SIR THOMAS RICHS

1
SIR THOMAS RICHS
SCHOOL
A2 PHYSICAL EDUCATION
Energy Systems
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The currency of Energy Adenosine
Triphosphate ATP
Adenosine
P
P
P
Energy is stored in the bonds that join this
compound (High energy bonds). If the bonds are
broken or split energy is released.
ATP is stored within the muscle cells (at the end
of cross bridges).
The limited supply can fuel up to 2 seconds of
Intense activity.
ATP ADP P
ENERGY
In order to sustain movement for long periods,
the body has adopted three energy systems to
replenish the supply of ATP.
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Phosphocreatine system
The first fuel reserve to be called upon when ATP
is being used is Phosphocreatine (PC) Which is
stored in muscle fibres. The muscle store
concentration of PC is 3 to 5 greater than that
of ATP.
P
Creatine
ENERGY
Step 1 PC Creatine
Pi Energy
Step 2 Energy ADP Pi
Energy
Without this system fast intense movements would
not be possible. (2 10 secs).
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Task One In groups, think of as many reasons as
you can for the Phosphocreatine system being the
most rapid source of ATP.

• It does not require oxygen.
• Both ATP and PC are stored directly within the
  contractial mechanism of the muscle.
• Dependant on simple chemical reactions.

Energy released 1 mole of PC resynthesis
1 mole of ATP.
Task Two In pairs, state what training methods
you would use to train this system, whether the
training would be of high or low intensity and
how much rest would you use.
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HIGH INTENSITY EXERCISE

• SHORT-TERM RESPONSES
• ATP muscle stores are depleted within 2 seconds
• ATP/PC system
• rising ADP levels stimulate the breakdown of PC
  stores
• in coupled reaction with ADP pool
• peak anaerobic power attained within first 5
  seconds of flat-out exercise
• depletion of PC occurs between 7-9 seconds

• on the graph, the ATP level is maintained (after
  an initial small drop) then falls as PC is used
  up by the energy from PC being used to
  resynthesise ATP.
• so PC levels fall rapidly.
• capacity to maintain ATP production at this point
  depends on lactic acid system

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Training the Phosphocreatine system

• EFFECTS OF TRAINING ON THE ALACTIC ANAEROBIC
  SYSTEM
• muscle cells adapt by
• increase in ATP and PC stores
• therefore the ATP / PC system provides energy for
  slightly longer when exercise is taken at maximum
  effort
• the alactic / lactic threshold is delayed

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Phosphocreatine system

• for activity which lasts between 3 and 10 seconds
• for high intensity maximum work
• example flat out sprinting - 100m sprint
• no oxygen is needed - ANAEROBIC
• the chemical reactions within this system are a
  coupled reaction

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LONG-TERM ADAPTATIONS TO HIGH INTENSITY TRAINING

• LONG-TERM ADAPTATIONS TO AN ANAEROBIC TRAINING
  PROGRAMME
• increases in stores of ATP and PC
• and amounts of anaerobic enzymes such as creatine
  kinase
• result in more energy to be available more
  rapidly
• and therefore increases in maximum possible peak
  power
• and a delay in the ATP/PC to lactic threshold

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Exam Questions

• State why the phosphocreatine system is an
  effective source of energy for some sportspeople.
• Also outline its limitations.

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Lactic Anaerobic Pathway
This system depends on a chemical process known
as GLYCOLYSIS. C6 H12O6 carbohydrates
In the body all carbohydrates are converted to
simple sugar glucose. This can be used
immediately in this form, or stored in the
muscles/liver as glycogen.
Similar to the phosphagen stores the muscle
glycogen stores are high in energy and it takes
place in the sarcoplasm of the muscle cell.
Glycolysis simply means the splitting of glucose.
However as the lactic acid system functions
without oxygen, anaerobic glycolysis refers to
the partial breakdown of glucose in the absence
of oxygen.
Chemically this process is more complicated than
the phosphocreatine system, as it relies on 12
separate but sequential chemical reactions.
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How it works
Anaerobic glycolysis is therefore another fast
source of energy. High intensity events of 30
secs to 3 minutes rely heavily on this lactic
acid system, for example
800m
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Summary Anaerobic glycolysis/ Lactic Acid system

• Results in the formation of lactic acid, hence
  fatigue.

