-Characteristics and interplay of the 3 energy systems
(ATP-CP, anaerobic glycolysis and aerobic system)
-Fuels required for resynthesis of ATP during physical
activity and 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 type.
 We get energy from 3 food sources Carbohydrates, Fats and




Proteins (alcohol does not count)
Once consumed they are changed into chemical fuel
Glycogen. Triglyerides and Amino Acids
For our body to use any available chemical fuel it must
breakdown the molecule to help synthesis and resythesis
our energy currency ATP
Lastly we have 3 energy systems Aerobic System (with
oxygen) the Anaerobic Glycolsis System/Lactic Acid System
(no oxygen) and ATP-PC (no oxygen)
These systems can operate simultaneously, with one being
the biggest contributor towards ATP resynthesis (interplay)
ATP=ADP+P1+
energy
Anaerobic
Systems
ATP-PC
System
Anaerobic
Glycolysis
Energy
Systems
Aerobic
Systems
PC= C +P1 +
energy
Glycogen from
carbohydrates
(anearobic
Glycolysis
Glycogen from
carbohydrates (aerobic
glycolysis)
FFAs from fats
(aerobic lipolysis)
Amino Acids from
Proteins
Glucose
Energy
for
movem
ent
Glucose
Food Fuels
RDI (%)
Storage
Chemical Energy after
conversion
Carbohydrates 55-60
Ex
Glucose
Glycogen at the muscles and
liver
Proteins
Examples:
10-15
Amino Acids
As muscles at various sites
Fats
Examples
25-30
Fatty Free Acids
(FFA)
As adipose tissue at various
sites
 ATP is our energy currency! The energy released from
the breakdown (metabolism) of food is not able to be
transferred directly to cell. Therefore it is critical that
we can capture this energy in a form that can be used
for biological work. The ATP molecule offers an
effective storage solution, however ATP can only be
stored with in the body in limited amounts
(approximately 2 seconds of maximal performance).
 This is why ATP must be continually replenished or
resynthesised.
 This is achieved through the breakdown of fuel
sources by three different systems
Fats
Carbohydrates
Fatty Acids (FFA) +
Glycerol
Glucose+ Glycogen
Aerobic
oxidation
Protein
Amino Acids
Glycolysis
Aearobic
Pyruvate
Breakdown
Anearobic
Lactic
Acid
Lactate
Acetyl CoA
ATP- ADP
ATP
Resynth
esis
CO2 + H20
 Use the diagram to explain the energy release from
ATP
Adenosine
Logo demonstration
P
P
To rebuild ATP and create
more energy in a form that
muscles can use, energy from
he breakdown of
phosphocreatine (PC) or
nutrients (glucose, FFA and
AA) is used to re-join ADP and
inorganic phosphate (Pi)
P
Adenosine
P
P
+
Energy for
Movement
P
 ATP is resynthesised almost as quickly as it is broken
down
 ATP is an adenine nucleotide bound to three
phosphates
 When cells need energy, it breaks the bond between
the second and third phosphate groups, which releases
a large amount of energy
 When the cells has excess energy (from the breakdown
of PC or nutrients), it resynthesises ATP and ADP and
Pi
 Glycogen is the preferred energy source
 Glycolysis: the breakdown of glycogen either
aerobically or anaerobically.
 During Glycolysis, the glycogen is broken into
two pyruvic Acid molecules and energy is
released to form ATP.
Under aerobic conditions with
sufficient oxygen, the pyruvic
acid enters the mitochondria and
breaks down the glycogen to
produce
more ATP and CO2 and H2O
Under anerobic conditions
with insufficient oxygen,
the pyruvic acid transforms
into
lactic acid and hydrogen
ions
 We can only live for a few minutes without the constant
energy supply derived from aerobic respiration
 Cellular respiration is the set of the metabolic reactions
and processes that take place in the cells of organisms to
convert chemical energy from nutrients into adenosine
triphosphate (ATP), and then release waste products.
C6H12O6 (aq) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l)
 Aerobic respiration requires oxygen in order to generate
energies (ATP). Although carbohydrates, fats, and proteins
can all be processed and consumed as reactant, it is the
preferred method of pyruvate breakdown in glycolysis and
requires that pyruvate enter the mitochondrion in order to
be fully oxidized by the Krebs cycle.
 1. Explain the process of Carbohydrate loading?
 2. Compare and contrast the use of carbohydrates
compared to fats as a primary fuel source.
 Why are fats an important fuel source?
 Why is Protein vitally important in the diet?
 Explain the concept of Glycaemic Index? For an athlete
why is it important to understand GI foods?
ATP + Lactic Acid
Anerobic
Fats
Glucose
ATP + Co2 + H2O
Aerobic
Anerobic
Carbohy
drates
ATP + Lactic Acid
Aerobic
ATP + Co2 + H2O
What do you
notice in food
energy use
when exercise
intensities
vary?
Submaximal
Activity
Protein
Anerobic
ATP + Lactic Acid
Fats
Aerobic
Carbs
ATP + Co2 + H2O
 Energy for muscular contractions stems first from the muscle






