首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
A、With an increase in he amount of blood. B、With more muscles. C、With vigorous trial. D、With routine exercise. DHow does the hea
A、With an increase in he amount of blood. B、With more muscles. C、With vigorous trial. D、With routine exercise. DHow does the hea
admin
2009-04-23
30
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 he 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 he 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://kaotiyun.com/show/aEpK777K
0
大学英语六级
相关试题推荐
Thescientistswantedtokeeppeople______aboutthebreakthroughintheirexperiment.
Somepeoplethink______abouttheirrightsthantheydoabouttheirresponsibilities.
Theholidaysarethemostwastefultimeoftheyear.Theamountofwasteproducedincreasesbymorethan25%fromThanksgivingt
LadiesandGentlemen,Welcometothecompany.MynameisPeterJohnson.I’mtheProductionManager.I’ll【B1】______today.I
Whenitcomestosuccessfuloverseasinvestmentsthatcanyieldhighprofits,thekeyiswhichcountryyoushouldputyourcapita
VisitorstoBritainarealwayscomplainingaboutEnglishfoodbecausetheyrarelygetachancetoeatit.Mostoftherestaurant
Youjustcan’tdoeverythingonyourownifyouwanttoremaincompetitiveandstronginmodernsociety.
Scientistsfindthathard-workingpeoplelivemuchlongerthanaveragemenandwomen.Careerwomenarehealthierthanhousewives
Allofthemareastonished,becausesuchathinghasnever(hear)______ofbefore.
Whywillthewomanbeoutoftheofficealldaytoday?Becausesheis______.
随机试题
对象专业化的优点不包括
一女性患者,年龄39岁,因反复发作性腹痛、上腹部扪及肿块、皮肤轻度黄染来做超声检查,于右上腹部可见一9cm×6cm囊性肿块,边界清晰,其内透声良好。影像学检查需要与之鉴别的疾病有
下列关于孕妇感染弓形虫的描述正确的是
下列哪个选项的说法符合法律规定的政府采购原则?( )
关于工程分析方法中的类比分析法,下列说法正确的是( )。
1931年,日本侵略者制造了柳条湖事件,却反诬中国军队破坏铁路,并以此为借口,进攻中国东北军驻地大营,炮轰沈阳城,史称()事变。
试述法律行为的主要特征及其重要意义。
Thethreementriedmanytimestosneakacrosstheborderintotheneighbouringcountry,__________bythepoliceeachtime.
Whatisthewoman’smainproblem?
Theplaceofthechildinsocietyhasvariedforthousandsofyearsandhasbeeneffectedbydifferentculturesandreligions,
最新回复
(
0
)