• Does not require oxygen.

• Uses carbohydrates (CHO) as fuel, more
  specifically (muscle glycogen)

• Energy released equals 2 moles of ATP.

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How lactic acid works

• 400m race
• Glycogen is broken down anaerobically and lactic
  acid is produced.

• If the lactic acid accumulates it lowers the
  pH, which affects the bodys ability to
  resynthesize ATP temporarily, causing fatigue.

• The accumulation of lactic acid also
  interferes with cross- bridge formation within
  the muscle cell, again contributing to a decrease
  in performance.

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• EFFECTS OF CONTINUED HIGH INTENSITY EXERCISE
• as work intensity increases lactic acid starts to
  accumulate above resting values
• this produces muscle fatigue and pain
• the resultant low pH inhibits enzyme action and
  cross bridge formation
• hence muscle action is inhibited
• physical performance deteriorates

EVENTS AND SPORTS up to 30 - 60 seconds. 400m
run 100m swim After exercise stops, extra oxygen
is taken up to remove lactic acid by changing it
back into pyruvic acid, the OXYGEN DEBT
OBLA Onset of blood lactate accumulation is the
point at which blood lactate becomes extensive
enough to suppress performance OBLA depends on
the level of training and lies between 2 and 4
mmol l-1
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Anaerobic Threshold

• This relates to intensity of continuous exercise
  at which a subject can no longer resynthesize
  sufficient energy via the aerobic system.

• Onset of Blood Lactate Accumulation (OBLA) is
  gradual and starts at relatively low levels.

LONG-TERM ADAPTATIONS OF OBLA TO AEROBIC
TRAINING This point governs the lactic aerobic
threshold. Trained athletes begin OBLA at higher
work intensities and can tolerate higher levels
of blood lactate during moderate exercise and
higher values of VO2max than untrained people
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• Exam Question
• Explain how lactate (lactic acid) is removed from
  the blood by the body. (4 marks)

• Mark Scheme answers
• Converted to pyruvate / pyruvic acid.
• Then to CO2 water
• In active muscles and tissues.
• Converted to glycogen/glucose
• In liver
• Some excreted in sweat/urine/conversion to
  protein.

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Production of ATP using the AEROBIC system

• The key factor in producing large amounts of ATP
  from glycogen and fat is the presence of oxygen.

• 1 mole of glycogen is broken down to CO2 AND
  H2O (in the presence of oxygen) releasing enough
  energy to resynthesize 36 moles of ATP.

• Like the Anaerobic systems, the reactions of the
  Aerobic system occur within the muscles but
  unlike the anaerobic systems they are confined to
  specialised compartments called Mitochondria.
  Mitochondria are deemed the powerhouses of the
  cells because they are the sights for ATP
  production.

• Mitochondria can self replicate (they can
  divide to form new ones). During an intensive
  aerobic training programme there is an increase
  in the number, size and membrane surface area of
  skeletal muscle mitochondria.

• Following a 20 week, five day a week training
  programme of running, a study reported an
  increase of 120 in the number of mitochondria,
  an increase of up to 40 in the size of
  mitochondria.

• The aerobic system relies on oxygen being
  present to completely breakdown CHOs and fats to
  CO2 and water and energy for ATP resynthesis.

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• The reactions of the aerobic system can be
  divided into 3 main series
• Glycolysis
• Kreb Cycle
• Electron Transport System

