肌肉断裂函数

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What allows people to run?
::是什么允许人们逃跑?

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. Muscle contractions allow movement , probably the most obvious function of muscles. What allows people to run long distances? Conditioned muscles help.
::肌肉收缩允许运动,也许是肌肉最明显的功能。什么可以使人们长途跋涉?

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Functions of Skeletal Muscle Contraction
::骨骼肌肉骨骼骨合体功能

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In addition to movement, contractions also fulfill three other important functions in the body: posture, joint stability, and heat production.
::除移动外,收缩还履行身体的另外三项重要职能:姿势、共同稳定和热能生产。

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• Joint stability refers to the support offered by various muscles and related tissues that surround a joint.
  ::联合稳定是指各种肌肉和紧绕联合体的相关组织所提供的支持。
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• Heat production by muscle tissue makes them an important part of the thermoregulatory mechanism of the body. Only about 40 percent of the energy input from ATP is converted into muscular work; the rest of the energy is converted to thermal energy (heat). For example, you shiver when you are cold because the moving (shivering) skeletal muscles generate heat that warms you up.
  ::肌肉组织产生的热量使其成为身体温度调节机制的一个重要部分。只有大约40%的ATP能量输入转化为肌肉工作;其余能量转换为热能(热能)。例如,冷时会颤抖,因为移动(抖动)骨骼肌肉产生热能,温暖你。
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• Posture, which is the arrangement of your body while sitting or standing, is maintained as a result of muscle contractions.
  ::姿势是身体在坐着或站着时的安排,因肌肉收缩而维持。

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Types of Muscle Contractions
::肌肉收缩类型

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Skeletal muscle contractions can be categorized as isometric or isotonic .
::骨骼肌肉收缩可归类为异度或同位素。

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An isometric contraction occurs when the muscle remains the same length despite building tension. Isometric exercises typically involve maximum contractions of a muscle by using one of the following:
::当肌肉尽管建筑紧张但仍保持同样的长度时,即发生等离子收缩。

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• The body's own muscles (e.g. pressing the palms together in front of the body).
  ::身体本身的肌肉(例如,在身体前按紧手掌)。
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• Structural items (e.g. pushing against a door frame).
  ::结构项目(例如按门框)。
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• Contracting a muscle against an opposing force such as a resistance band or gravity, as shown in  Figure .
  ::如图6所示,将肌肉绑在抵抗力或重力等对立力量上。

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An isotonic contraction occurs when tension in the muscle remains constant despite a change in muscle length. Lifting an object off a desk, walking, and running involve isotonic contractions. There are two types of isotonic contractions: concentric and eccentric. In a concentric contraction, the muscle shortens while generating force, such as in the shortening of the biceps brachii in your arm when you lift a glass to your mouth to take a drink or lift a set of dumbbells, as shown in Figure .
::肌肉的肌肉紧张状况在肌肉长度变化的情况下保持不变时会出现同位素收缩。 将物体从桌子上举起, 走路和跑动都涉及同位素收缩。 有两种同位素收缩类型: 同心收缩和异常收缩。 在同心收缩中,肌肉在产生力量时会缩短肌肉,例如,如图所示,将玻璃举到嘴边,喝一杯或举一捆哑铃时, 肌肉会缩短手臂的肌肉。

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During an eccentric contraction, the force opposing the contraction of the muscle is greater than the force that is produced by the muscle. Rather than working to pull a joint in the direction of the , the muscle acts to slow the movement at the joint. Eccentric contractions normally occur as a braking force, in opposition to a concentric contraction, to protect from damage. The muscle lengthens while generating force. Part of training for rapid movements, such as pitching during baseball, involves reducing eccentric braking, which allows greater power to be developed throughout the movement.
::在偏心收缩期间,反对肌肉收缩的力量大于肌肉产生的力量。肌肉收缩不是努力拉动联合点的方向,而是减缓联合点的动作。偏心收缩通常是一种制动力,与同心收缩相对立,目的是防止受损。肌肉拉长,同时产生力量。快速运动训练的一部分,如棒球期间的投球,涉及减少偏心制动,从而使得整个运动中能开发出更大的动力。

