You'll crack up if you carry on working like this.

你再这样干下去，身体会垮掉的。

Slot your foot (big toe up, pinky toe down) into the crack up to the arch of your foot, keeping your knee out to the side.

把你的脚尖（大脚趾在上，小指在下）楔入裂缝中去，直到你的足弓的部分，膝盖保持向外。

I kept a straight face as long as I could, but I finally had to crack up.

我尽量板着面孔，但最后还是控制不住失声大笑起来。

E. g. His jokes made her crack up.

他的笑话让她大笑不止。

He might crack up under the strain.

压力大的话，他可能会崩溃的。