Energy Systems All movement requires energy. The methods by which the body generates energy are determined by the intensity and duration of the activity being undertaken. Activities that require short bursts of effort such as sprinting or jumping, require the body to produce large amounts of energy over a short period, whereas activities like marathon running or endurance cycling require continued energy over a longer period and at a slower rate. It is the energy systems of your body that facilitate these processes.

Energy Systems Energy is required in order to make the muscle fibres contract. This energy is obtained from foods in our diet, especially carbohydrate and fat. When these substances are burned in the muscles, ATP is formed, which is rich in energy. When ATP is broken down, it gives energy for muscle contraction. It is the contraction of muscle fibres and can be made in three ways: the creatine phosphate energy system, the lactic acid energy system and the aerobic energy system.

Creatine Phosphate Energy System ATP and creatine phosphate (or phosphocreatine, or PCr) make up the ATP- PCr system. It is the immediate energy system. Creatine phosphate (PCr) is a high energy compound. When exercise intensity is high, or energy needs to be instantaneous, creating phosphate shored in our muscles is broken down to provide energy to make ATP. ATP is the molecule which is the source of energy production. In this process, ATP is usually made without the presence of oxygen. Explosive work can be achieved, but only for short periods (up to 10 seconds) at maximum intensity. This is because the supply of PCr is very limited. ADP + creatine phosphate ATP + creatine

Anaerobic Glycolysis When the ATP- PCr begins to fade at around 10 seconds, the process of aerobic of glycolysis occurs. This system breaks down glycogen stores in the muscle and liver without the presence of oxygen. This produces lactic acid. This limits energy production via this process.

Lactic Acid Energy System Short term energy system. Meet energy requirements of higher intensity over a longer period (400m race) ATP can be made by partial breakdown of glucose and glycogen. It is an anaerobic process. Not sustainable over a long duration. Around seconds of maximal work is possible using this system. Glucose 2ATP + 2 lactic acid + heat Glycogen 3ATP + 2 lactic acid + heat

Lactic Acid Production This is the limiting factor of the anaerobic system. It accumulates and diffuses into the tissue fluid and the blood. If this substance is not removed by the circulatory system, it builds up. This causes fatigue.

Aerobic Energy System This is the long term energy system. If plenty of oxygen is available, glycogen and fatty acids break down to create large amounts of ATP. This produces carbon dioxide and water (does affect the muscles ability to contract). Aerobic energy production occurs in the mitochondria of the cells. These are the power stations of the cells. They are responsible for converting food into energy. The production of energy is slow- it takes a few minutes for the heart to deliver oxygenated blood to the working muscles. Long, continuous and moderate exercises produces energy using this system. Glucose + oxygen 38ATP + carbon dioxide + water + heat Fatty acids + oxygen 129 ATP + carbon dioxide + water + heat

Important note: ALL 3 ENERGY SYSTEMS OCCUR CONTINUOUSLY, BUT THE PROPORTION OF ENERGY PRODUCED BY EACH SYSTEM CHANGES AS THE EXERCISE CONTINUES. The intensity and duration of the activities is the main determining factor for which system is predominant. Energy Continuum

The way energy is provided for a 1500m race are very specific – “The ATP-PC is the predominant system for supplying energy during the 1 st 10 seconds, after which the lactic acid system becomes dominant for the next minute. The Aerobic System takes over for the middle of the race when the pace settles. There is then a return to the Lactic Acid system for the final sprint finish.” TASK: Analyse how the energy is provided for the activity you have been given Energy Continuum

Sport Creatine Phosphate Energy System Lactic acid energy system Aerobic energy system Archeryx Basketballxxx Hockeyxxx Netballxxx Soccerxxx Distance running xx x Jumpingx SprintingxX (depending on the event) Throwingx