STAGE ONE - GLYCOLYSIS this takes place in muscle
cell SARCOPLASM and is identical to the lactic
acid system ATP regenerated 2ATP per molecule
of glucose
STAGE TWO - KREBS CYCLE occurs in the presence
of oxygen, taking place in the muscle cell
MITOCHONDRIA. Pyruvic acid (from glycolysis) or
fatty acids (from body fat) facilitated by the
or protein (keto acids - from muscle) act as the
fuel for this stage.
STAGE THREE - ELECTRON TRANSPORT CHAIN occurs in
the presence of oxygen within the cristae of the
muscle cell MITOCHONDRIA hydrogen ions and
electrons have potential energy which is released
to produce the ATP.
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THE AEROBIC SYSTEM
STAGE ONE - GLYCOLYSIS
STAGE TWO - KREBS CYCLE 2 molecules of pyruvic
acid combine with oxaloacetic acid (4 carbons)
and acetyl coA (2 carbons) to form citric acid (6
carbons) the cycle produces H and electron
pairs, and CO2, and 2 ATP
STAGE THREE - THE ELCTRON TRANSPORT CHAIN the H
and electron pairs have potential energy which is
released in a controlled step by step
manner oxygen combines with final H ions to
produce water and 32 ATP
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The Kreb Cycle

• The pyruvic acid formed during aerobic glycolysis
  continues to be broken in a series of reactions
  called the Kreb Cycle.
• Three important things happen during the cycle
• Carbon dioxide is formed.
• Oxidation takes place hydrogen is removed from
  the compound.
• Sufficient energy is released to synthesise 2
  molecules of ATP.

The removal of electrons and the production of
carbon dioxide in the Kreb Cycle is related.
Pyruvic acid (2C3H4O3) in its modified form
contains carbon, hydrogen and oxygen. When
hydrogen is removed, carbon oxygen remain (CO2).
The hydrogen atoms are then diverted into the
ETS.
The Electron Transport System
Coenzymes NAD FAD carry the hydrogen atoms
through the ETS. For each pair of hydrogen atoms
that enter this pathway, the net effect is the
production of 2 molecules of ATP and 1 molecule
of water. At the end of the chain the final pair
is accepted by the molecule of oxygen which
combines with H to form water.
The energy yield from the ETS is 34 molecules of
ATP. This means that the total yield of aerobic
respiration (from the three stages combined) is
38 molecules of ATP. Therefore the aerobic system
is the most efficient in terms of the energy
produced and the by products (carbon dioxide and
water) are easily expelled from the body.
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• Summary of the Aerobic System
• It is efficient
• However the reactions involved in this system
  depend on the availability of oxygen and at the
  onset of exercise and during very intense
  exercise, the oxygen distributed to the cells
  just isnt enough for the body to rely on this
  system as a way of replenishing ATP stores.
• At sub-maximal exercise the aerobic system is the
  predominant method of ATP production as oxygen
  can be delivered at a rate to match the oxygen
  demand and unless you run out of carbs, fats and
  protein stores, the system is unlimited.

Glucose (C6H1206) Oxygen (6O2) Carbon Dioxide
(6CO2) Water (6H2O) Energy
Energy 38 ADP 38 P 38 ATP
Stage 1 (Aerobic glycolsis) 2 ATP Stage 2
(Kreb Cycle) 2 ATP Stage 3 (ETS)
34 ATP Total yield 38 ATP
So far we have looked at how glycogen stores are
broken down aerobically to produce ATP, but both
fats and proteins may also be used as a fuel for
ATP synthesis.
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SHORT-TERM RESPONSE TO AEROBIC ACTIVITY

• THE AEROBIC SYSTEM
• requires CHO in the form of glucose
• which is derived from glycogen stored in muscle
  cells (mostly ST slow twitch)
• or in the liver
• the graph shows how the rate of usage of muscle
  glycogen is high during the first 30 minutes of
  steady exercise

• the amount of glycogen remaining
  depends on the intensity and duration of the
  exercise
• and the CHO content of diet prior to exercise.
• once the glycogen is used it may take days
  to fully replenish
• again depending on diet.

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Energy from fats

• Fat is stored as Triglycerides.
• The breakdown is controlled by enzymes called
  lipases.
• Triglycerides enter the Kreb cycle similar to the
  products of glycogen breakdown.
• Triglycerides contain lots of high energy
  carbon-hydrogen bonds which when broken release
  a lot of energy.
• The amount of energy released from fat is much
  more than from carbs, however the breakdown of
  triglycerides requires about 15 more oxygen.
• So when the supply is limited, glycogen stores
  will be broken down instead of triglyceride
  stores.
• Another problem is that the presence of lactic
  acid inhibits the breakdown of fat, and increase
  in insulin has a similar effect
• If you want to burn fat what do you need to do?
• Implications for marathon runners?

