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Cori cycle. The Cori cycle (also known as the lactic acid cycle), named after its discoverers, Carl Ferdinand Cori and Gerty Cori, [1] is a metabolic pathway in which lactate, produced by anaerobic glycolysis in muscles, is transported to the liver and converted to glucose, which then returns to the muscles and is cyclically metabolized back to lactate.
In fact, under anaerobic conditions, muscles generate lactic acid so quickly that pH of the blood passing through the muscles will drop to around 7.2, which causes haemoglobin to begin releasing roughly 10% more oxygen. [2]
It was once believed that lactic acid build-up was the cause of muscle fatigue. [8] The assumption was lactic acid had a "pickling" effect on muscles, inhibiting their ability to contract. Though the impact of lactic acid on performance is now uncertain, it may assist or hinder muscle fatigue.
Lactic acid is used as a food preservative, curing agent, and flavoring agent. [51] It is an ingredient in processed foods and is used as a decontaminant during meat processing. [52] Lactic acid is produced commercially by fermentation of carbohydrates such as glucose, sucrose, or lactose, or by chemical synthesis. [51]
Lactic acid tends to accumulate in the muscles, which causes pain in the muscle and joint as well as fatigue. [13] It also creates a gradient which induces water to flow out of cells and increases blood pressure. [14] Research suggests that lactic acid may also play a role in lowering levels of potassium in the blood. [15]
The anaerobic glycolysis (lactic acid) system is dominant from about 10–30 seconds during a maximal effort. It produces 2 ATP molecules per glucose molecule, [3] or about 5% of glucose's energy potential (38 ATP molecules). [4] [5] The speed at which ATP is produced is about 100 times that of oxidative phosphorylation. [1]
Aerobic training will not increase lactic acid tolerance, however, it will increase the lactate threshold. [2] Anaerobic training will increase tolerance of the effects of lactic acid over time, allowing the muscles’ ability to work in the presence of increased lactic acid.
This lactic acid, particularly if in excess, moves out of the skeletal muscles and either diffuses into the systemic circulation or is transferred into skeletal muscles that do not have an excessive buildup of lactic acid. The transfer of lactic acid out and into human skeletal muscle has been thought to be mediated by the H +-coupled ...