1.Have you ever wondered why children always seem to have bags of energy and never run out of steam?
run out of steam 精疲力竭;失去势头
I'm afraid I can't climb to the top, I've run out of steam.
我恐怕爬不到顶了,我已经没力气了 。
2.Researchers have discovered that children have the stamina and levels of recovery of endurance athletes.
stamina 精力;毅力
You have to have a lot of stamina to be a top-class dancer.
你得很有毅力才能成为一名顶级舞蹈家 。