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HMS, BM 2017 HSC 25

Compare TWO different energy systems by exploring their duration, sources of fuel and causes of fatigue. Use examples to support your answer.   (7 marks)

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Energy Systems Being Compared:

  • ATP-PCr System (Phosphocreatine System)
  • Aerobic System (Oxidative System)

Similarities

  • Both energy systems produce ATP to fuel muscle contractions during exercise activities. They work together seamlessly during most physical activities to meet energy demands.
  • Both systems can operate without requiring external oxygen supply from the respiratory system. This allows immediate energy production when exercise begins before breathing rate increases.

Differences – Duration

  • The ATP-PCr system operates for very short durations of 10-15 seconds maximum. This occurs because stored ATP and creatine phosphate supplies are limited in muscle cells.
  • The aerobic system functions for hours or even days. This happens because oxygen allows continuous fuel breakdown without harmful byproduct accumulation.

Differences – Fuel Sources

  • The ATP-PCr system sources fuel from stored ATP and creatine phosphate already present in muscles. This enables immediate energy release without requiring glucose breakdown.
  • The aerobic system utilises carbohydrates, fats and proteins as fuel sources.  This process requires oxygen to completely break down these substrates.

Differences – Causes of Fatigue

  • Fatigue in the ATP-PCr system results from depletion of stored phosphocreatine reserves. For instance, a weightlifter cannot continue once stores are exhausted.
  • Aerobic system fatigue occurs due to fuel depletion or oxygen limitations. Marathon runners experience this when glycogen stores become depleted.
Show Worked Solution

Energy Systems Being Compared:

  • ATP-PCr System (Phosphocreatine System)
  • Aerobic System (Oxidative System)

Similarities

  • Both energy systems produce ATP to fuel muscle contractions during exercise activities. They work together seamlessly during most physical activities to meet energy demands.
  • Both systems can operate without requiring external oxygen supply from the respiratory system. This allows immediate energy production when exercise begins before breathing rate increases.

Differences – Duration

  • The ATP-PCr system operates for very short durations of 10-15 seconds maximum. This occurs because stored ATP and creatine phosphate supplies are limited in muscle cells.
  • The aerobic system functions for hours or even days. This happens because oxygen allows continuous fuel breakdown without harmful byproduct accumulation.

Differences – Fuel Sources

  • The ATP-PCr system sources fuel from stored ATP and creatine phosphate already present in muscles. This enables immediate energy release without requiring glucose breakdown.
  • The aerobic system utilises carbohydrates, fats and proteins as fuel sources.  This process requires oxygen to completely break down these substrates.

Differences – Causes of Fatigue

  • Fatigue in the ATP-PCr system results from depletion of stored phosphocreatine reserves. For instance, a weightlifter cannot continue once stores are exhausted.
  • Aerobic system fatigue occurs due to fuel depletion or oxygen limitations. Marathon runners experience this when glycogen stores become depleted.

♦♦ Mean mark 55%.

HMS, BM 2020 HSC 23

An athlete ran in the 100-metre final at an Olympic Games.

  1. In the table below, identify the predominant energy system used by the athlete,
    and the features of that energy system.   (3 marks)

    Predominant energy system used by this athlete  
    Source of fuel  
    Energy system duration  
    Cause of fatigue  
    Rate of recovery  
  2. Compare how anxiety and arousal may have affected the athlete’s performance
    when competing in this 100-metre final. Provide examples to support your
    answer.   (4 marks)

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a.   
 Predominant energy system used by this athlete ATP-PCr system (Alactacid system)
  Source of fuel Creatine phosphate (CP)
  Energy system duration 6-12 seconds
  Cause of fatigue Depletion of creatine phosphate stores
  Rate of recovery 2-3 minutes for complete recovery

b.    Similarities:

  • Both anxiety and arousal can negatively impact the sprinter’s performance if levels become too high.
  • Both factors influence the athlete’s ability to execute optimal technique and can cause muscle tension that restricts smooth movement patterns during the race.

