Fast and Slow Twitch Muscle Fibers

http://sportsmedicine.about.com/od/anatomyandphysiology/a/MuscleFiberType.htm

Does muscle type determine sports ability?

By Elizabeth Quinn, About.com

Created: October 30, 2007

About.com Health's Disease and Condition content is reviewed by the Medical Review Board

Are you a better sprinter or distance runner? Many people believe thathaving more fast and slow twitch muscle fibers may determine whatsports athletes excel at and how they respond to training. Skeletal muscle is made up of bundles of individual muscle fiberscalled myocytes. Each myocyte contains many myofibrils, which arestrands of proteins (actin and myosin) that can grab on to each otherand pull. This shortens the muscle and causes muscle contraction.
It is generally accepted that muscle fiber types can be broken down into two main types: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers.  Fast twitch fibers can be further categorized into Type IIa and Type IIb fibers.
These distinctions seem to influence how muscles respond totraining and physical activity, and each fiber type is unique in itsability to contract in a certain way. Human muscles contain agenetically determined mixture of both slow and fast fiber types. Onaverage, we have about 50 percent slow twitch and 50 percent fasttwitch fibers in most of the muscles used for movement.

Slow Twitch (Type I)
The slow muscles are more efficient at using oxygen to generate morefuel (known as ATP) for continuous, extended muscle contractions over along time. They fire more slowly than fast twitch fibers and can go fora long time before they fatigue. Therefore, slow twitch fibers aregreat at helping athletes run marathons and bicycle for hours.
What Causes Muscle Fatigue?
Fast Twitch (Type II)
Because fast twitch fibers use anaerobicmetabolism to create fuel, they are much better at generating shortbursts of strength or speed than slow muscles. However, they fatiguemore quickly. Fast twitch fibers generally produce the same amount offorce per contraction as slow muscles, but they get their name becausethey are able to fire more rapidly. Having more fast twitch fibers canbe an asset to a sprinter since she needs to quickly generate a lot offorce.
Type IIa Fibers
These fast twitch muscle fibers are also known as intermediate fast-twitch fibers. They can use both aerobicandanaerobic metabolism almost equally to create energy. In this way, theyare a combination of Type I and Type II muscle fibers.
Type IIb Fibers
These fast twitch fibers useanaerobic metabolism to create energy and are the "classic" fast twitchmuscle fibers that excel at producing quick, powerful bursts of speed.This muscle fiber has the highest rate of contraction (rapid firing) ofall the muscle fiber types, but it also has a much faster rate offatigue and can't last as long before it needs rest.
Fiber Type and Performance
Our muscle fiber type may influence what sports we are naturally goodat or whether we are fast or strong. Olympic athletes tend to fall intosports that match their genetic makeup. Olympic sprinters have beenshown to possess about 80 percent fast twitch fibers, while those whoexcel in marathons tend to have 80 percent slow twitch fibers.
Are Athletes Born or Built?
Can Training Change Fiber Type?
This is not entirely understood, and research is still looking at thatquestion. There is some evidence showing that human skeletal muscle mayswitch fiber types from "fast" to "slow" due to training.
These studies and journal articles offer more insight on muscle fiber research:
High-Intensity Training and Changes in Muscle Fiber
Nature vs. Nurture: Can Exercise Really Alter Fiber Type Composition?
Effects of Endurance Training on Muscle Fiber
What can I do to improve my performance?
Keep in mind that genetic differences may be dramatic at the elite levels of athletic competition. But following the principles of conditioning can dramatically improve personal performance of a typical athlete.
With consistent endurance training, muscle fibers can developmore and improve their ability to cope with and adapt to the stress ofexercise.

Is fiber type the number one factor that makes an elite athlete elite?Fiber type is part of a great athlete's success, but it alone is a poorpredictor of performance. There are many other factors that go intodetermining athleticism, including mental preparedness, proper nutrition and hydration, getting enough rest, and having appropriate equipment and conditioning.

Sources:
Andersen, JL; Schjerling, P; Saltin, B. Scientific American. "Muscle, Genes and Athletic Performance" 9/2000. Page 49

McArdle, W.D., Katch, F.I. & Katch,V.L. (1996). Exercise physiology : Energy, nutrition and human performance

Lieber, R.L. (1992). Skeletal muscle structure and function :Implications for rehabilitation and sports medicine. Baltimore :Williams & Wilkins.

Andersen, JL; Schjerling, P; Saltin, B. Muscle, Genes and Athletic Performance. Scientific American. 9/2000

Thayer R, Collins J, Noble EG, Taylor AW. A decade of aerobic endurancetraining: histological evidence for fibre type transformation. Journalof Sports Medicine & Phys Fitness. 2000 Dec;40(4).

