Food fuels and the three energy systemsText Reference1. Nelson Physical Education VCE Units 3&4 – Chapter 5.
Key Knowledge Characteristics and interplay of the three energy systems (ATP – CP, anaerobic glycolysis, aerobic system) for physical activity, including rate of ATP production, the capacity of each energy system and the contribution of each energy system. Fuels (both chemical and food) required for resynthesis of ATP during physical activity and the utilisation of food for energy. Relative contribution of the energy systems and fuels used to produce ATP in relation to the exercise intensity, duration and typeKey Skills Describe, using correct terminology, the interplay and relative contribution of the energy systems in different sporting Perform, observe, analyse and report on laboratory exercises designed to explore the relationship between the energy systems during physical activity Explain the role the energy systems play in enabling activities to occur as well as their contribution to active and passive recovery
1. Carbohydrates (CHO) – Preferred source of fuel during exercise (Glycogen)2. Fat – Concentrated fuel used during rest and Energy prolonged sub-maximal exercise.3. Protein – Used for growth and repair (Negligible use during exercise)
Everything we eat is broken downand either used immediately,excreted or stored as chemicalenergy
Rest (Aerobic) Fat and glucose are the preferred fuelsDuring Exercise1. Short duration / high intensity – Anaerobic systems used using carbohydrates.2. Long duration / low intensity – Aerobic system using carbohydrates. However, fats are used once glycogen stores are depleted.
Low intensity ATP requirements are met aerobically using the aerobic system.High Intensity Explosive movements require instant supply of ATP which can’t be met aerobically, therefore the ATP-PC and lactic acid systems need to be used anaerobically. Aerobic Anaerobic Intensity increases
Storage (Based on 80kg person) Carbohydrate rich diet; Muscle glycogen – 400g Increases glycogen stores Liver glycogen – 100g Glycogen is used in rebuildingIntake of Carbohydrates depends on ATP the intensity and duration of CHO preferred fuel over fats during exercise bouts. exercise due to requiring less Normal contribution to diet is 55- oxygen to release energy. 60% CHO Athletes need to be aware of their Carbohydrate loading (80% CHO dietary intakes of CHO. Excess intake) is used for endurance CHO is converted to fat. activities.
Storage of fats At rest Adipose tissue 50% of energy supplied by fats Triglycerides Oxygen demand is easily met to(Broken down into free fatty acids)Aerobic metabolism of fat is; burn fats Slow as it requires more oxygen Benefits of fat than CHOs. Large energy store Adds stress to the oxygen Transport medium for fat soluble transport system vitamins ATP yield is much higher from fat Negative aspects of fat (460 molecules) in comparison to Adverse health effects glucose (36). Obesity, heart disease etc.
Role of protein (Amino acids) in the body; Growth and repair Speed up reactions in the body (Enzymes) Produces hormones and antibodiesProtein and exercise1. Not used as a fuel, therefore low priority.2. Only used in extreme circumstances3. Normal diet contains enough protein (15%).Excess protein can lead to; Less intake of CHO Increase in fat intake from animal products Increase in fluid waste
During prolonged endurance events such as marathon running and triathlons; Body uses a combination of CHO and fats. Trained athletes are able to ‘spare’ glycogen and use free fatty acids. Fats cannot be used alone as a fuel (poor solubility in the blood). ‘Hitting the wall’ occurs when glycogen stores are depleted. This is called ‘hypoglycaemia’. VCE Physical Education - Unit 3
Glycemic index; Before exercise you should Rating of CHO effect on eat; blood glucose Food that maintains blood Quick breakdown with glucose levels ie.low GI food immediate effect on blood Avoid high GI food prior to glucose levels are labelled exercise. high GI High GI cause an insulin Slow breakdown are surge, effecting the labelled low GI performance of an athlete VCE Physical Education - Unit 3
Aerobic exercise includes lower intensity activities performed for longer periods of time. Activities like walking, jogging, swimming, and cycling require a great deal of oxygen to make the energy needed for prolonged exercise. The energy system that is used in aerobic exercise is called the aerobic system. It can also be called ‘oxygen system’ or the ‘aerobic glycolysis system’.
The term "anaerobic" means "without air" or "without oxygen." Anaerobic exercise uses muscles at high intensity and a high rate of work for a short period of time. Anaerobic exercise helps us increase our muscle strength and stay ready for quick bursts of speed. Examples of anaerobic exercise include heavy weight lifting, sprinting, or any rapid burst of hard exercise. These anaerobic exercises cannot last long because oxygen is not used for energy and fatiging metabolic by-products There are two energy systems which use the anaerobic pathways; ATP-PC and the Lactic Acid systems
The three energy systems do not turn on and off like a traffic light. They are always in operation – the relative contribution of each system varies depending on factors such as intensity, type of activity and duration.
How does the system work? Anaerobic PC releases a free Most rapidly available phosphate PC = P + C source of ATP ADP + P = ATP Depends on simple short chemical reactions Body has a larger storage of PC compared to ATP Stored PC last for 10 PC stores can be seconds at max replenished through aerobic recovery. intensity Once PC stores are depleted, they body must use glycogen through the anaerobic pathway.
The lactic acid system; How the system works; Activated at the start of intense Glycogen is broken down in the exercise absence of oxygen (Anaerobic More complex reactions than the glycolysis) This produces a fatigue causing ATP-PC system by product called lactic acid. Peak power until it fatigues (2-3 Lactic acid makes the muscle pH minutes) decrease (More acidic), reducing Predominant energy supplier in ATP resynthesis. events 85% max HR eg. 200m The lactic acid system; sprint. Provides twice as much energy for ATP resynthesis than the ATP- PC system. Fatiguing metabolic by-products produced at the lactate inflection point (LIP)
The exercise intensity beyond which lactateproduction exceeds removal.
The aerobic system How the system works; Slowest contributor to ATP 1. CHOs and Tryglycerides (FFA + resynthesis glycerol) broken down to release However, produces much more energy than the anaerobic systems energy. This produces pyruvic acid. Becomes major contributor once the 2. Pyruvic acid is further broken down lactic system decreases. producing carbon dioxide (Kreb’s Major contributor in prolonged cycle) exercise eg. Endurance events. 3. Further breakdown via the electron Aerobic system does contribute in transport chain. It requires hydrogen maximal intensity exercise (Eg. ions and oxygen, producing water Between 55-65% in 800m) and heat.table 4.4 p.101 and 4.5 p.102