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Energy from Proteins

• It is possible to use protein as an energy source
  for ATP synthesis, however we rarely do. Protein
  is oxidised only when the body is in a state of
  starvation.

• Two-carbon compound from the breakdown of
  proteins also enter the Kreb Cycle.

• Task
• What would be the predominant energy system used
  to resynthesize ATP in the following activities.
• Resting
• 30 m sprint
• 4 mile steady run
• Gymnastic tumbling routine
• A full court man-to-man defence in basketball
  followed by a fast break.

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THE ENERGY CONTINUUM

• THE ENERGY CONTINUUM
• this describes the process by which ATP is
  regenerated via the different energy systems
• depending on the intensity and duration of
  exercise
• each of the alactic, lactic acid and aerobic
  systems contribute some ATP during the
  performance of all sports
• one or other of the energy systems usually
  provides the major contribution for a given
  activity
• the diagram shows approximate proportions of ATP
  resynthesised via aerobic / anaerobic for some
  sporting activities

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THE ENERGY CONTINUUM

• OTHER FACTORS AFFECTING THE PROPORTIONS OF ENERGY
  SYSTEMS
• used in any given exercise activity are
• level of fitness (whether adaptations to training
  have included enhancement of relevant enzymes -
  which would for example postpone levels of
  lactate accumulation)
• availability of O2 and food fuels, for example a
  high CHO diet would assist replenishment of
  glycogen stores which would then be available for
  glycolysis

VARIATION IN CONTRIBUTION OF ENERGY SYSTEMS as
time progresses during intense exercise, the
following chart shows the contribution of the
different energy systems to the resynthesis of
ATP
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Oxygen Debt EXCESS POST-EXERCISE OXYGEN
CONSUMPTION (EPOC)
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Oxygen Deficit

• When we start to exercise insufficient oxygen is
  being distributed to the tissues for all the
  energy production to be met aerobically.
• It takes time for the circulatory system to
  respond to the increase in demand for oxygen and
  the rate of aerobic respiration in the
  mitochondria also takes time to adjust.
• Meanwhile the two anaerobic systems have to be
  used to satisfy the increased demand for ATP.
  This has traditionally known as the Oxygen Deficit

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• Phosphocreatine stores have to be broken down
  and the energy released is used to resynthesize
  ATP.
• Once these stores have been broken down they
  cannot be built up again until sufficient energy
  is available.
• Glycogen stores are also broken down
  anaerobically, producing lactic acid.
• The lactic acid must be removed during the
  recovery process so the blood pH returns to
  normal.
• It is important to note that you dont have to
  actually stop exercising to give your body an
  opportunity to recover, but the intensity of the
  exercise has to be significantly reduced.

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THE RECOVERY PROCESS

• EXCESS POST-EXERCISE OXYGEN CONSUMPTION (EPOC)
• this is the excess O2 consumed following exercise
• needed to provide the energy needed to
  resynthesise ATP used
• and remove lactic acid created during previous
  exercise
• EPOC has two components
• ALACTIC
• LACTIC

AIM OF RECOVERY PROCESS to replace ATP and
glycogen stores as soon as possible. OXYGEN
DEFICIT the difference between the O2 required
during exercise and the O2 actually consumed
during the activity
OXYGEN DEBT the graph shows the relationship
between O2 consumption and the time before,
during and after exercise
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THE ALACTACID COMPONENT involves the conversion
of ADP back into PC and ATP this is known as
restoration of muscle phosphagen and is a very
rapid process (120 seconds to full
restoration) size 2 to 3.5 litres of O2
this is achieved via THREE MECHANISMS aerobic
conversion of carbohydrates into CO2 and H2O to
resynthesise ATP from ADP and Pi some of the ATP
is immediately utilised to create PC using the
coupled reaction ATP C ---gt
ADP PC small amount of ATP is resynthesised
via glycogen producing small amounts of lactic
acid
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THE RECOVERY PROCESS

