Energy Systems
Explain the factors that contribute to a performer’s VO2
max. (7 marks)
• VO2 max definition – maximum volume of oxygen that can be utilised
per minute/unit of time
• Relative VO2 max definition – takes into account body weight/ ml.kg1.min-1
• Lifestyle – lack of exercise/smoking/poor diet/fitter/equiv
• Training – continuous/aerobic/fartlek improves VO2 max/stamina/
endurance training
• Age – VO2 max decreases with age
• Physiology – number of slow twitch fibres/capillary density/number of
mitochondria/haemoglobin content/surface area of alveoli/red blood
cell count/efficiency of heart or equivalent
• Genetics – inherited factors of physiology limit possible improvement
• Gender - men generally have approx. 20% higher VO2 max than women
• Body composition – higher percentage of body fat decreases VO2
max/poor diet reduce VO2 max/overweight/obese
Using your knowledge of energy systems, outline and
explain the relationship between energy sources and
intensity of exercise. (7 marks)
A. At low level of exercise energy comes from a mixture of fats and carbohydrates;
B. Broken down aerobically/using oxygen/aerobic system;
C. Glycolysis/Anaerobic Glycolysis – glucose broken down/pyruvic acid/pyruvate
D. Beta oxidation breaks down fats/tri-glycerides/free fatty acids
E. Krebs Cycle – oxidation of acetyl-coenzyme-A/Citric acid production
F. Electron transport/transfer chain – water formed/hydrogen ions/protons used
G. At high levels of intensity carbohydrates are only energy source/as intensity
increases, more carbohydrates used;
H. At high intensity fat use limited by oxygen availability/no fats used
anaerobically/lack of oxygen;
I. Slower energy release from fats/quick release of energy from carbohydrates;
J. (Carbohydrate break down) Lactic Acid System/Lactate anaerobic system
K. No oxygen used/anaerobic
L. Glycolysis/Anaerobic Glycolysis – glucose broken down/pyruvic acid/pyruvate
formed/lactate/lactic acid formed
Explain how the majority of energy is
provided for gymnastic events. (7 marks)
A. Anaerobic/without oxygen
B. (during first few seconds) stored ATP splits/breaks down
initially/ATP breaks down to ADP + P + energy
C. ATP-PC/system/phosphocreatine system/alactic system
D. PC = C + P(i) + energy/creatine + phosphate/PC broken down;
E. Energy used for ATP resynthesis/ADP + P + energy = ATP/ADP +
PC = ATP + C;
F. Lasts 5-10 seconds/limited supply
G. Lactic acid system/Lactate anaerobic system
H. Glycogen/glucose breakdown
I. Glycolysis
J. To pyruvate/pyruvic acid
K. Lactate/lactic acid formed
Outline the function and process of the fast component
of the recovery process. (4 marks)
A. EPOC explanation – volume of oxygen consumed in
recovery above the resting rate
B. The alactacid/alactic (debt/component)
C. Re-saturation of myoglobin/haemoglobin with
D. Re-synthesise ATP/PC levels
E. Uses 2-4 litres of oxygen
F. Completed in 2-3 minutes
G. 50% PC stores replenished within 30 seconds/75%
within 60 seconds
At the 2008 Beijing Olympic Games, David Davies won the silver medal in the
swimming 10 kilometre marathon event, in a time of 1 hour 51 minutes and
53.1 seconds. Explain how the majority of energy used during the race would
be provided. (7 marks)
A. Majority produced by the aerobic system/oxygen
B. Glycolysis/Anaerobic glycolysis
C. Carbohydrates/glycogen/glucose
D. broken down into pyruvate/ pyruvic acid
E. Some ATP produced/2 ATP
F. Krebs cycle
G. Fats/triglycerides/fatty acids/glycerol
H. Beta oxidation
I. Oxidation of acetyl-coenzyme-A/Citric acid/ production of CO2
J. Electron transport chain
K. Water/H2O formed/hydrogen ions formed (H+)/
L. Large quantities of ATP produced or resynthesised/34- 36 ATP
Competitive swimmers will often compete in several events and
suffer from fatigue due to limited recovery time. Explain the
possible causes of fatigue during a race. (3 marks)
A. Build up of lactic acid /accumulation of hydrogen
B. Glycogen depletion/needed for glycolysis
C. Dehydration/reduces blood flow/loss of
electrolytes/increase body temperature
D. Reduced levels of calcium
E. Reduced levels of acetylcholine/slows nerve
impulse and inhibits contraction
F. Lack of PC stores
Elite swimmers follow structured training programme to develop
exceptional levels of fitness. Outline the relationship between
‘VO2 max’ and ‘lactate threshold’. (3 marks)
A. VO2 max – the maximum amount of oxygen utilised/equiv
unit of time/per minute
B. Lactate threshold – the point at which lactic acid starts to
accumulate in the blood/OBLA
C. Lactate threshold is a percentage of VO2max
D. The higher the VO2 max, the more the delay in lactic acid
build-up/as VO2max increases, so does lactate threshold
E. Trained athletes can exercise for longer periods at the
same/higher intensity compared to an untrained
athlete/lactate threshold a much higher percentage of VO2
Explain how lactate is removed from
the blood by the body. (4 marks)
• Used as respiratory substrate/for
respiration/energy/using oxygen (O2)/lactate to
• replenish ATP;
• Converted to pyruvate/pyruvic acid;
• Then to Carbon Dioxide (CO2) and water;
• In inactive muscle and various tissues/organs;
• Converted to glycogen/glucose;
• In liver;
• Some excreted in sweat/urine/conversion to protein
Elite games players require high levels of fitness and psychological preparation,
therefore regular fitness testing and after-match performance analysis are common.
