強壯呢？

Muscles are made of thousands of stringy fibers—a number that is fixed during childhood—which contract when doing work. Strength does not depend on the number of fibers but on the function of their thickness and how many of them contract simultaneously.

肌肉，由成千上萬的纖維構成，這些纖維在運動時會收縮，其數量在兒童時期是固定的。

力量，不是由纖維的數量決定的，而是由纖維的厚度以及做運動時有多少纖維能夠同時收縮。

Exercise actually damages the muscles. During the recovery stage, the muscle fibers increase in size. Exercise also trains more muscle fibers to work at one time. If a muscle is weak or untrained, for example, only about 10 percent of its fibers will contract, whereas up to 90 percent of the fibers in a weight lifter's bulky biceps will contract.

鍛煉實際上會損害肌肉。在恢複階段，肌肉纖維的大小會增加。鍛煉還可以訓練更多的肌肉纖維一起起作用。如果肌肉無力或未受過訓練，則肌肉中隻有10％的纖維會收縮，舉重運動員笨重的二頭肌中多達90％的纖維會一起收縮。

Aside from strength, two other ingredients go into making an athlete: fitness and endurance. Fitness is related to the condition of the heart. During exercises, there is an increase in the amount of blood returning to the heart from the muscles. A typical volume for a runner at rest is about 5 quarts a minutes, compared with 30 quarts during a vigorous trial. This greater volume means more work for the heart—a muscular balloon that expands and contracts to take in blood and squeeze it out. Like any other muscle, the heart enlarges and gets stronger with routine exercise.

除了力量之外，訓練一個運動員還需要考慮其他兩個因素：健身和耐力。

健身與心髒狀況有關。在鍛煉過程中，從肌肉回流到心髒的血液量增加。跑步者在休息時的典型體積為每分鐘5誇脫，劇烈運動時達到30誇脫。更大的體積意味着心髒更多的工作量——膨脹和收縮的肌肉氣球會吸收血液并将其擠出，像任何其他肌肉一樣，心髒通過規律鍛煉來變得更強。

Endurance, or the length of time muscles can work, depends in part on how much fuel—in this case sugar—the muscles can store. A muscle that is continually exercised until it is exhausted of sugar tends to store more when it refuels at the next meal. And more sugar can translate into greater endurance the next time the muscle is put to the test.

耐力，或肌肉可以工作的時間長度，部分取決于肌肉可以存儲多少燃料（在這種情況下為糖分，肌肉可以儲存糖分的多少）。持續鍛煉直到糖耗盡的肌肉在下一餐加油時往往會儲存更多的糖，下次進行肌肉測試時，更多的糖可以轉化為更大的耐力。

#英語四六級必過#總結，增肌也好，強身也好，規律鍛煉都是必要的，既使得你的心肌更強壯，又讓你更能散發荷爾蒙的迷人魅力。

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