• IMPLICATIONS FOR INTERVAL TRAINING
• if there is only a short interval between bouts
  of exercise
• level of phosphagen stores gradually reduces

EFFECTS OF TRAINING ON THE ALACTACID
COMPONENT increase ATP and PC stores in muscle
cells improved ability to provide O2 As muscle
phosphagen stores provide the energy for short
intensive bouts of exercise, the stores can be
replenished very quickly. In a game that relies
heavily on anaerobic energy systems, such as
basketball, the coach may schedule timeouts to
help his team recover. The time may not be
sufficient to gain full recovery but at least
some stores will be available for energy
production. As phosphocreatine stores become
available this will reduce the contribution made
by the lactic acid system and will therefore
reduce the amount of lactic acid being produced.
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LACTACID OXYGEN RECOVERY high intensity exercise
up to 60 seconds creates lactic acid oxygen is
needed to remove this lactic acid the process
begins to restore muscle and liver glycogen
RECOVERY the process is relatively slow full
recovery takes up to 1 hour relatively large
amounts of lactic acid are produced during high
intensity exercise.
FATE OF THE LACTIC ACID Most (over 60 ) of the
lactic acid is removed from the cells by
converting it into pyruvic acid. The pyruvic acid
enters the Kreb Cycle and is metabolised
aerobically into carbon dioxide, water and
energy. The energy needed to convert the lactic
acid back to pyruvic acid is made available
aerobically because of the elevated rate of
respiration during recovery. This is one of the
reasons why an active recovery is recommended.
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EFFECT OF COOL-DOWN ON LACTIC ACID REMOVAL

• REMOVAL OF LACTIC ACID FOLLOWING EXERCISE
• cool-down continues to provide oxygen to skeletal
  muscle
• which therefore enhances oxidation of lactic acid
• and ensures that less lactic acid remains in
  tissue
• and there is less muscle soreness

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• Other fates of lactic acid are conversion to
  protein or to glycogen in muscle and liver, or
  excretion via urine and sweat.
• Recent studies have suggested EPOC isnt
  entirely dedicated to the removal of lactic acid
  and the resynthesis of phosphagen stores and that
  other processes also require an elevated rate of
  oxygen consumption.
• Other processes are 1. Elevated breathing and
  heart rates. CO2 is a waste product that needs to
  be expelled from the body and this is achieved
  through increased circulation and respiration. 2.
  Body Temperature. This remains relatively high
  and therefore keeps respiratory and metabollic
  rates higher than normal.
• Elevated hormonal levels have a similar effect
  to an increase in body temperature, but when the
  body stops exercising the levels of noradrenaline
  and adrenaline quickly drop and therefore may not
  have a particularly significant role in the terms
  of EPOC.

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Aerobic Capacity
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Aerobic Capacity

• The maximum amount of oxygen that can be taken
  in and used by the body in one minute. This is
  known as a persons VO2 max and is expressed in
  millilitres per kilogram of body weight.

• Mean value at rest 0.2 to 0.3 l min-1
• During maximal exercise a persons VO2 max can
  increase to 3-6 litres. This is the maximum
  amount of oxygen a person can utilise.
• mean values are
• males (20 yo) 3.5 l min-1
• 40 ml kg-1 min-1
• (for average male body mass 87.5 kg)
• females (20 yo) 2.3 l min-1
• 35 ml kg-1 min-1
• (for mean female body mass 66 kg)
• endurance athlete 4 to 6 l min-1
• 75 ml kg-1 min-1
• (for mean body mass 66 kg)

