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C1HealthOct 27, 2026

Why doesn't your heart get tired like other muscles do?

心臓は他の筋肉のように、なぜ疲れないのでしょうか？

Veritasium10 videos Open on YouTube

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Translation

Have you ever wondered why your legs get tired but your heart never seems to?
脚は疲れるのに、心臓は疲れないのはなぜか、不思議に思ったことはありませんか？
Well, when you push your leg muscles to their limit, eventually they run out of oxygen, so they switch to a backup form of making energy called anaerobic metabolism.
脚の筋肉を限界まで使うと、やがて酸素が不足し、嫌気性代謝と呼ばれる予備のエネルギー生成方法に切り替わります。
It works, but it's far less efficient.
機能はしますが、効率ははるかに悪いのです。
It leads to changes in your muscles that ultimately cause aches and pain.
それは筋肉に変化をもたらし、最終的に痛みや疼きの原因となります。
Luckily, your heart works different.
幸い、心臓は仕組みが違います。
Its cells are packed with mitochondria, which are like tiny power plants that make energy using oxygen.
その細胞にはミトコンドリアがぎっしり詰まっており、それは酸素を使ってエネルギーを作る小さな発電所のようなものです。
Combined with a constant blood supply, they provide the tremendous amount of energy your heart needs to beat continuously.
絶え間ない血液供給と相まって、心臓が鼓動し続けるために必要な膨大なエネルギーを供給します。
No fatigue, no pain.
疲労も痛みもありません。
It even has its own built-in electrical pacemaker, so your brain doesn't need to tell it when to beat.
独自の電気的ペースメーカーまで備えているので、脳が鼓動のタイミングを指示する必要がありません。
Pretty neat.
なかなかすごいですね。
Over your lifetime, your heart will beat around three billion times without ever taking a break.
一生のうちに、心臓は休むことなく約30億回も鼓動します。
But that same design has a weakness.
しかし、その同じ仕組みには弱点があります。
Your leg muscles can cope with short periods of low oxygen.
脚の筋肉は、短時間の酸素不足には対処できます。
They get tired, but after a rest, they're good to go again.
疲れますが、休めばまた元通りになります。
But your heart doesn't have that luxury.
しかし心臓にはその余裕がありません。
If your heart's blood supply gets cut off, it can briefly switch to anaerobic metabolism.
心臓への血液供給が途絶えると、一時的に嫌気性代謝に切り替えることができます。
But after about 20 minutes, it runs out of fuel, and that can lead to irreversible damage.
しかし約20分後には燃料が尽き、不可逆的な損傷につながる可能性があります。
Bad news.
悪い知らせです。
So next time your legs are burning on a run, just be grateful they have the ability to recover.
だから次にランニングで脚が燃えるように痛くなったら、回復できる能力があることに感謝してください。

LingoDew, which teaches English through YouTube videos, measured this C1 video at 236 words per minute, faster than the C1 median of 186, and found 20% of its words outside the 1,000 most common in its English videos, fewer than the C1 median of 21%.

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