glycogen and then the liver glycogen.
The level of carbohydrate intake varies on the nature of the activity.
Prolonged endurance activities intermittent in nature or continuous
lasting around 90minutes needs well-filled glycogen stores
While events lasting 2hours or more need ‘super-filled’ glycogen
stores obtained from carbohydrate loading.
Carbohydrate loading is the practice of increasing glycogen stores
within the muscles and the body by increasing carbohydrate intake
and tapering training time leading up to major events (up to 10
days). The diet can consist of as much as 80% carbohydrates.
This is important in order to increase glycogen stores, which
facilitate high-intensity efforts via anaerobic glycolysis as well as
aiding endurance performance (aerobic energy system)
It is important to note the crucial role that carbohydrates play in:
 The anearobic (high intensity/short duration) events, as the primary
fuel source once PC has been depleted.
 The aerobic glycolysis (moderate intensity, longer duration) as
carbohydrates require less oxygen that than the same amount of energy
converted from fats.
 Explain what role fats in our diet play?
 What form are they stored?
 Explain the oxygen cost of lipolysis.
 What is the total energy contribution of fats?
 Explain the role that protein plays in our diet?
 What function do enzymes serve?
 What is the recommended contribution of protein in
the diet? Explain why athletes may need to consume
more?
 Explain why there may be disadvantages associated
with exceeding protein intake by more than 10-15 %.
 Define glycaemic index.
 Describe and list food that are high and low in GI, offer
an explanation as to why they belong to either group.
 Identifying when it is appropriate for people to
consume either high or low GI foods.
 Explain the process of ‘fuel mixing’ during a
marathon event.
 Describe and define hyperglycaemia and what
effect does this have on an endurance athlete.
 How can an athlete develop glycogen sparing
and describe how it can be beneficial to
endurance performance?
HITTING THE WALL…
 An 80kg person can store only 100g of glycogen in the liver




and approximately 400g in the muscles (15g per kilo of
muscle). This is enough for a 25km race.
Approximately 50% of the bodies everyday energy needs is
supplied from fats
One glucose molecule yeilds 36-38 ATP in the presence of
oxygen, but only 2-3 ATP without.
Complete oxidation of a glucose molecule results in 38 ATP,
while oxidation of a triglyceride (fat) molecule yeilds 450
ATP.
However, six oxygen molecules are needed to metabolise one
6 carbon glucose molecule = 36 ATP’s per oxygen molecule.
While 26 oxygen molecules are required to produce 147 ATP’s
from one 18 carbon free fatty acid= 5.7 ATP’s per oxygen
molecule.
 Our energy systems are like a car engine. They differ in
both power/intensity and capacity/duration to sustain.
 Energy System: chemical pathways in our body that
resynthesise ATP for everyday activities.
 Power: the rate of AP resynthesis, related to intensity.
 Capacity: the yield of ATP resynthesis related to the
exercise duration
 A situation in which all three energy systems
contribute to ATP production with one system being
the major ATP producer.
Provide 2 written examples, that highlight interplay in
physical performance.
 Name the energy system in predominant use and
briefly dot point why you think this is so.
 100m in 9.58 seconds
 A 100 m sprint took Usain 9.68 seconds to complete.
 The ATP-PC Energy system was in predominant use.
- the ATP-PC energy system exhausts after around 10-15
seconds (ie PC stores are depleted after around 10-15
seconds of max activity)
- the ATP-PC system takes 3 minutes of passive rest to fully
recover PC stores
- after 30 seconds of passive rest, around 50% of PC stores
have recovered
 Production of energy throught the breakdown of PC





