Introduction to the energy systems

Aerobic and anaerobic pathways – an introduction to the energy systems

Aerobic and anaerobic pathways – an introduction to the energy systems

Text Reference

1. Nelson Physical Education VCE Units 1&2 – Chapter 3

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What do I need to know?

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 FuelsFood fuels and the three energy systems

Food Fuels for Energy

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

Foods High in CHO, Fats and Proteins

VCE Physical Education - Unit 3

Adenosine Triphosphate (ATP)

Food fuels and the three energy systems

Food Fuels at Rest

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.

Maximal and Sub-maximal Activity

Contributions of Carbohydrates, Fats and Protein to Energy Production

Food fuels and the three energy systems

Energy Demands - Intensity

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

Carbohydrate Contributions

Storage (Based on 80kg person)

Muscle glycogen – 400g Liver glycogen – 100gIntake of Carbohydrates

depends on the intensity and duration of exercise bouts.

Normal contribution to diet is 55-60% CHO

Carbohydrate loading (80% CHO intake) is used for endurance activities.

Carbohydrate rich diet; Increases glycogen stores Glycogen is used in

rebuilding ATPCHO 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.

Fat Contributions

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 fatsBenefits of fat Large energy store Transport medium for fat

soluble vitaminsNegative aspects of fat Adverse health effects Obesity, heart disease etc.

Protein Contributions

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

VCE Physical Education - Unit 3

Prolonged Endurance Events

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 (GI)

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

The Three Energy SystemsFood fuels and the three energy systems

Aerobic Exercise

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’.

Anaerobic Exercise

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

Common Mistake

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

The ATP-PC SystemFood 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

The ATP-PC System

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.

The Lactic Acid SystemFood fuels and the three energy systems

The Lactic Acid System

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)

The Aerobic SystemFood fuels and the three energy systems

The Aerobic System

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.

Comparing the Three Energy SystemsFoods, Fuels and Energy Systems

VCE Physical Education - Unit 3

Energy System InterplayFoods, Fuels and Energy Systems

Interplay Between 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.

Anaerobic v Aerobic Contributions