One disadvantage is that it is much less efficient than aerobic respiration regarding ATP production. It produces much less energy from the same amount of substrate and only makes 2 ATP per glucose molecule. Another disadvantage is that it produces lactic acid as a byproduct. The excess lactic acid can lead to muscle cramps and a decrease in blood pH. This is because following heavy exercise, the muscles and the liver must convert the lactic acid back to pyruvic acid.