首页
登录
职称英语
[originaltext] A world-champion body builder has no more muscles than does a
[originaltext] A world-champion body builder has no more muscles than does a
游客
2024-06-16
49
管理
问题
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 be need?
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.
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.
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.
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.
选项
A、With an increase in the amount of blood.
B、With more muscles.
C、With vigorous trial.
D、With routine exercise.
答案
D
解析
How does the heart enlarge and get stronger?
转载请注明原文地址:https://tihaiku.com/zcyy/3637171.html
相关试题推荐
[originaltext]M:MayIhelpyou?W:Yes,Iwouldliketoreturnthesetrousers.
[originaltext]M:MayIhelpyou?W:Yes,Iwouldliketoreturnthesetrousers.
[originaltext]M:MayIhelpyou?W:Yes,I’dliketosendthislettertomyfam
[originaltext]M:MayIhelpyou?W:Yes,I’dliketosendthislettertomyfam
[originaltext]W:Doesyourbrotherfeelanybettertoday?M:Heismuchbetter
[originaltext]M:Excuseme,Ithinkthere’samistakeinourbill.Wedidn’tha
[originaltext]M:Excuseme,Ithinkthere’samistakeinourbill.Wedidn’tha
[originaltext]A:Hi,Alice.It’snicetoseeyouagain.Iheardthatyouwentt
[originaltext]M:Wearebothfreethisafternoon.Shallwegosurfing?W:Gosu
[originaltext]M:Wearebothfreethisafternoon.Shallwegosurfing?W:Gosu
随机试题
Scientistswhobelievecellphonesaredangeroushavebeenthrowingouthypo
产生于20世纪30年代的中国现代文学作品包括( )。A.茅盾的《子夜》 B.
划分指的是把概念所反映的对象分为若干既不相交、也不遗漏的小类,来揭示这个概念所反
下列关于物权变动的表述中,不正确的是( )。A.动产物权设立和转让前,权利人已经
患者,女性,48岁,急性胆管炎、胆管结石术后,留置T管引流及腹腔引流管。T管引流
共用题干 第三篇TheBalancebetweenFluencyand
期货经营机构应当建立健全回访制度,由从事销售推介业务的人员进行回访。()
工程项目的安全预评价工作应在工程()阶段进行。A.施工 B.施工图预算
经调查,某水体有10个物种,每个物种个体数均为5,则该水体生物多样性状态是(
A.竞争性抑制 B.非竞争性抑制 C.反竞争性抑制 D.不可逆性抑制 E
最新回复
(
0
)