(phosphocreatine) to resynthesis ATP
These reactions do not require the presence of
oxygen
All activities are carried out above 100% VO2max
(the maximum amount of oxygen that can be taken
up, transported and utilised per minute).
Stored ATP= 2seconds of exercise, therefore
regeneration is needed.
Copy fig 5.6 Page 125
PC is stored in the muscles and contains phosphate
bonds which when broken apart provide energy that
results in linked resynthesis of ATP.
 ADP+Pi is reformed using the energy released
from the breakdown of PC.
 ATP-PC system is exhausted quickly, after 6-10
seconds of intense muscular activity.
 PC is replenished within 3 minutes of the
activity ceasing and a passive recovery time.
 Once PC is depleted at the muscle, ATP must
be resynthesised from another substancetypically this is glycogen via anaerobic
glycolysis.
 http://www.youtube.com/watch?v=9GaDqzSDBk8
 At competition level rowing a race of 2000m takes
between 5.5 and 8.0 minutes requiring maintenance of
high power for the duration
 Rowing places great demands on both the aerobic and
anaerobic energy systems and requires great power
and strength.
 Aerobic energy is thought to account for 70-75% of the
energy and anaerobic energy for the remaining 20 25%.
 Energy provided through the incomplete breakdown of glucose when oxygen is







not available
Glycogen stores in the muscles can only sustain maximum effort for about 20
seconds.
All pyruvic acid produced is converted into lactic acid, which lead to the byproduction of Hydrogen ions (H+)
These ions are responsible for impeding maximal muscle contractions, due to
the inhibition of certain enzymes.
Reduced muscle contractility is a safety mechanism employed to stop the
destruction of cells in acidic conditions.
The hydrogen ions then combine with pyruvate to form lactate, which is then
converted to glycogen and made available to release further energy.
Around 80% of lactic acid is diffused from the muscles and circulated through
the liver for reconversion into glucose, although some H+ ions accumulate in
muscle tissue, making muscle contraction painful and cause fatigue.
Copy figure 5.7
 The exercise intensity beyond which lactate production exceeds removal in the



1.
2.

blood.
This can be referred to as anaerobic threshold, lactate threshold, onset of blood
lactate accumulation (OBLA), maximal lactate steady state or LIP
The LIP reflects the last point where lactate entry into and removal from the
blood are balanced. It is identified as the final exercise intensity or oxygen
uptake value at which blood lactate concentration is relatively stable during
maximal aerobic exercise. A maximal intensity at which blood lactate is stable.
Lactate removal in the cells cytoplasm occurs via different mechanisms:
Lactate to be reconverted to pyruvate for immediate oxidation in
mitochondria
Lactate to be transported out to the blood, which is then oxidised by other
muscles (heart, slow twitch fibres) and some is converted into glucose in the
liver.
Lactate production in cells increases in direct proportion to increased workrate. However, lactate concentrations remain relatively stable during submaximal rates, as the body is able to remove it at a similar rate to its appearance
in the blood.
Can you identify LIP on the graph?
Describe what you see in the data. Offer an explanation
for this.
Describe how lactate accumulates beyond LIP?
 Imagine a person in a boat that has sustained a leak. Whilst the leak
flows slowly the person can easily use a bucket to scoop the incoming
water out of the boat. As the hole gets bigger and the water flows
more rapidly the person will still be able to empty the water at a rate
faster than it is coming in and things are OK. BUT, as soon as the
water comes in at a faster rate than it can be removed the person is in
trouble because the water will increasingly accumulate in the boat
until it eventually sinks. The point at which the entry of water
exceeds the rate at which it can be removed is where LIP has been
exceeded. Think about the associated workloads and students
quickly picture the rate of entry vs. bucketing and at maximal levels a
steady state is reached but this cannot be sustained for long before
the water starts to rise and fill the boat – this also allows us to discuss
lactate shuttling (moving the water from the boat to it’s
surroundings)
 Wheelie Bin activity with bean bags
http://www.youtube.com/watch?v=CmhrPdkW1cE&feat
ure=related
 The complete breakdown of glucose when plenty of oxygen is