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Muscles and Exercise
::肌肉和运动

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As we learned earlier, your muscles are important for carrying out everyday activities, whether you are picking up a glass of orange juice, walking your dog, or snow wrestling ( Figure ). The ability of your body to carry out your daily activities without getting out of breath, sore, or overly tired is referred to as physical fitness . For example, a person who becomes breathless and tired after climbing a flight of stairs is not physically fit.
::正如我们早些时候学到的,你的肌肉对于开展日常活动很重要,无论你拿起一杯橙汁,走你的狗,还是雪地摔跤(图 ) 。 你的身体在不喘气、不痛或过度疲劳的情况下开展日常活动的能力被称为身体健康。 比如,一个人在爬上楼梯后变得喘不过气而疲劳,这在身体上是不合适的。

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We cannot discuss the effects of on your muscles without first clarifying the confusion between some common terms. It is easy to get confused with the relationship between “physical fitness,” “physical activity,” and “physical exercise.” Some people may think they cannot fit physical activity into their lives because they are unable to afford joining a gym, they do not have the time be involved in an organized sport, or they do not want to lift weights. However, physical activity encompasses so much more than just “working out.” Physical activity is any movement of the body that causes your muscles to contract and your heart rate to increase. Everyday activities such as carrying groceries, vacuuming, walking to class, or climbing a flight of stairs are physical activities.
::我们不能不首先澄清一些共同术语之间的混淆而讨论对你的肌肉的影响。 很容易与“身体健康”、“身体活动”和“身体锻炼”之间的关系混为一谈。 一些人可能认为他们无法将身体锻炼纳入生活中,因为他们负担不起参加健身房的费用,他们没有时间参与有组织的运动,或者他们不想提升体重。 然而,身体锻炼远远不止于“锻炼 ” 。 身体锻炼是身体的任何运动,导致身体肌肉收缩,心跳增加。 每天的活动,如搬运杂货、吸尘、上课、爬上楼梯等,都是体育活动。

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Being physically active for 60 minutes a day for at least five days a week helps a person maintain a good level of physical fitness and also helps him or her decrease their chance of developing diseases such as , Type 2 diabetes , and certain forms of . Varying levels of physical activity exist: from a sedentary lifestyle in which there is very little or no physical activity, to high-level athletic training. Most people will find themselves somewhere in the middle of this wide spectrum.
::每周至少5天、每天60分钟的体力活动有助于一个人保持良好的身体健康水平,也有助于他(她)降低发展2型糖尿病和某些形式糖尿病等疾病的可能性。

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Physical exercise is any activity that maintains or improves physical fitness and overall health. Exercise is often practiced to improve athletic ability or skill. Frequent and regular physical exercise is an important component in the prevention of some lifestyle diseases such as heart disease, cardiovascular disease, Type 2 diabetes, and obesity . Regular exercise is also helpful with reduction in or avoidance of symptoms of depression. Regular exercise improves both muscular strength and endurance. Muscular strength is the ability of the muscle to exert force during a contraction. Muscular endurance is the ability of the muscle to continue to contract over a period of time without getting fatigued. Regular stretching improves flexibility of the joints and helps avoid activity-related injuries.
::身体锻炼是保持或改善身体健康和整体健康的任何活动。锻炼通常是为了提高运动能力或技能。经常和定期的锻炼是预防某些生活方式疾病,如心脏病、心血管疾病、2型糖尿病和肥胖症的重要组成部分。定期锻炼也有助于减少或避免抑郁症状。定期锻炼既能提高肌肉强度,又能耐力。肌肉强度是肌肉在收缩期间施加力量的能力。肌肉耐力是肌肉在一段时间内继续减缩而不疲劳的能力。定期拉伸可以提高关节的灵活性,有助于避免与活动有关的伤害。

