Usain Bolt, the world’s fastest person, ran a 100-meter sprint at a speed of 37.57 kilometers per hour. 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. 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. One major factor that influences your ability to run fast is the structure of your body, including how your muscles work. 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. 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. 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. 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. 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. Physical ability isn’t just about muscle. Your brain plays an important role, too. 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. 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. 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. Words to Learn 相關詞匯 【巡航】xúnháng cruise travel smoothly at a moderate speed 【一大步】yīdàbù stride a long step 世界上跑得最快的人是尤塞恩?博爾特，他百米短跑的速度為每小時37.57公里。 對于人類而言，這個速度快得驚人。這大約相當于在社區或學校周邊區域開車的速度。坐在車里的人可能不覺得車跑得有多快，但對于人來說就大不一樣。世界上很少跑者能接近這個速度。 幾個原因可以解釋為什么有些人跑得非?？欤渌藙t跑得比較慢。來自父母的遺傳基因是一個因素，但怎樣跑和經驗也會有影響。 影響快速奔跑能力的一個主要因素是身體結構，包括肌肉是如何工作的。 人體有600多塊肌肉協同工作，讓你能向不同方向、以不同速度運動。這些肌肉由不同肌纖維群組成，主要有兩種類型：快肌纖維和慢肌纖維。 肌肉由不同類型的纖維群共同組成。例如，小腿由兩塊肌肉組成：一塊主要是快肌纖維 —— 腓腸肌，用于短跑和跳躍；另一塊主要是慢肌纖維 —— 比目魚肌，用于走路和慢跑。 快肌纖維較大，幫助身體快速移動并產生巨大的力量。短跑運動員往往有大量快肌纖維。然而，這種肌肉纖維類型很容易疲勞，限制了能以最高速度跑步的時長，只能跑完相對較短的距離。 慢肌纖維較小，幫助人以較慢的速度、更強的耐力跑步。長跑運動員和競技自行車手往往有大量這類肌肉。 人擁有不同種肌肉纖維 —— 快肌纖維和慢肌纖維 —— 的數量主要由基因決定，所以你將不得不使用你出生既定擁有的肌纖維。但是鍛煉可以幫助訓練這些肌肉。 身體能力不僅僅關乎于肌肉。大腦也扮演著重要角色。 骨骼肌由大腦控制 —— 你在行動前思考，然后執行動作。例如：步幅有多大、手臂如何擺動、腳如何接觸地面，甚至呼吸技巧，這些都可以控制。 可以學習使用最佳跑步技術。這包括正確的姿勢：身體挺直，步幅合理，讓腳落在身體下方而不是太靠前 —— 這樣會減慢速度。 還可以通過全身協調來改善跑步姿勢，讓手臂與腿部交替擺動，用腳尖跑步，并最大限度地延長雙腳離地的“飛行”時間。使用正確的跑步技術有助于肌肉產生更多力量并協同發力，有助于跑得更快。(chinadaily.com.cn) | 