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
2023-09-16
65
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 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、The sources of strength.
B、Body building.
C、Strong heart.
D、Strength, fitness and endurance.
答案
A
解析
What does the passage mainly discuss?
转载请注明原文地址:http://tihaiku.com/zcyy/3019689.html
相关试题推荐
[originaltext]W:SweetHomeFurniture,canIhelpyou?M:Yes,[8]I’dliketob
[originaltext]W:SweetHomeFurniture,canIhelpyou?M:Yes,[8]I’dliketob
[originaltext]W:WhenareyouleavingforCambridge,Dr.Berle?M:OnWednesda
[originaltext]W:WhenareyouleavingforCambridge,Dr.Berle?M:OnWednesda
Atwhattimeofdaydidthefirestart?Intheearly______.[br][originaltext]
Atwhattimeofdaydidthefirestart?Intheearly______.[originaltext]No
[originaltext]W:Hello,AirChinaWhatcanIdoforyou,Sir?M:CanIbookat
[originaltext]W:Hello,AirChinaWhatcanIdoforyou,Sir?M:CanIbookat
[originaltext]W:Hi,Jack.Howwasyourweekend?M:Fine,[6]Iwentbacktomy
[originaltext]W:Hi,Jack.Howwasyourweekend?M:Fine,[6]Iwentbacktomy
随机试题
Thenewswasaterribleblowtoher,butshewill______theshocksoon.A、getout
That’s______.A、whereourdifferenceslieB、ourdifferencesliethereC、wheredo
Onlyunderspecialcircumstances______totakemake-uptests.A、freshmanareper
Britainwaswealthycountry,ahundredandfiftyyears【C1】______Therewere
伊曲康唑片处方中填充剂()A:淀粉 B:淀粉浆 C:羧甲基淀粉钠 D:硬
患者男,45岁,左股骨骨折固定术后,卧床第10天活动后突发胸闷、气促,伴胸痛,出
WAIS-CR的数字广度测验主要测量()多选A.短时记忆能力 B.计算力
下列关于货币资金循环中涉及到的业务表述正确的是( )。A.出纳员每日对库存现金进
混凝土实体检验的主要检验项目是()。A.混凝土强度 B.钢筋保护层厚度 C.
根据《劳动合同法》,下列情形中,用人单位不得与劳动者解除劳动合同的是()。
最新回复
(
0
)