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Effect of Exercise on Muscles
::演习对肌肉的影响

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Exercises are generally grouped into three types depending on the overall effect they have on the :
::演习一般分为三类,取决于对下列活动的总体影响:

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• Aerobic , or endurance, exercises, such as cycling, walking, and running (see  Figure ), increase muscular endurance.
  ::有氧或耐力练习,如自行车、步行和跑步(见图),增加了肌肉耐力。
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• Anaerobic exercises, such as weight training (see Figure ) or sprinting, increase muscle strength.
  ::体重训练(见图)或冲刺等有氧锻炼会增加肌肉的强度。
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• Flexibility exercises, such as stretching, improve the range of motion of muscles and joints.
  ::伸展等灵活性练习,改善肌肉和关节的运动范围。

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Aerobic exercise causes several changes in skeletal muscle: increase in number, the fibers make more myoglobin, and more capillaries surround the fibers. These changes result in greater resistance to fatigue and more efficient metabolism . Aerobic exercise also benefits cardiac muscle . It results in the heart being able to pump a larger volume of with each beat due to an increase in the size of the heart’s ventricles .
::有氧锻炼导致骨骼肌肉的若干变化:数量增加,纤维产生更多的血红蛋白,而纤维周围的毛细膜增加。 这些变化导致对疲劳的抵抗力提高,新陈代谢效率提高。 有氧锻炼也有利于心脏肌肉。 由于心脏心血管的大小增加,心脏的心脏可以抽出更大的体积,每次抽动一次。

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Anaerobic, or resistance, exercises cause an increase in muscle mass. Muscles that are trained under anaerobic conditions develop differently, giving them greater performance in short-duration, high-intensity activities. As a result of repeated muscle contractions, muscle fibers develop a larger number of mitochondria and larger energy reserves.
::在厌氧条件下接受训练的肌肉发展得不同,在短期、高强度活动方面表现更好。 由于肌肉多次收缩,肌肉纤维发展出更多微粒和更大的能量储备。

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During anaerobic exercise, muscles break down stored creatine phosphate to generate ATP. Creatine phosphate is an important energy store in skeletal muscle. It is broken down to form creatine for the 2 to 7 seconds following intense contractions. After several seconds, further ATP energy is made available to muscles by breaking down the storage molecule glycogen into pyruvate through , as it normally does through the aerobic cycle. What differs is that pyruvate is fermented to lactic acid rather than broken down through the slower but more energy efficient aerobic process. Muscle glycogen is restored from blood sugar, which comes from the liver , from digested or amino acids that have been turned into glucose .
::在厌氧锻炼期间,肌肉分解储存的丙烯磷酸酯,以产生ATP。生物磷酸盐是骨骼肌肉中的一个重要能量储存库,在密集收缩后2至7秒形成。经过几秒钟后,通过将存储的分子甘油分解成凝聚物,如通常通过有氧循环的方式,进一步向肌肉提供亚硝酸酯的能量。不同的是,酸发酵,而不是通过较慢但更节能的氧气过程分解。肌肉甘油由血液糖恢复,而血液糖来自肝脏,来自消化或氨基酸,后者变成了葡萄糖。

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Two types of muscle fibers make up skeletal muscle:
::两种肌肉纤维构成骨骼肌肉:

