If our heart muscles never “get tired” even if they’re working hard, why aren’t the rest of our muscles the same way?

Question

I would imagine it would be a pretty good thing if we never tired out, even if it meant we weren’t quite as strong, or had to compromise elsewhere.

So why aren’t ALL our muscles the same way as the ones in our heart, where they’ll just keep working without aches, power loss or even all-out cramps and failure when they’re working hard?

Also, I do understand that even heart muscles can break down, e.g. in a heart attack, but we never get “heart cramps” even if we exercise all our other muscles to their limits and our heart is still working normally.

In: 42

Answer 1

Because the heart is very special, and very important, so it gets a *lot* of energy, second only to the brain. If every muscle in your body used that much energy, then our ancestors would have starved even more than they already did.

Plus, it requires incredible amounts of blood. Blood that is readily available at the heart, but less so literally anywhere else.