Marathon Energy System

Task 2 – Describe (P3) or explain (M1) the concept of energy intake and expenditure in sports performance.

Brooks GA, Fahey TD, Baldwin KM (2005). Exercise Physiology: Human Bioenergetics and Its Application. 4th Edition

As stated before the three energy systems used by the body are the ATP-PC, anaerobic glycolysis and aerobic system. The ATP-PC and anaerobic glycolysis system (also known as lactic acid system) are anaerobicly based meaning that they don’t need a sufficient amount of oxygen to produce ATP. The aerobic system requires oxygen to produce ATP hence its name. All three system have fuels’ which produce energy. The ATP-PC uses phoso creatine and creatine phosphate, the lactic acid system uses glycogen and the aerobic system uses glycogen and triglycerides . Glycolysis refers to the breaking down of glycogen to from glucose which is used in ATP.

The energy systems used by the human body is categorised into the intensity of the activity performed and the time of which it takes to complete. In sports, she relationship between intensity and time is in most cases inversely proportional seen in the diagram. An example of a sport that is of high intensity and is completed in a short time period is a 100m sprint. In comparison an example of an activity or sport that is of low intensity but takes a long time to complete is a 3000m run.

One of the most significant reactions in Glycolysis is reaction one which involves the phosphorylation of glucose to form glucose-6-phosphate. Through the transfer of the hydrolysis of ATP, this supplies energy for the reaction and makes it essentially irreversible, having a negative free energy change, which allows for a spontaneous reaction in cells. Although the preparatory phase is energy consuming and uses up 2 ATP, the pay off phase synthesizes 4 molecules of ATP, with the transfer of 4e- via 2 hydride ions to 2 molecules of NAD+. Therefore, a net gain of 2 ATP is achieved through the glycolytic pathway alone. Following the glycolytic pathway, due to the absence of oxygen, as oxygen cannot be supplied fast enough to undergo aerobic respiration, the athlete will instead, undergo lactic acid fermentation. Lactic acid fermentation involves pyruvate that is formed from the glycolytic pathway to be reduced to lactate, with the aid of the enzyme, lactate dehydrogenase, while the coenzyme Nicotinamide Adenine Dinucleotide (NADH) is oxidised to NAD+. The product NAD+ then re-enters the glycolytic pathway in order to produce 2 ATP. This process of lactic acid fermentation produces 2 ATP for each cycle, and thus, rapidly supplies the body with a small amount of energy. However, with the buildup of lactic acid in the body, the athlete will eventually encounter the feeling of discomfort as this accumulation of lactate causes the body to

This energy is used to re-form the bonds between ADP and P to make ATP.

Our body produces energy called ATP. ATP is the renewable energy source for our cells that consists of 3 phosphates, a sugar and an adenine ring. ATP can be produced in two ways, through aerobic respiration or anaerobic respiration. Aerobic respiration occurs when there is oxygen, and anaerobic occurs when oxygen is not available. Also there are normally 3 phases in respiration, glycolysis, krebs cycle, and the electron transport chain. During glycolysis the glucose splits into two

oxidation in the mitochondria within each cell. Carbohydrates, proteins, and fats can all be metabolized as

For needed energy, a molecule of glucose is broken down through a process called glycolysis to form 2 ATP’s. The by-product is lactic acid. During intense, anaerobic muscle activity, anaerobic hydrolysis occurs. The Cori Cycle is activated to recycle the accumulated lactic acid back into useable energy. The lactic acid travels through the bloodstream to the oxygen-rich liver and is converted back to glucose by a process called gluconeogenesis. The glucose is then returned to the muscle to resupply it with energy. This conversion process uses up 6 ATP’s to make 2 ATP’s for the muscle to reuse. This creates a net loss of 4 ATP’s. The Cori cycle is meant to be a temporary shift of energy production from the oxygen-depleted muscles to the liver.

ATP-PC - Adenosine triphosphate (ATP) is the usable form of chemical energy for muscular activity. It is stored in most cells, particularly in muscle cells. Other forms of chemical energy, such as that available from the foods we eat, must be transferred into ATP form before they can be utilized by the muscle cells.

The anaerobic system known as the glycolytic pathway, uses glucose to produce ATP. Glucose is broken down into pyruvate through glycolysis to produce ATP. The amount of energy produced is very little, but you get the energy quickly. The glycolytic pathway is the second fastest way to resynthesize ATP and is the predominant energy system used for large bursts activities. Two exercises that utilize the glycolytic pathway are powerlifting such as bench press and deadlift.

Glycolysis is followed by the Krebs cycle, however, this stage does require oxygen and takes place in the mitochondria. During the Krebs cycle, pyuvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. This begins when pyruvic acid produced by glycolysis enters the mitochondria. As the cycle continues, citric acid is broken down into a 4-carbon molecule and more carbon dioxide is released. Then, high-energy electrons are passed to electron carriers and taken to the electron transport chain. All this produces 2 ATP, 6 NADH, 2 FADH, and 4 CO2 molecules.

Gradual progression of exercise time, frequency and intensity is recommended for best adherence and least injury risk.

Uniquely, glycolysis is both anaerobic and aerobic. The end product pyruvate, from glycolysis, is anabolized to lactic acid when there is a need for energy without an adequate supply of oxygen available. This last step or reaction enables glycolysis to continue producing ATP without the need for oxygen, which is why it is called the anaerobic energy system (Fink, 2009).

Three different metabolic energy systems power your workouts — and your day. Here’s how each one works, and how to make the most of them all.