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• Slow twitch muscle fibers, or "red" muscle, is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color. It can carry more oxygen and sustain aerobic activity. The endurance of slow twitch muscles is increased by aerobic training.
  ::缓慢抽动肌肉纤维,即“红”肌肉,与辣椒密合,并富含mitochondria 和 myoglobin,使肌肉组织具有其特有的红色,可以携带更多的氧气并保持有氧活动。慢抽动肌肉的耐力随着有氧训练而增加。
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• Fast twitch muscle fibers are the fastest type of muscle fibers in humans. These fibers tend to have fewer mitochondria than slow twitch fibers do, but they have larger energy stores. They can contract more quickly and with a greater amount of force than slow twitch fibers can. Fast twitch fibers can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful. Fast twitch muscle fibers become faster and stronger in response to short, intense activities such as weight training.
  ::快速抽动肌肉纤维是人类中最快的肌肉纤维类型。 这些纤维的米托孔蒂亚比慢抽动纤维少,但是它们拥有更大的能源储存。 它们可以更快地收缩,其强度也比慢抽动纤维大。 快速抽动纤维在肌肉萎缩前只能维持短时间的无氧活动爆发。 快速抽动肌肉纤维随着诸如体重训练等短、密集的活动而变得更快、更强。

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Both aerobic and anaerobic exercise also work to increase the mechanical efficiency of the heart by increasing cardiac volume (aerobic exercise) or myocardial thickness (strength training). Anaerobic training results in the thickening of the heart wall to push blood through arteries that are squeezed by increased muscular contractions.
::有氧和厌氧锻炼也有助于提高心脏的机械效率,增加心容量(有氧锻炼)或心心肌厚度(骨气训练),厌氧训练导致心脏壁厚,以通过肌肉收缩增加而挤压的动脉推进血液。

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Muscular Hypertrophy
::肌肉肥大

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Hypertrophy is the growth in size of muscle fibers and muscles, as shown in  Figure . Aerobic exercise does not tend to cause hypertrophy, even though the activity may go on for several hours. That is why long-distance runners tend to be slim, especially in the upper body. Hypertrophy is instead caused by high-intensity anaerobic exercises such as weight lifting or other exercises that cause the muscles to contract strongly against a resisting force. As a result of repeated muscle contractions, muscle fibers develop a larger number of mitochondria and larger energy reserves. The muscle fibers also develop more myofibrils, and each myofibril contains more actin and myosin filaments. The effect of this activity is hypertrophy of the stimulated muscle.
::如图所示,肌肉纤维和肌肉的体积的增长是肌肉纤维和肌肉体积的增长,如图所示。有氧锻炼不会造成肥大,即使活动可能持续数小时。这就是长距离的跑者往往瘦,特别是在上部,因此长距离的跑者往往是瘦的。而富营养化是由高密度的厌食性锻炼,例如举重或其他使肌肉与抵抗力量形成强烈抗力的其他锻炼造成的。由于肌肉的反复收缩,肌肉纤维会发展出更多的米托孔体和更大的能量储备。肌肉纤维还发展出更多的近足膜,而每个长距离的长距离的跑者都含有更多的动作和肌膜。这种活动的效果是刺激肌肉的富营养性。

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Factors such as age and sex can also affect muscle hypertrophy. During in males, hypertrophy occurs at an increased rate. In general, males are able to develop larger muscles because the male body produces far more testosterone than the female body does. On average, an adult human male body produces about eight to ten times more testosterone than an adult female body. Testosterone is an anabolic steroid, which means it increases within muscle fibers, resulting in the buildup of more myosin and actin filaments and myofibrils. More myofibrils means an increase in strength.
::年龄和性别等因素也会影响肌肉肥大。在雄性中,富营养化的发生速度加快。一般而言,雄性能够发展更大的肌肉,因为雄性身体的睾丸激素比雌性身体多得多。平均而言,成年男性身体的睾丸激素比成年女性身体多8至10倍。睾丸激素是一种新陈代谢类类类固醇,这意味着肌肉纤维内会增加,导致更多的近氧素和活性丝丝状和米洛菲布里尔的形成。更多的甲状腺素意味着体力的增强。