When a given amount of oxygen breaks down a given
amount of fuel a specific amount of energy is
released. However it is too difficult to monitor
the amount of energy released but it is possible
to monitor how much oxygen is consumed. This is
done by collecting the expired air of an athlete
and comparing how much oxygen is in the expired
air with that of atmospheric air. (Sport PE,
Wesson et al. p. 142)
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Relationship between VO2 max and OBLA/Lactate
Threshold
A persons VO2 max depends on the efficiency of
their cardiac, respiratory and vascular systems
along with their physiological make up in terms
of muscle fibre type.
A person may improve their VO2max by 20 but they
still may be more suited to anaerobic activities.
When sufficient oxygen cant be delivered to the
muscles, the anaerobic systems are used. This
usually occurs when the activity is very intense.
The most reliable way of monitoring the
contribution of the lactic acid system to energy
production is to measure the amount of lactic
acid in the blood.
A small amount of lactic acid in the blood is
always present but when the level starts to
increase rapidly the body is relying heavily on
the lactic acid system for energy production.
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Many elite swimmers use blood lactate sampling
during training as a means of establishing their
training load.
1. (i) What do you understand by the term lactate
threshold? (2)
Levels at which lactate Lactic Acid accumulates
in the blood Exercise has become anaerobic. Any
2 for 2 marks.
(ii) How is lactate threshold related to VO2
max? (2)
Lactate threshold is some proportion/percentage
of VO2 max Proportion/percentage increases as
fitness increases. 2 marks.
(iii) Explain how knowing blood lactate
levels during a swim might help assist an elite
performer
(2)
Accurately measures intensity of training Elite
performers need to train close to their Lactate
threshold/VO2 max Accuracy in determining
Lactate Threshold/ VO2 max is difficult. Any 2
for 2 marks.
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AEROBIC CAPACITY
FACTORS AFFECTING VO2max Age it decreases with
age. Gender women have less muscle, smaller
hearts and therefore lower cardiac
output Availability of O2 in the tissue whether
haemoglobin arriving at tissue is fully saturated
with O2. The limitations of the cardiovascular
and pulmonary systems which varies from
individual to individual. Whether myglobin in
muscle cells is fully saturated with O2 (has
sufficient recovery time elapsed?) Reduction in
VO2max will cause decline in aerobic performance.
Exam Question
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More Exam Questions 1. What do you understand by
the term VO2 max? (2)
Maximal amount of oxygen consumed/taken
up/used Per minute/time. 2 Marks
2. Suggest reasons why VO2 max is regarded as
such an important measure of a performers
ability. (2)
Oxygen consumption is linked to (aerobic) energy
use Suggestion that relevance is for
endurance/stamina/aerobic performance (Do not
credit lasting the game).
3. Describe and explain how lactate threshold
varies as fitness improves. (3)
Lactate Threshold is delayed LT is when lactate
accumulates in blood OBLA When fitter- LT occurs
at higher of VO2 max/workload. Elite performers
can tolerate slightly higher levels of
lactate Because they can remove it more
quickly Lactate can be converted to
protein/glycogen/CO2 and water/pyruvic acid for
aerobic energy.
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Training Heart Rate

• The intensity of work will depend on your level
  of fitness. When training your aerobic system it
  is important to work at an intensity that
  overloads your system, but keeps you below your
  anaerobic threshold.

If you go beyond you anaerobic threshold the
predominant method of producing energy is the
lactic acid system. If you rely heavily on this
system LA will accumulate and cause fatigue.
The training heart rate uses the heart rate that
is equivalent to the percentage of the VO2 max
that the athlete wishes to train at. It can be
estimated by the Karoven method.
To calculate training heart rate equivalent to
75 of VO2 max Training heart rate 75 Heart
rate at rest 0.75 (max heart rate heart rate
at rest)
Rather than use one target heart rate, athletes
tend to use a target heart rate range. So they
calculate an upper limit based on 75 VO2 max and
a lower limit of 60 VO2 max. Athletes start at
lower limit and gradually work up. As the
athletes aerobic capacity increases they will
have to perform at a higher rate of work to reach
the training range. (Shown on the graph).
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ADAPTATIONS PRODUCED BY AEROBIC TRAINING

• Types of aerobic training include Continuous,
  Fartlek and Interval.
• Page 238 Honeybourne et al, Physical Education
  and Sport. Make notes on the body's response to
  aerobic training.