Differences:

  • Anxiety is a psychological state involving fear and worry about competitive outcome. High anxiety may cause the sprinter to overthink race strategy, leading to delayed reaction time from starting blocks and mental distraction affecting stride mechanics.
  • Arousal refers to physiological activation levels. Optimal arousal enhances alertness and muscle readiness for explosive starts. However, excessive arousal creates physical tension that reduces stride length and power output through restricted movement patterns.
Show Worked Solution
a.   
 Predominant energy system used by this athlete ATP-PCr system (Alactacid system)
  Source of fuel Creatine phosphate (CP)
  Energy system duration 6-12 seconds
  Cause of fatigue Depletion of creatine phosphate stores
  Rate of recovery 2-3 minutes for complete recovery

b.    Similarities:

  • Both anxiety and arousal can negatively impact the sprinter’s performance if levels become too high.
  • Both factors influence the athlete’s ability to execute optimal technique and can cause muscle tension that restricts smooth movement patterns during the race.

Differences:

  • Anxiety is a psychological state involving fear and worry about competitive outcome. High anxiety may cause the sprinter to overthink race strategy, leading to delayed reaction time from starting blocks and mental distraction affecting stride mechanics.
  • Arousal refers to physiological activation levels. Optimal arousal enhances alertness and muscle readiness for explosive starts. However, excessive arousal creates physical tension that reduces stride length and power output through restricted movement patterns.

♦♦ Mean mark 49%.

HMS, BM EQ-Bank 763

Analyse how the availability of different fuel sources influences energy system dominance and fatigue during a 1500-metre running race.   (8 marks)

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Sample Answer

Overview Statement

  • Fuel availability determines energy system dominance throughout the 1500m race.
  • Phosphocreatine, glucose and oxygen availability interact to shape pacing and fatigue patterns.

PCr Availability and Sprint Performance

  • Limited phosphocreatine stores enable explosive acceleration for only 10-15 seconds at the start.
  • This leads to rapid PCr depletion, forcing reliance on glycolytic system by the first curve.
  • PCr partially replenishes during the middle laps, allowing a final sprint if managed correctly.
  • Therefore, PCr availability dictates tactical positioning opportunities throughout the race.

Glucose Supply and Sustained Speed

  • Abundant muscle glucose supports high-intensity running through anaerobic glycolysis after PCr depletion.
  • This process generates lactic acid accumulation, which progressively impairs muscle contraction efficiency.
  • The glycolytic system depends on glucose availability but is limited by rising acidity, not fuel depletion.
  • Consequently, glucose availability permits sustained speed while lactic acid constrains maximum effort duration.

Oxygen and Aerobic Contribution

  • Increasing oxygen uptake enables aerobic metabolism to contribute more ATP as the race progresses.
  • The aerobic system utilises glucose more efficiently than glycolysis, producing more ATP per glucose molecule.
  • This efficiency allows sustained pace during middle laps while preserving some glucose for the finish.
  • Thus, oxygen availability determines the balance between efficient and inefficient fuel use.

Implications and Synthesis

  • Fuel availability creates a hierarchy: PCr exhausts first, glucose remains adequate, oxygen increases gradually.
  • This pattern means energy systems shift from ATP-PCr to glycolytic to increasingly aerobic dominance.
  • Fatigue results from PCr depletion initially, then lactic acid accumulation, rather than fuel exhaustion.
  • Therefore, understanding fuel availability reveals why pacing strategies must match energy system capabilities.
Show Worked Solution

Sample Answer

Overview Statement

  • Fuel availability determines energy system dominance throughout the 1500m race.
  • Phosphocreatine, glucose and oxygen availability interact to shape pacing and fatigue patterns.

PCr Availability and Sprint Performance

  • Limited phosphocreatine stores enable explosive acceleration for only 10-15 seconds at the start.
  • This leads to rapid PCr depletion, forcing reliance on glycolytic system by the first curve.
  • PCr partially replenishes during the middle laps, allowing a final sprint if managed correctly.
  • Therefore, PCr availability dictates tactical positioning opportunities throughout the race.