available.
Produces energy through glycolysis (glycogen-preferentially
during exercise) and lipolysis (free fatty acids-during rest)
Aerobic energy production takes the most amount of chemical
reactions, with APT production at the slowest rate but with the
greatest yield and supply for the longest duration.
Steady state is when sufficient oxygen is supplied to meet
demand.
Using the aerobic system, any lactate production has the
capability to be oxidised/removed or converted back into
glycogen.
Again, there is a higher O2 cost when breaking down fats, which
is why performers are forced to slow down when fats are used
during high-intensity activities or of extended durations
Study and copy table 5.4 and figure 5.9 on page 129
Intensity
Total Event
Duration
Rest
n/s
Submaximal
30 seconds
Submaximal
30 minutes
Submaximal
3+ hours
Maximal
1-3 seconds
Maximal
5 seconds
Maximal
30 seconds
Maximal
75 seconds
Dominant
Energy System
Fill in the remaining two columns.
Food/Chemical
Fuel
.
2. .
3. .
4. .
1.
 Review Figure 5.11 (p. 137). Explain how the three
systems overlap and vary their contribution to
energy/ATP production depending on the duration of
the activity.
 Review Figure 5.12. What is oxygen deficit? Explain
how the contributions from the aerobic and anaerobic
system as the length of an event increases.
 Review Table 5.8. which highlights the total possible energy
(yield) and the ‘running time’ or rate of depletion for
various fuels when working at 75% of max HR.
 Review Table 5.9. Draw in books. This confirms that when
the aerobic system is activated and becomes the major
energy contributor, it provides 50 times more energy
(moles of ATP) than the ATP-PC and Lactic acid system
combined.
 In early stages of exercise (low oxygen and transport) the
two anaerobic systems supply APT
 Notice the trade off between rate and yield for each of the
energy systems. As the rate of ATP resynthesis increases,
the yield (amount of ATP being produced) decreases.
 What is specificity and how does it apply to improving
performance?
 Outline 2 ways to improve the :
1. ATP-PC system
2. The lactic Acid System
3. The aerobic system
Copy Table 5.11 (p.141) into books and interpret.
Characteristics
Fuel Source
Intensity of
Activity
Duration system
is dominant
during activity
peak power
Amount of ATP
produced
Speed of
production of
ATP
By product
ATP-PC System
Lactic Acid
System
Aerobic Energy
System
 Study table 5.2. Copy into books and discuss
 When we take a hot shower the exhaust fan can handle the
build up of steam and as long as the fan sucks out the
steam faster than it is being built up things are OK – the
mirror doesn’t fog up. But, if we crank up the hot water the
steam will occur more rapidly and in greater volumes –the
exhaust fan might still be able to handle this and as long as
the mirror doesn’t fog up we haven’t triggered the “MFP”
(mirror fogging point). This goes on until a maximal steady
steam state (MSSS) is achieved and the largest amount of
steam can barely be removed by the fan. Any more steam
beyond this point will cause the mirror to steam up
because rate of steam production exceeds rate of steam
removal (by the fan).