老A，你说中文吧，

我翻，我翻，我翻翻翻。
快，慢肌纤维
http://sportsmedicine.about.com/ ... MuscleFiberType.htm

是否肌肉类型确定运动能力？

由伊丽莎白奎恩， About.com

创建于： 07年10月30号

About.com健康的疾病和条件的内容进行审查医疗审查委员会

你是一个更好的短跑或长跑？许多人认为thathaving更加快速和慢速肌纤维可确定whatsports善于运动员以及他们如何应对培训。骨骼肌是由个别肌肉束fiberscalled细胞。每个细胞含有许多肌原纤维，其中arestrands蛋白质（肌动蛋白和肌球蛋白） ，可以吸引到每个otherand拉。这缩短了肌肉和肌肉收缩的原因。
人们普遍认为，肌纤维类型可分为两种主要类型：慢肌纤维（ I型）肌纤维和快肌纤维（ Ⅱ型）肌纤维。快缩纤维可进一步分为IIA和输入型防爆纤维。
这些区别似乎影响肌肉反应totraining和体力活动，每个纤维型的独特之处在于itsability合同以某种方式。人类的肌肉含有agenetically确定既慢速和快速纤维类型。 Onaverage ，我们有百分之五十左右缓慢抽搐和百分之五十fasttwitch纤维大部分用于肌肉运动。

慢颤搐（ I型）
缓慢，肌肉更有效地利用氧产生morefuel （称为三磷酸腺苷）的连续，延长肌肉收缩超过沿时间。他们火慢于快肌纤维和可以去论坛上很长一段时间，然后疲劳。因此，慢肌纤维aregreat帮助马拉松运动员和自行车运行了几个小时。
是什么原因导致肌肉疲劳？
快缩（ II型）
快肌纤维，因为使用anaerobicmetabolism建立燃料，他们创造更好的shortbursts的力量或速度慢的肌肉。然而，他们fatiguemore迅速。快缩纤维一般生产同样数量offorce每肌肉收缩慢，但他们得到他们的名字becausethey能够更迅速地火。有更多的快缩纤维canbe资产的短跑选手，因为她需要迅速产生大量offorce 。
第IIA型纤维
这些快缩肌纤维也称为中间快肌纤维。他们可以同时使用aerobicandanaerobic代谢几乎同样创造能源。通过这种方式， theyare结合I型和II型肌纤维。
型防爆纤维
这些快缩纤维useanaerobic创造能量代谢，是“典型的”快速twitchmuscle纤维，擅长生产快速，强大的扫射speed.This肌纤维的收缩率最高（快速射击） ofall的肌纤维类型，但它也有一个更快的速度offatigue并不能最后，只要在它需要休息。
纤维类型和性能
我们的肌纤维类型可能会影响什么运动我们当然goodat或者我们是否快速或强烈。奥运健儿往往属于intosports符合其基因构成。奥运短跑选手已beenshown拥有百分之八十快肌纤维，而那些whoexcel在马拉松往往有百分之八十慢肌纤维。
是运动员出生或内置？
可以训练变化纤维类型？
这是不完全理解和研究仍然希望在thatquestion 。有一些证据表明，人类骨骼肌纤维类型mayswitch由“快速” ，以“慢”由于训练。
这些研究和杂志文章提供了更深入的肌纤维的研究：
高强度的训练和肌纤维的变化
自然与培养：可以行使真正改变纤维类型组成？
耐力训练对肌纤维
我能做些什么来改善自己的表现？
请记住，遗传差异可能是戏剧性的精英层次的体育竞赛。但是，以下的原则，条件，就可以大幅度提高个人业绩的一个典型的运动员。
一致耐力训练，肌肉纤维可以developmore和改善他们有能力应付和适应压力ofexercise 。

是光纤的数量型的一个因素，可以使优秀运动员精英？纤维类型，是一个伟大的运动员的成功，但它仅仅是一个poorpredictor的性能。还有许多其他因素，去intodetermining运动，包括心理准备，适当的营养和水分，得到足够的休息，并在适当的设备和空调。

资料来源：
安徒生，巨浪; Schjerling ，磷; Saltin ， B.科学美国人。 “肌肉，基因和运动表现” 9 / 2000 。第49页

麦卡德尔， W.D. ， Katch ， F.I. ＆ Katch ， V.L. （ 1996年） 。运动生理学：能源，营养和人权的表现

利伯， R.L. （ 1992年） 。骨骼肌结构和功能：对恢复和运动医学。巴尔的摩：威廉姆斯和威尔金斯。

安徒生，巨浪; Schjerling ，磷; Saltin湾肌肉，基因和运动表现。科学美国人。 9 / 2000

塞耶研究，柯林斯J ，诺布尔乙二醇，泰勒左右。长达十年之久的有氧endurancetraining ：组织学证据纤维型转变。运动医学杂志及物理健身。 2000年12月， 40 （ 4 ） 。
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