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Introduction[edit | edit source]

Glycolysis is the metabolic process that serves as the foundation for both aerobic and anaerobic cellular respiration. Although it doesn't require oxygen (its purpose in anaerobic respiration) it is also the first step in cellular respiration.

Aerobic respiration summary.jpeg

  • The process entails the oxidation of glucose molecules, the single most crucial organic fuel in plants, microbes, and animals. Most cells prefer glucose.
  • In glycolysis, 2 ATP molecules are consumed, producing 4 ATP, 2 NADH, and 2 pyruvates per glucose molecule.[1]
  • The overall reaction of glycolysis which occurs in the cytoplasm[2]

Importance of Glycolysis[edit | edit source]

Glycolysis is important because it is the metabolic pathway through which glucose generates cellular energy. Glucose is the most important source of energy for all living organisms. In the human body, glucose is the preferred fuel for the vast majority of cells:

Cellular Respiration Direct[edit | edit source]

Mitochondria screen shot.png

Immediately upon finishing glycolysis, the cell must continue respiration in either an aerobic or anaerobic direction; this choice is made based on the circumstances of the particular cell.

  1. A cell that can perform aerobic respiration and which finds itself in the presence of oxygen will continue on to the aerobic citric acid cycle in the mitochondria.
  2. If a cell able to perform aerobic respiration is in a situation where there is no oxygen (such as muscles under extreme exertion), it will move into a type of anaerobic respiration called homolactic fermentation. [2]

Physiotherapy Exercise Implications[edit | edit source]

Glycogen structure.jpeg

Glycolysis is the breakdown of carbohydrates. It lasts from roughly ten seconds into physical activity up to about two to three minutes. The energy for glycolysis comes from glucose, or our stored form of glucose being glycogen.

Image R: Carbohydrate sources

  • The only macronutrient that can be synthesised into usable ATP under anaerobic conditions is carbohydrates.

We need to make sure we take in enough carbohydrates to keep our glycogen stores full.


A reduction in muscle glycogen is associated with fatigue.

  • Glycogen is stored in muscle tissue and the liver, and the average person holds about 1,500-2,000 calories of stored glycogen. Broken down there are about 100g of glycogen in the liver and upwards of 400g of stored glycogen in muscle tissue.
  • Regular anaerobic exercise increases your body's ability to store glycogen, giving you more energy during intense physical activity.
  • During endurance exercise, glycogen (an energy substrate for muscle contraction) is gradually depleted, making it difficult to continue exercising.

An effective way to improve endurance is to increase the glycogen stores in skeletal muscle and the liver before the commencement of exercise. eg it has been reported that glycogen stores can be increased by eating a low-carbohydrate diet for 3 days from 6 days prior to competition, followed by a high-carbohydrate diet for the next 3 days, resulting in the storage of 1.5 times more glycogen than normal.[4][5]


The anaerobic glycolysis system is the dominant energy system in the following examples:

Athletics, 200 m dash, 400 m dash, 800 m dash, 400 m hurdles, 4X400 m relay; Swimming, Freestyle swimming (50 m, 100 m, 4X100 m relay, Backstroke swimming (100 m), Breaststroke swimming (100 m), Medley swimming (4X100 m relay); Badminton; Canoe/Kayak, Slalom events (all events), Sprint, women`s events (all events); Badminton; Canoe/Kayak, Slalom events (all events), Sprint, women`s events (all events); Taekwondo; Tennis; Water polo; Wrestling.[6]

References[edit | edit source]

  1. Chaudhry R, Varacallo M. Biochemistry, glycolysis. Available: 3.12.2021)
  2. 2.0 2.1 Microbiology Glycolysis Explained in 10 Easy Steps Available: (accessed 3.12.2021)
  4. Aoi W, Naito Y, Yoshikawa T. Exercise and functional foods. Nutrition Journal. 2006 Dec;5(1):1-8.Available: (accessed 3.12.2021)
  5. breaking muscle Understanding Glycolysis: What It Is and How to Feed It Available: (accessed 3.12.2021)
  6. CAASN Anaerobic Glycolysis Available: 3.12.2021)