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FUEL FOR EXERCISE

• A BALANCED DIET
• contains proportions of
• carbohydrates, fats and proteins
• minerals, vitamins, water and roughage (fibre)
• needed to maintain good health
• CARBOHYDRATE - 55
• principal energy giver
• FATS - 30
• storage of energy
• another cource of energy
• carrier of fat soluble vitamins
• PROTEIN - 15
• essential for growth, body building and repair

CARBOHYDRATES glucose is absorbed in the small
intestine GLUCOSE is utilised as fuel in the
liver then stored as liver glycogen transported
as glucose in the blood to other tissues (for
example skeletal muscle) used as an immediate
source of energy or converted and stored as
muscle glycogen FATS absorbed as fatty acids or
glycerol in the small intestine FATTY
ACIDS utilised as fuel in the liver stored as
triglycerides in adipose tissue or skeletal
muscle recalled from fat deposits to the
liver converted to glucose (this is a slow
process) enters the Krebs cycle in aerobic
respiration
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FOOD FUEL USAGE DURING EXERCISE
Dependent on exercise intensity and duration AT
REST ATP utilisation slow a mixture of fats and
carbohydrates
INTENSITY LOW / DURATION LONG oxidation of a
mixture of carbohydrates and fats the longer the
exercise the bigger the proportion of ATP
regenerated from fats
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INTENSITY HIGH / DURATION SHORT Rapid and
immediate increase in ATP usage. CP provides ATP
resynthesis muscle and liver glycogen stores
used lactic acid produced.
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FOOD FUEL UTILISATION DURING EXERCISE
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FOOD FUEL UTILISATION DURING AEROBIC EXERCISE
GLYCOGEN SPARING - thereby releasing CHO for
higher intensity work AS A LONG-TERM ADAPTATION
TO AEROBIC TRAINING For the person who has
undertaken sustained aerobic training an
adaptation is produced where fats are used
earlier on in exercise thus conserving glycogen
stores (respiratory exchange ratio (RER)
indicates greater use of fats) the graph shows a
higher proportion of fats utilised by the trained
person
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Glycogen depletion
Explain what happens to a performers glycogen
levels during a triathalon and how this can be
combated.

• Its possible to severely deplete glycogen stores
  while performing prolonged periods of exercise
  like a triathalon. When liver glycogen stores run
  low the blood glucose is used. If blood glucose
  levels drop the athlete can suffer from
  hypoglycaemia. This condition can be avoided if
  the athlete consumes a glucose-based drink during
  the activity.
• Explain the effect that taking a carbohydrate
  drink or snack shortly before exercise will have
  on performance.
• Taking a glucose drink or carb snack shortly
  before the onset of prolonged exercise will
  usually have a negative effect on performance
  because elevated levels of blood glucose result
  in an increase in insulin levels. An increase in
  insulin levels inhibits the enzyme that controls
  the oxidation of fat, so the body will have to
  rely more heavily on the breakdown of carbs,
  depleting stores even quicker.
• Explain what happens to a triathlete if he sets
  off too fast.
• If a triathlete sets off at a faster pace than
  they can cope with they will encounter
  difficulties. This is because during the early
  stages of exercise you rely on the anaerobic
  system and if you work too hard, lactic acid will
  accumulate early in the race. Lactic acid
  inhibits the breakdown of fat, therefore delaying
  the most economical fuel. Another related problem
  is that if you deplete your glycogen stores early
  in an event you may not have enough left to
  produce a sprint for home.

