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英文字幕：

Swimming. A race for glory. A fight against physics.

Hi, I'm Dr Greg Wells. During a race, swimmers are battling more than just each other. The other opponent: water. A substance 800 times denser than air. It creates massive resistance, or drag. It's the swimmer's worst enemy.

Here's how they cut through it, and get maximum propulsion. To move themselves down the pool, Olympic swimmers don't just slice and pull straight back. They angle their hands and forearms to flow through the water and create lift. Basically, they turn their hands and forearms into propeller blades. So their shoulders get incredibly strong. They develop powerful rotator cuffs to control the shoulder and lats to transfer the power from the hands, through to the body.

Moving through the water at Olympic speed makes their muscles activate like crazy. This produces carbon dioxide, which is the body's exhaust. Muscles dump carbon dioxide into the blood, which turns the blood acidic. Our carotid arteries have chemoreceptors that sense if acids are building up. They send urgent warnings to the athlete's body: breathe, or suffer a meltdown. But Olympic swimmers can't breathe whenever they want. They can only inhale in time with the stroke, and they have to hold their breath when they push off the wall under water. So they train to desensitize their chemoreflexes and suppress the urge to breathe.

Slice through the drag...And make each breath count like it's your last. That's how you go from the pool, to the podium!

中文字幕：

游泳，爭取榮譽的比賽，對抗體能的爭斗。

我是維爾斯博士。游泳選手在比賽中不僅要對抗其他選手，還要對抗水。水的密度比空氣大800倍，能形成巨大的阻力或拉力，是選手最大的敵人。

選手是這樣切入水中，并獲得最大推動力。要在泳池中前進(jìn)，奧運選手不光是把水往后撥，他們把手和前臂以某角度穿入水中來制造浮力。基本上，他們把手和前臂變成螺旋槳，所以他們的肩膀異常強壯。他們練出強大的肩袖來控制肩膀和背闊肌，從而把力量從雙手傳到全身。

以奧運速度在水中前進(jìn)，需要他們的肌肉不停活動。這會排出二氧化碳，也就是身體的廢氣。肌肉把二氧化碳排進(jìn)血液，使血液變成酸性。頸動脈有化學(xué)感受體，可以感知酸的增加，于是便警告選手的身體：“快呼吸，不然身體會失靈”。但游泳選手不能隨意呼吸，他們只能配合劃水的動作吸氣，而且在水中推進(jìn)時要閉氣。因此他們通過訓(xùn)練，來鈍化化學(xué)感受體，壓抑呼吸的欲望。

切開水的拉力，把每下呼吸都當(dāng)成最后一口，這就是通往領(lǐng)獎臺之路。

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（Video provided by GE 編輯：Julie）