-anaerobic means without oxygen; glycolysis allows cells to generate ATP when mitochondrial activity is limited by the oxygen supply
-a muscle cell shifts to anaerobic respiration when it can't get enough oxygen into the cell to breakdown all of the pyruvate that forms at the end of glycolysis
-this occurs during strenuous exercise; break down glucose to pyruvate faster than the circulatory system can deliver oxygen to the cell
-some of the pyruvate is then fermented to form lactic acid
-during strenuous activity lasting more than 30 or 40 seconds, anaerobic pathways supply most of the ATP for muscle contraction
-glycolysis supplies ATP at a rate that is 2.5 times faster than aerobic mitochondrial stages of cellular respiration
-activities such as soccer and tennis that involve short bursts of activity got a long period of time rely mostly on anaerobic pathways to make ATP