Glucose Supply and Sustained Speed

  • Abundant muscle glucose supports high-intensity running through anaerobic glycolysis after PCr depletion.
  • This process generates lactic acid accumulation, which progressively impairs muscle contraction efficiency.
  • The glycolytic system depends on glucose availability but is limited by rising acidity, not fuel depletion.
  • Consequently, glucose availability permits sustained speed while lactic acid constrains maximum effort duration.

Oxygen and Aerobic Contribution

  • Increasing oxygen uptake enables aerobic metabolism to contribute more ATP as the race progresses.
  • The aerobic system utilises glucose more efficiently than glycolysis, producing more ATP per glucose molecule.
  • This efficiency allows sustained pace during middle laps while preserving some glucose for the finish.
  • Thus, oxygen availability determines the balance between efficient and inefficient fuel use.

Implications and Synthesis

  • Fuel availability creates a hierarchy: PCr exhausts first, glucose remains adequate, oxygen increases gradually.
  • This pattern means energy systems shift from ATP-PCr to glycolytic to increasingly aerobic dominance.
  • Fatigue results from PCr depletion initially, then lactic acid accumulation, rather than fuel exhaustion.
  • Therefore, understanding fuel availability reveals why pacing strategies must match energy system capabilities.

HMS, BM EQ-Bank 762

How does the depletion of fuel sources in the aerobic energy system contribute to an athlete "hitting the wall" during a marathon at around the 32-kilometre mark?   (5 marks)

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Sample Answer

  • Marathon runners begin by using both carbohydrate and fat for fuel, with glycogen providing easy energy at steady pace.
  • After about 2 hours, muscle glycogen stores run very low, which forces the body to use mainly fat for energy.
  • Fat needs more oxygen to make ATP than carbohydrate does, resulting in higher oxygen demands that the body cannot meet at the same running speed.
  • This change causes runners to slow down immediately as their bodies cannot get enough oxygen for the pace.
  • Body temperature goes up because fat burning is less efficient, creating extra heat that makes runners feel hotter.
  • Breathing rate increases to get more oxygen for fat burning, which makes runners feel breathless even though they’ve slowed down.
  • The brain also lacks glucose, causing poor concentration and less motivation to continue.
  • These problems together create the sudden tiredness known as “hitting the wall”.
  • Therefore, glycogen depletion forces the body to use harder-to-burn fat for fuel.
Show Worked Solution

Sample Answer

  • Marathon runners begin by using both carbohydrate and fat for fuel, with glycogen providing easy energy at steady pace.
  • After about 2 hours, muscle glycogen stores run very low, which forces the body to use mainly fat for energy.
  • Fat needs more oxygen to make ATP than carbohydrate does, resulting in higher oxygen demands that the body cannot meet at the same running speed.
  • This change causes runners to slow down immediately as their bodies cannot get enough oxygen for the pace.
  • Body temperature goes up because fat burning is less efficient, creating extra heat that makes runners feel hotter.
  • Breathing rate increases to get more oxygen for fat burning, which makes runners feel breathless even though they’ve slowed down.
  • The brain also lacks glucose, causing poor concentration and less motivation to continue.
  • These problems together create the sudden tiredness known as “hitting the wall”.
  • Therefore, glycogen depletion forces the body to use harder-to-burn fat for fuel.

HMS, BM EQ-Bank 761

Describe how fuel sources contribute to fatigue during the final stretch of a 400-metre race.  (3 marks)

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Sample Answer

  • The 400m relies heavily on the glycolytic system which uses glucose as fuel for the final stretch.
  • This system produces ATP quickly but creates lactic acid as a by-product.
  • Lactic acid builds up rapidly in muscles, making them increasingly acidic and reducing their ability to contract.
  • Additionally, the intense effort uses up muscle glucose stores quickly.
  • These combined effects cause severe fatigue, forcing runners to slow dramatically in the final metres.
Show Worked Solution

Sample Answer

  • The 400m relies heavily on the glycolytic system which uses glucose as fuel for the final stretch.
  • This system produces ATP quickly but creates lactic acid as a by-product.
  • Lactic acid builds up rapidly in muscles, making them increasingly acidic and reducing their ability to contract.
  • Additionally, the intense effort uses up muscle glucose stores quickly.
  • These combined effects cause severe fatigue, forcing runners to slow dramatically in the final metres.

