原标题：How do some people run so fast? The science of speed explained
Usain Bolt, the world's fastest person, ran a 100-meter sprint at a speed of 23.35 miles per hour (37.57 kilometers per hour).
世界上跑得最快的人是尤塞恩·博尔特，他百米短跑的速度为每小时23.35英里（37.57公里）。
That's mind-blowingly fast for a human. It's about the same speed as cruising in a car through your neighborhood or in a school zone. It might not seem that fast when you're in the car, but for a person? Few runners in the world can even come close.
对于人类而言，这个速度真是快得惊人。这大约相当于在社区或学校周边区域开车的速度。当你坐在车里时，可能不觉得车跑得有多快，但对于一个人来说就不同了。世界上很少有跑步者能接近这个速度。
There are several reasons why some people can run very fast while others tend to run more slowly. Genetics – the traits you inherit from your parents – play a role, but so do your choices and experiences.
有几个原因可以解释为什么有些人能跑得非常快，而其他人则跑得比较慢。来自父母的遗传基因是一个因素，但你的个人选择和经历也会产生影响。
One major factor that influences your ability to run fast is the structure of your body, including how your muscles work.
影响你快速奔跑能力的一个主要因素是你的身体结构，包括你的肌肉是如何工作的。
The human body has more than 600 muscles that work together, allowing you to move in different directions and at various speeds. These muscles are made up of groups of fibers. There are two main types: fast twitch and slow twitch.
人体有600多块肌肉协同工作，让你能够向不同的方向移动，并以不同的速度移动。这些肌肉由纤维群组成。纤维群主要有两种类型：快肌纤维和慢肌纤维。
Muscles have different mixes of these fiber types. For example, two muscles make up the calf: One is predominantly fast twitch – that's the gastrocnemius, used for sprinting and jumping. The other is mostly slow twitch – that's the soleus, used for walking and jogging.
肌肉由不同类型的纤维群混合组成。例如，小腿由两块肌肉组成：一块主要是快肌纤维——那是腓肠肌，用于短跑和跳跃。另一块主要是慢肌纤维——那是比目鱼肌，用于走路和慢跑。
Fast-twitch muscle fibers are larger and help your body move quickly and generate significant force. Sprinters tend to have an abundance of fast-twitch muscle fibers. However, this muscle fiber type also tires quickly, which limits how long you can run at top speed to relatively short distances.
快肌纤维较大，帮助你的身体快速移动并产生巨大的力量。短跑运动员往往有大量的快肌纤维。然而，这种肌肉纤维类型也很容易疲劳，这限制了你以最高速度跑步的时间，只能维持相对较短的距离。
Slow-twitch muscle fibers are smaller and help you run at slower speeds, but with greater endurance. Long-distance runners and competitive cyclists tend to have a lot of these muscles.
慢肌纤维较小，帮助你以较慢的速度但更强的耐力跑步。长跑运动员和竞技自行车手往往有很多这种肌肉。
How much you have of each type of muscle fiber – fast twitch and slow twitch – is mostly determined by your genes, so you'll have to work with what you're born with when it comes to muscle types. But exercises can help train those muscles.
你拥有的每种肌肉纤维——快肌纤维和慢肌纤维——的数量主要由你的基因决定，所以在肌肉类型方面，你将不得不使用你出生时所拥有的肌肉纤维。但是锻炼可以帮助训练这些肌肉。
Physical ability isn't just about muscle. Your brain plays an important role, too.
身体能力不仅仅关乎于肌肉。你的大脑也扮演着重要的角色。
Your skeletal muscles are controlled by your brain – you think about your actions and then execute the movements. For example, you can control how long your stride is, how your arms move, how your feet hit the ground and even the techniques you use to breathe.
你的骨骼肌由大脑控制——你在行动前思考，然后执行动作。例如，你可以控制你的步幅有多大，你的手臂如何移动，你的脚如何接触地面，甚至你使用的呼吸技巧。
You can teach your body to use the best running techniques. That includes proper posture, so your body is standing tall, and an economical stride, so your feet land below you rather than too far out in front, where they can slow you down.
你可以教会你的身体使用最佳的跑步技术。这包括正确的姿势，让你的身体保持挺直，以及合理的步幅，让你的脚落在你的下方而不是太靠前，这样会减慢你的速度。
You can also improve your running form by using your whole body, with your arms pumping in opposition to the legs, running on your toes and maximizing the time spent in flight phase with both feet off the ground. Using proper running techniques helps the muscles create more force and work together, which helps you run faster.
你还可以通过动用全身上下来改善你的跑步姿势，让你的手臂与腿部交替摆动，用脚尖跑步，并最大限度地增加双脚离地的“飞行”时间。使用正确的跑步技术有助于肌肉产生更多的力量并协同发力，这有助于你跑得更快。
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