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Athletic heart syndrome is hypertrophy of cardiac muscle in response to exercise. A larger heart is able to pump more blood with a single beat, resulting in a lower resting pulse rate than average. The average resting heart rate for a healthy adult is between 60 and 100 beats per minute, but an athlete can have a resting pulse rate of 40 beats per minute or less! These changes would indicate heart-disease if observed in a person who is not active, but, in an athlete, a large heart with a slow resting pulse is the result of normal and healthy muscle growth and indicates a high level of fitness.
::心肌综合症是运动反应中心脏肌肉的肥大。较大的心脏能够用一跳抽出更多的血液,导致休息脉搏率低于平均水平。健康成年人的平均休息心率为每分钟60至100下,但运动员的休息脉搏率为每分钟40下或更小!这些变化表明,如果在不活跃的人身上观察到心脏疾病,但在运动员身上,休息脉搏缓慢的大心脏是正常和健康肌肉成长的结果,表明身体健康水平很高。

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Proper rest and recovery are also as important to health as exercise, otherwise the body is in a permanently injured state and will not improve or adapt well to the exercise. Therefore, it is important to remember to allow adequate recovery time for muscles between exercise sessions. This type of rest is called active rest.
::适当的休息和康复对健康也同锻炼一样重要,否则身体处于永久受伤状态,不会改善或适应这种锻炼,因此,必须记住在锻炼间隔期间给予肌肉足够的恢复时间,这种休息称为积极休息。

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Muscle Atrophy
::肌肉萎缩

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To remain healthy, muscles must be used. The condition in which muscle mass is lost is called atrophy. Atrophy can occur if muscles do not get enough exercise or if an injury, such as a fracture , causes immobility. Atrophy is the reverse of hypertrophy; muscle fibers become smaller, which causes the muscle to become smaller. Atrophy can also result from a spinal injury (CNS damage) leading to muscle paralysis, which the athlete in  Figure experiences. Diseases such as muscular dystrophy, amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease), and polio also cause muscle atrophy.
::为了保持健康,必须使用肌肉来保持健康。肌肉质量丧失的状态被称为萎缩。如果肌肉运动不够充分,或者受伤(如骨折)导致不动,就可能发生萎缩。萎缩是大营养的反向;肌肉纤维变小,导致肌肉变小。 脊椎损伤(CNS损伤)也会导致肌肉瘫痪,图中的运动员也经历过这种情况。 肌肉萎缩、萎缩性肺部硬化(ALS或Lou Gehrig病)和脊髓灰质炎等疾病也会导致肌肉萎缩。

  

 

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Summary
::摘要

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• There are two main types of muscle contraction: isometric contractions that do not involve a change in length, and isotonic contractions in which the muscle changes length.
  ::肌肉收缩主要有两种类型:不改变长度的等离子收缩和肌肉改变长度的同位素收缩。
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• Concentric contraction is the more familiar type of contraction, where the muscle shortens in length. Eccentric contraction refers to when the muscle contracts while lengthening (usually used as a braking mechanism).
  ::与心的收缩是比较熟悉的收缩类型,肌肉的收缩缩短了肌肉的长度。 与心的收缩是指肌肉在收缩的同时收缩(通常用作制动机制 ) 。
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• Aerobic exercise increases muscular endurance by increasing the blood supply to the muscle and the number of mitochondria.
  ::有氧锻炼增加肌肉耐力,增加肌肉的血液供应和米托乔翁德里亚的数量。
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• Anaerobic exercise increases muscular mass by increasing energy reserves and developing more myofibrils.
  ::通过增加能源储备和开发更多的近光膜,抗氧活动增加了肌肉质量。

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Review
::回顾

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1. What is the difference between physical activity and physical exercise?
   ::身体活动与身体锻炼有什么区别?
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2. What is the difference between slow and fast twitch muscles?
   ::慢动和快动肌肉有什么区别?
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3. What kind of exercise causes muscle hypertrophy?
   ::什么样的锻炼导致肌肉肥大?
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4. What is athletic heart syndrome?
   ::什么是运动心脏综合症?
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5. Provide possible scenarios where muscle atrophy might occur.
   ::提供可能发生肌肉萎缩的可能情况。