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CARBOLOADING Aims to raise muscle glycogen stores
above their normal resting levels prior to
endurance competitions with over 90 minutes
continuous activity. Suitable for activities
with low anaerobic and high aerobic
components based on Depletion - prolonged
exercise to reduce levels of liver and muscle
glycogen stores - at least seven days before
event Repletion - a high CHO diet in the period
(three to four days) before activity combined
with light exercise or rest Also suitable for
activities lasting 15 - 20 minutes with a two day
high CHO diet beforehand
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Carbohydrate loading (new technique after
Williams 1998) Endurance taper taper taper taper
taper taper training training training
training training training training day
1 day 2 day 3 day 4 day 5 day 6 day 7 race
normal moderate----------------------? high
----------------------------------? diet CHO diet
CHO diet this technique omits the
glycogen depletion phase associated with earlier
methods
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DIETARY MANIPULATION The following graph shows
the influence of dietary carbohydrate on muscle
glycogen stores. Repeated daily exercise of 2
hours is followed by a either a high CHO or low
CHO diet on a low CHO diet, muscle fatigue would
be considerably greater accumulating over a
period of days.
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MUSCLE FATIGUE
MUSCLE FATIGUE a reduction of muscular
performance an inability to maintain expected
power output DEPLETION OF ENERGY
STORES depletion of PC and muscle / liver
glycogen stores fatigue in marathon runners is
due to depletion of muscle glycogen in both ST
and FT fibres FIBRE TYPE FT muscle fibres have
low aerobic capacity therefore quickly fatigue
during maximal activity METABOLIC
ACCUMULATION accumulation of lactic acid and CO2
in muscle cells decrease in pH inhibits enzyme
action (both aerobic and anaerobic) required for
ATP regeneration
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OTHER CAUSES ANTICIPATED FATIGUE the CNS might
perceive fatigue prior to physiological
fatigue BODY FLUID BALANCE fluid loss decreases
plasma volume which reduces blood pressure hence
a reduction in blood flow to skin and
muscles hence the heart has to work harder, body
temperature rises, hence fatigue occurs hence
fluid intake is important during endurance
activities
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TEMPERATURE REGULATION
TEMPERATURE REGULATION The thermoregulatory
center is situated in the hypothalamus. Changes
in body temperature are sensed by central and
peripheral receptors. Body temperature is
maintained by balancing heat input and heat
loss. heat input Metabolic heat Exercise S
hivering heat loss Radiation Conduction C
onvection Evaporation
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TEMPERATURE REGULATION Estimated percentage heat
loss at rest and during exercise mechanism of
heat loss rest total exercise
total conduction convection 20 15 radiation
60 5 evaporation 20 80 During exercise
core temperature increases as a result of an
increase in metabolic heat production and most of
this excess heat is lost via evaporation. Body
size is an important consideration for heat
loss. Subjects who have a small surface
area-to-body mass ratio and more fat are less
susceptible to hypothermia but experience greater
difficulty in dissipating excess heat.
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Exam Question Effective temperature regulation
is vital to the marathon runner. How is body
temperature regulated, and under what conditions
does this process become more difficult? (3
marks)
Thermoregulatory centre/medulla/hypothalamus Exer
cise generates (excessive) heat Needs to be lost
through radiation Vasodilation/ blood closer to
the skin Conduction/convection (sub max 2
marks) Evaporation/sweating Sweating involves
loss of water Dehydration Worse if high
temperatures/ sunny/humidity Need for water
intake during event. (sub marks 2 marks)
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WATER BALANCE (water is 60 of total body
mass) water balance at rest water loss occurs
via evaporation excretion majority lost as
urine water intake depends on climate and body
mass water balance during exercise more water
produced during tissue respiration water loss
mainly as sweat determined by external
temperature, body mass and metabolic
rate increased water loss via expired air due to
increased rate of breathing. kidneys decrease
urine flow in an attempt to decrease
dehydration During a marathon 6-10 of body
water content is lost, hence the need for water
intake during exercise, this means that during 1
hours exercise an average person could expect to
lose around 1 litre of fluid and even more in hot
conditions this could represent as much as 2
litres an hour in warm / humid conditions
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WATER BALANCE

• excessive loss of fluid impairs performance
• as blood plasma volume decreases
• and body temperature rises
• extra strain is placed on the heart, lungs and
  circulatory system
• which means that the heart has to work harder to
  pump blood around the body

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FLUID INTAKE DURING OR IN BETWEEN EXERCISE

• water loss of as little as 2 to 3 can reduce
  performance
• the graph shows how heart rate is affected by
  fluid intake during prolonged exercise
• hence an isotonic sports drink including very
  diluted sodium and glucose content prevents
  dehydration and supplements energy reserves
• or just take water