The document discusses aerobic and anaerobic energy pathways and the three energy systems - ATP-PC, lactic acid, and aerobic. It defines aerobic and anaerobic exercise and explains that aerobic exercise relies on oxygen to produce energy through the aerobic system, while anaerobic exercise uses the ATP-PC and lactic acid systems without oxygen. The three systems work together to produce ATP but their relative contributions depend on the intensity and duration of exercise, with the ATP-PC system providing rapid energy for up to 10 seconds, the lactic acid system taking over for 2-3 minutes, and the aerobic system becoming dominant for prolonged submaximal exercise.

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

2. 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.
KeySkills
 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.

4. Food fuels and the three energy systems

5. 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

6. VCE Physical Education - Unit 3

7. VCE Physical Education - Unit 3

8. Food fuels and the three energy systems

10. Rest(Aerobic)
 Fat and glucose are the preferred fuels
During Exercise
1.
2.
Short duration / high intensity – Anaerobic systems used using carbohydrates.
Long duration / low intensity –Aerobic system using carbohydrates. However, fats
are used once glycogen stores are depleted.

12. Food fuels and the three energy systems

13. Low intensity
 ATP requirements are met aerobically using the aerobic system.
High Intensity
 Explosive movements require instant supply ofATP which can’t be met
aerobically, therefore the ATP-PC and lactic acid systems need to be used
anaerobically.
Intensity increases

14. Storage (Based on 80kg person)
 Muscle glycogen – 400g
 Liver glycogen – 100g
Intake ofCarbohydrates 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
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.

15. Storage of fats
 Adipose tissue
 Triglycerides
(Broken down into free fatty acids)
Aerobic metabolism of fat is;
 Slow as it requires more oxygen
thanCHOs.
 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.

16. 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 ofCHO
 Increase in fat intake from animal products
 Increase in fluid waste

17. During prolonged endurance events
such as marathon running and
triathlons;
 Body uses a combination ofCHO 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

18. Glycemic index;
 Rating ofCHO effect on
blood glucose
 Quick breakdown with
immediate effect on blood
glucose levels are labelled
highGI
 Slow breakdown are
labelled lowGI
Before exercise you should
eat;
 Food that maintains blood
glucose levels ie.lowGI food
 Avoid highGI food prior to
exercise.
 HighGI cause an insulin
surge, effecting the
performance of an athlete
VCE Physical Education - Unit 3

19. Food fuels and the three energy systems

20.  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’.

21.  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 LacticAcid systems

22.  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.

23. Food fuels and the three energy systems

24.  Anaerobic
 Most rapidly available
source ofATP
 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 toATP
 PC stores can be
replenished through aerobic
recovery.
 Once PC stores are
depleted, they body must
use glycogen through the
anaerobic pathway.

25. Food fuels and the three energy systems

26. 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
forATP resynthesis than theATP-
PC system.
 Fatiguing metabolic by-products
produced at the lactate inflection
point (LIP)

27. Food fuels and the three energy systems

28. The aerobic system
 Slowest contributor toATP
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)
How the system works;
1. CHOs andTryglycerides (FFA +
glycerol) broken down to release
energy.This produces pyruvic acid.
Pyruvic acid is further broken down
producing carbon dioxide (Kreb’s
cycle)
Further breakdown via the electron
transport chain. It requires hydrogen
ions and oxygen, producing water
and heat.
2.
3.

29. Foods, Fuels and EnergySystems

30. VCE Physical Education - Unit 3

31. Foods, Fuels and EnergySystems

32. 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.