The lactic acid energy system can be likened to a powerful SUV that emits plenty of smog. This energy system is fast and maintains good power, with limited endurance and a whole lot of waste product that hurts.
This system last 1-3min and produces ATP quickly, but uses a lot of carbohydrate (its fuel source) to do so. It is used for fast movement of high intensity, but produces plenty of acid in the process. As this acid is produced the body tries to remove it by converting it to lactate, but this process is not as fast as the acid production and when acid builds up it burns. It is the acidic build up of Hydrogen ions in the muscle that causes fatigue and slows the enzymes required for this system. Its by-product is technically pyruvic acid, but many textbooks say lactic acid. This system recovers as pyruvic acid is converted to lactate, and the lactate is taken to the liver where it is converted to glucose for further energy production. The rate of recovery is usually 30-60min.
The best sporting example to attach this to is 800m. The world record for which is 1:53:43 for women and 1:40:91 for men. This even really pushes the lactic acid system and causes large accumulations of pyruvic acid in muscle, giving that burning feeling. The lactic acid system provides enough ATP for the event to be run at higher intensities than the aerobic system. Athletes who have good abilities to remove lactate can use this system for longer.
