For example, during intense exercise, muscle cells will use up all of their oxygen and switch to a process called lactic acid fermentation, which uses glucose to produce energy.

举个例子，在激烈运动的过程中，肌肉细胞会耗尽它们的氧气并且转换到一个叫乳酸发酵的过程，就是用葡萄糖提供能量。