Introductory Slides for energy systems. Delivered to year 10 including class activity. Credit: http://www.slideshare.net/kerrieobryan/introduction-to-the-energy-systems

1. SPORT SCIENCE
AN INTRODUCTION TO THE ENERGY SYSTEMS

2. WHAT DO I NEED TO KNOW?

4. FOOD FUELS
FOOD FUELS AND THE THREE ENERGY SYSTEMS

5. 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

6. VCE Physical Education - Unit 3

7. ADENOSINE TRIPHOSPHATE
(ATP)
FOOD FUELS AND THE THREE ENERGY SYSTEMS

9. FOOD FUELS AT REST
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.

10. MAXIMAL AND SUB-MAXIMAL ACTIVITY

11. CONTRIBUTIONS OF CARBOHYDRATES, FATS
AND PROTEIN TO ENERGY PRODUCTION
FOOD FUELS AND THE THREE ENERGY SYSTEMS

12. 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.
Anaerobic

13. VCE Physical Education - Unit 3
Intensity increases

14. CARBOHYDRATE CONTRIBUTIONS
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 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. 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 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. PROTEIN CONTRIBUTIONS
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

17. 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

18. THE THREE ENERGY SYSTEMS
FOOD FUELS AND THE THREE ENERGY SYSTEMS

19. 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’.

20. 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

21. THE ATP-PC SYSTEM
FOOD FUELS AND THE THREE ENERGY SYSTEMS

22. THE ATP-PC SYSTEM
▪ 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.

23. THE LACTIC ACID SYSTEM
FOOD FUELS AND THE THREE ENERGY SYSTEMS

24. 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)

25. THE AEROBIC SYSTEM
FOOD FUELS AND THE THREE ENERGY SYSTEMS

26. 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.

27. 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.

28. ENERGY SYSTEM INTERPLAY
FOODS, FUELS AND ENERGY SYSTEMS

29. ACTIVITY
▪ Students running the red line walk a
slow pace (up and back) to
demonstrate the aerobic system
▪ Students on orange line walk fast
(up and back) to demonstrate lactic
acid system
▪ Students on green line run (up and
back) to demonstrate ATP-PC system
▪ Film using camera and replay to
students after completion.
VCE Physical Education - Unit 3

30. 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.