Anaerobic metabolism is the creation of ATP, the basic currency of energy, through the glycolysis of glucose from carbohydrates in the absence of oxygen. This occurs when your lungs cannot put enough oxygen into the bloodstream to keep up with the demands of your muscles for energy.
Anaerobic metabolism is less efficient than aerobic metabolism and produces just 2 ATP compared with up to 38 ATP for aerobic metabolism
It is generally only used for short bursts of activity, such as sprinting.
When there isn't enough oxygen in the bloodstream, glucose and glycogen cannot be fully broken down to carbon dioxide and water. Instead, lactic acid is produced, which can build up in the muscles and degrade muscle function.