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
2023-09-17
82
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/3020905.html
相关试题推荐
[originaltext]M:Hello,Mary.It’sJohn.[8]I’vegotsomethingtotellyouabou
[originaltext]M:Hello,Mary.It’sJohn.[8]I’vegotsomethingtotellyouabou
[originaltext]M:Jane,youseemtohaveworkedovertimeatyouroffice.W:Tha
[originaltext]M:Jane,youseemtohaveworkedovertimeatyouroffice.W:Tha
[originaltext]M:Jane,youseemtohaveworkedovertimeatyouroffice.W:Tha
Whatisthespeaker’smajor?Itis______.[br][originaltext]Iamacollege
Whatisthespeaker’smajor?Itis______.[br][originaltext]Iamacollege
Whatisthespeaker’smajor?Itis______.[originaltext]Iamacollegestude
[originaltext]M:[6]Whereareyougoingonholidaythisyear?W:Idon’tknowy
[originaltext]W:Hello,thisisNewYorkAirlines.WhatcanIdoforyou,sir?
随机试题
我喜欢两句诗:“山僧不解数甲子,一叶落知天下秋。”山上的和尚不知道如何计算里子,只观察自然,看到一片叶子落下,就知道已是秋天了。现代都市人正好相反,可以说是“落
Fiftyvolunteerswerealphabeticallydividedintotwoequalgroups,GroupA
国务院发布《风景名胜区管理暂行条例》的时间是()A.1980年 B.198
按照回收物品的渠道划分,逆向物流可分为退货逆向物流和( )。A.回收逆向物流
网络测试包括主动测试和被动测试,属于主动测试是(69)。A.使用ping命令
A.阳明经病 B.厥阴经病 C.太阳经病 D.少阴经病 E.少阳经病后头
2013年全国中高等学校研究生中,少数民族研究生所占比重约为:() A.5
救济原则是指公民、法人或者其他组织认为行政机关实施的行政许可使其合法权益受到损害
立卷类目是 a.案卷名册 b.移交目录 c.案卷目录
骨性牙颌面畸形是一种复杂的畸形,但不包括A.颅与颌 B.与颌 C.上颌与下颌
最新回复
(
0
)