What happens when your muscles cells run out of oxygen?

Cells that do not require oxygen go through anaerobic respiration, which is a form of cellular respiration that uses fermentation to turn energy into useful energy. There are two types of anaerobic respiration, lactic acid fermentation and alcohol fermentation. Muscle cells do this when they run out of oxygen and go through fermentation instead. The product of this type of fermentation from muscle cells is lactic acid. Lactic acid is toxic and causes soreness and fatigue. Anybody who has been sore after exercise has experienced lactic acid fermentation.