Aerobic and anaerobic pathways – an introduction to the energy systems Text Reference 1.Nelson Physical Education VCE Units 1&2 – Chapter 3.

Key Knowledge  Introduction to the characteristics of aerobic and anaerobic pathways (with or without oxygen) and their contribution to movement and dominant fibre type associated with each pathway. Key Skills  Identify the dominant energy pathway utilised in a variety of aerobic or anaerobic activities determined by the intensity and duration of the activity. Collect, analyse and report on primary data related to responses to exercise and anaerobic and aerobic pathways.

Food fuels and the three energy systems

1. Carbohydrates (CHO) – Preferred source of fuel during exercise (Glycogen) 2. Fat – Concentrated fuel used during rest and prolonged sub-maximal exercise. 3. Protein – Used for growth and repair (Negligible use during exercise) Energy

VCE Physical Education - Unit 3

Food fuels and the three energy systems

Rest (Aerobic)  Fat and glucose are the preferred fuels During Exercise 1. 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.

Food fuels and the three energy systems

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. AerobicAnaerobic Intensity increases

Storage (Based on 80kg person)  Muscle glycogen – 400g  Liver glycogen – 100g Intake of Carbohydrates depends on the intensity and duration of exercise bouts.  Normal contribution to diet is % CHO  Carbohydrate loading (80% CHO intake) is used for endurance activities. Carbohydrate rich diet;  Increases glycogen stores  Glycogen is used in rebuilding ATP CHO preferred fuel over fats during exercise due to requiring less oxygen to release energy. Athletes need to be aware of their dietary intakes of CHO. Excess CHO is converted to fat.

Storage of fats  Adipose tissue  Triglycerides (Broken down into free fatty acids) Aerobic metabolism of fat is;  Slow as it requires more oxygen than CHOs.  Adds stress to the oxygen transport system  ATP yield is much higher from fat (460 molecules) in comparison to glucose (36). At rest  50% of energy supplied by fats  Oxygen demand is easily met to burn fats Benefits of fat  Large energy store  Transport medium for fat soluble vitamins Negative aspects of fat  Adverse health effects  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 antibodies Protein and exercise 1. Not used as a fuel, therefore low priority. 2. Only used in extreme circumstances 3. 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;  Rating of CHO effect on blood glucose  Quick breakdown with immediate effect on blood glucose levels are labelled high GI  Slow breakdown are labelled low GI Before exercise you should eat;  Food that maintains blood glucose levels ie.low GI food  Avoid high GI food prior to exercise.  High GI cause an insulin surge, effecting the performance of an athlete VCE Physical Education - Unit 3

Food fuels and the three energy systems

 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. X

Food fuels and the three energy systems

 Anaerobic  Most rapidly available source of ATP  Depends on simple short chemical reactions  Stored PC last for 10 seconds at max intensity How does the system work?  PC releases a free phosphate PC = P + C ADP + P = ATP  Body has a larger storage of PC compared to ATP  PC stores can be replenished through aerobic recovery.  Once PC stores are depleted, they body must use glycogen through the anaerobic pathway.

Food fuels and the three energy systems

The lactic acid system;  Activated at the start of intense exercise  More complex reactions than the ATP-PC system  Peak power until it fatigues (2-3 minutes)  Predominant energy supplier in events 85% max HR eg. 200m sprint. How the system works;  Glycogen is broken down in the absence of oxygen (Anaerobic glycolysis)  This produces a fatigue causing by product called lactic acid.  Lactic acid makes the muscle pH decrease (More acidic), reducing ATP resynthesis. The lactic acid system;  Provides twice as much energy for ATP resynthesis than the ATP- PC system.  Fatiguing metabolic by-products produced at the lactate inflection point (LIP)

Food fuels and the three energy systems

The aerobic system  Slowest contributor to ATP resynthesis  However, produces much more energy than the anaerobic systems  Becomes major contributor once the lactic system decreases.  Major contributor in prolonged exercise eg. Endurance events.  Aerobic system does contribute in maximal intensity exercise (Eg. Between 55-65% in 800m) table 4.4 p.101 and 4.5 p.102 How the system works; 1. CHOs and Tryglycerides (FFA + glycerol) broken down to release energy. This produces pyruvic acid. 2. Pyruvic acid is further broken down producing carbon dioxide (Kreb’s cycle) 3. Further breakdown via the electron transport chain. It requires hydrogen ions and oxygen, producing water and heat.

Foods, Fuels and Energy Systems

VCE Physical Education - Unit 3

Foods, Fuels and Energy Systems

All activities use some energy from all three systems. The energy systems overlap – they never work independently. It it’s the relative contribution of each system that varies.