(a) Figure 1 illustrates the relationship between the concentration of blood lactate and
Use Figure 1 to identify the workload level at which lactate threshold occurs, and explain
why lactate (lactic acid) tends to be produced when a player is exercising. (3 marks)
Lactate threshold correctly identified as between 500 and 800 Watts;
Lactate from anaerobic (glycolosis)/lack of oxygen (O2)/high demand/lack of supply;
Greater demand for ATP resynthesis during exercise;
Excess Hydrogen ions produced during glycolysis and Kreb’s cycle;
Join with pyruvate to form lactic acid (when oxygen is no longer available)
High intensity/workload exercise/equiv.
What do you understand by the term lactate
threshold? (2 marks)
• Lactic acid accumulates in blood;
• 2 mmol of lactic acid per litre of blood;
• Exercise has become anaerobic.
Explain how knowing blood lactate levels during a
swim might assist an elite performer. (2 marks)
• 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.
Describe the changes that occur in the body to make the aerobic
energy systems more efficient following prolonged endurance
training. (4 marks
Cardiac hypertrophy
Increased resting stroke volume
Decreased resting heart rate
Increased blood volume and haemoglobin levels
Increased muscle glycogen stores
Increased myoglobin content in muscles
Increased capilliarisation of muscle
Increased number and size of mitochondria
Resulting increase in VO2 max (maximal oxygen
The triathlon is an athletic event that involves
performers undertaking a long distance swim,
immediately followed by a cycle race and then
finally a run of several kilometres.
(a) What would be the major energy sources used
by a triathlete? (3 marks)
(b) Briefly explain how these energy sources are
used for regeneration of ATP. (5 marks)
1. Fats; 2. Fatty acids; 3. Glycerol;
5. Carbohydrates;
6. Glycogen;
4. Triglycerides.
7. Glucose;
8. Protein/lactate.
1. Carbohydrates/glycogen/glucose broken down into pyruvate;
2. Anaerobic/glycolysis;
3. Some ATP produced;
4. Fats/triglycerides/fatty acids/glycerol broken down into variety of
5. Beta oxidation;
6. Into mitochondria;
7. Krebs cycle;
8. Electron transport chain;
9. Oxidation/aerobic;
10. Large quantities of ATP produced.
(i) Describe and explain the effects of a two-hour
period of intense exercise and recovery periods on
the levels of glycogen in the elite performer.
(4 marks)
(ii) How might this elite performer prepare for a
competition that will last longer than 2 hours?
(3 marks)
1. Glycogen levels decrease during training and restored during recovery
2. Above resting;
3. It takes 24 hours to recover;
4. Glycogen used for energy/ATP formation/production;
5. Aerobic/oxygen;
6. Mitochondria/Kreb’s cycle/pyruvate;
7. Supercompensation/overcompensation/adaptation;
(4 marks)
1. Carboloading/glycogen loading/supercompensate/overcompensate/
glycoloading ;
2. Dietary restriction of carbohydrate;
3. Modified training programme/tapering;
4. Increase carbohydrate intake 24hrs prior to event
5. To store more glycogen than normal;
6. Carbohydrate intake during event;
(3 marks)
It has been said that the winner of a 100m race is the runner
who slows down the least. Explain, using your knowledge of
energy systems, why this might be the case. (7 marks)
• Predominant energy system used in 100m race is ATP-PC
• ATP stores only supply energy for 2-3 seconds.
• PC stores only supply energy for 5-8 seconds.
• Speed of muscle contractions and therefore runners speed will
decrease when ATP-PC stores are depleted.
• Once ATP-PC stores have been depleted the predominant
energy system will be the anaerobic (lactic acid) system.
• This system produces energy at a slower rate and runner will
slow down.
• Athletes who can continue for longer before resorting to the
lactic acid sytem will maintain top speed for longer.
• Training allows the ATP-PC to become more efficient, supplying
energy for a greater period of time.
Research has been conducted into activity cycles of intermittent
sports such as soccer, hockey and rugby, which are reliant on
efficient energy systems.
a) Identify the principle energy source for each of
the following activity cycles in these types of
physical activities:
(i) Walking
(ii) Sprinting
(iii) Jogging
(4 marks)
b) What are the disadvantages of using fat as an
energy source during exercise? (3 marks)
(i) Fats
(ii) Glucose / phosphocreatine
(iii) Fats / glucose
• Extra weight requires greater amounts energy to be produced for
• Reduces flexibility.
• Fat can only be used as an energy source when oxygen is present /
requires oxygen to be broken down / only used during aerobic activity.
• Excess fat causes overheating and problems associated with this
(dehydration, cardiovascular drift etc)
• Cannot be used during explosive activities.
What do you understand by the term VO2
max? (2 marks)
• Max amount of oxygen that can be consumed
and used by the body per minute.
• Greater VO2 max means greater aerobic
fitness / capacity.
• Predominantly genetically determined.
During a game of hockey a performer accumulates a
lactic acid concentration of 8 mmol. Two minutes later
in the game their lactate concentration is 4.8 mmol.
a) Suggest reasons why the performer’s level of
lactic acid had risen to 8 mmol. (4 marks)
b) Give an explanation as to why their lactate
concentration had fallen two minutes later.
(3 marks)
Increased energy requirement due to high intensity of activity.
Anaerobic energy systems used.
Insufficient oxygen available due to high intensity of activity.
Excess Hydrogen produced during breakdown of glucose in glycolysis and
Kreb’s cycle.
• Joins with pyruvate when oxygen no longer available.
• Forms lactic acid.
• Lactate threshold (2 mmol) and OBLA (4 mmol) passed as lactic acid
• Levels may have dropped due to decrease in exercise intensity / break in
• Reduced requirement for ATP resynthesis.
• Reduced levels of Hydrogen being produced reduces the production of lactic
• Slow component of EPOC (lactacid component).
• Oxidation of lactic acid into carbon dioxide and water (and pyruvate) to
continue through Kreb’s cycle.
An 800m runner undertakes aerobic training to improve their VO2 max.
Why might this improve their 800m personal best? (7 marks)
• VO2 max is the maximum amount of O2 that can be consumed and
used in one minute.
• Greater VO2 max means more O2 available for aerobic energy
• Allows for greater use of fats as an energy source thus saving
glucose stores for later in the race.
• More energy produced aerobically reduces reliance on anaerobic
systems and therefore delays lactate threshold.
• Hydrogen produced during glycolysis and Kreb’s cycle joins with
oxygen rather than joining pyruvate to form lactic acid.
• Prevents build up of lactic acid which would hinder energy
• Greater availability of O2 helps to speed up EPOC.
• This results in faster resynthesis of ATP and PC stores.
• Allows for sprint finish.
After a period of intense exercise a performer shows
evidence of heightened ventilation rate and heart rate
two minutes after the end of exercise.
a) In terms of recovery, why does the performer
exhibit these raised heart and ventilation
rates? (4 marks)
b) Why should the organisers of world
championship athletics meetings allow at
least three days between 1500m races? Use
your knowledge of recovery in your answer.
(3 marks)
• Increased heart rate and ventilation rate to increase supply of oxygen
to working muscles.
• O2 required for EPOC.
• Fast (alactacid) component of EPOC involves reloading myoglobin with
• Also replenishes ATP and PC stores.
• 50% of PC stores replenished within one minute, 100% within 3-4 mins.
• Increased O2 supply also involved in conversion of lactic acid back into
pyruvate (and water) to rejoin Kreb’s cycle as an energy source.
• Slow (lactacid) component of EPOC requires time to deal with excess
lactic acid.
• Lactic acid can be converted to pyruvate and water / glycogen / protein
/ glucose.
• Time is needed to replenish glucose stores depleted from a 1500m
• Muscle cells need time for repair after 1500m race.

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