HMS, BM EQ-Bank 760

Evaluate the importance of different fuel sources and their efficiency of ATP production for athletes competing in different duration events.   (8 marks)

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Sample Answer

Evaluation Statement

  • Fuel source selection and ATP production efficiency fundamentally determine athletic performance across different event durations.
  • Evaluation based on: fuel availability, ATP yield efficiency, and event-specific demands.

Short Duration Events (10-15 seconds)

  • Phosphocreatine provides the only fuel source for explosive efforts like shot put or 100m sprint starts.
  • This system produces ATP most rapidly, enabling maximum power output immediately.
  • However, limited PCr stores exhaust within seconds, making it unsuitable for longer efforts.
  • The trade-off between speed and capacity proves ideal for brief maximal performances.

Medium Duration Events (30 seconds – 2 minutes)

  • Glucose becomes the primary fuel through anaerobic breakdown during 400m runs or 100m swims.
  • This produces ATP quickly but inefficiently, with only partial glucose breakdown occurring.
  • Lactic acid accumulation limits duration despite adequate glucose availability.
  • Athletes must balance intensity against rapidly increasing fatigue from metabolic by-products.

Long Duration Events (over 3 minutes)

  • Both carbohydrates and fats fuel aerobic metabolism in marathons and distance cycling.
  • Complete fuel oxidation yields far more ATP per glucose molecule than anaerobic systems.
  • Fat provides virtually unlimited energy but requires more oxygen per ATP produced.
  • Efficiency allows sustained performance though at lower intensities than anaerobic metabolism permits.

Final Evaluation

  • Event duration dictates optimal fuel source selection more than any other factor.
  • ATP production efficiency inversely relates to production speed across all systems.
  • Athletes cannot choose their fuel source; duration and intensity determine it automatically.
  • Understanding these relationships helps athletes pace efforts appropriately for their event.
Show Worked Solution

Sample Answer 

Evaluation Statement

  • Fuel source selection and ATP production efficiency fundamentally determine athletic performance across different event durations.
  • Evaluation based on: fuel availability, ATP yield efficiency, and event-specific demands.

Short Duration Events (10-15 seconds)

  • Phosphocreatine provides the only fuel source for explosive efforts like shot put or 100m sprint starts.
  • This system produces ATP most rapidly, enabling maximum power output immediately.
  • However, limited PCr stores exhaust within seconds, making it unsuitable for longer efforts.
  • The trade-off between speed and capacity proves ideal for brief maximal performances.

Medium Duration Events (30 seconds – 2 minutes)

  • Glucose becomes the primary fuel through anaerobic breakdown during 400m runs or 100m swims.
  • This produces ATP quickly but inefficiently, with only partial glucose breakdown occurring.
  • Lactic acid accumulation limits duration despite adequate glucose availability.
  • Athletes must balance intensity against rapidly increasing fatigue from metabolic by-products.

Long Duration Events (over 3 minutes)

  • Both carbohydrates and fats fuel aerobic metabolism in marathons and distance cycling.
  • Complete fuel oxidation yields far more ATP per glucose molecule than anaerobic systems.
  • Fat provides virtually unlimited energy but requires more oxygen per ATP produced.
  • Efficiency allows sustained performance though at lower intensities than anaerobic metabolism permits.

Final Evaluation

  • Event duration dictates optimal fuel source selection more than any other factor.
  • ATP production efficiency inversely relates to production speed across all systems.
  • Athletes cannot choose their fuel source; duration and intensity determine it automatically.
  • Understanding these relationships helps athletes pace efforts appropriately for their event.

HMS, BM EQ-Bank 759

A netball centre typically performs high-intensity bursts of activity throughout a 60-minute game. Describe how the fuel sources used by this athlete would change during different phases of the game.   (6 marks)

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Sample Answer

  • During explosive movements (jumping, quick directional changes), the centre primarily uses phosphocreatine through the ATP-PCr system for immediate energy.
  • In fast breaks or intense rallies lasting 10-30 seconds, the glycolytic system becomes dominant, using muscle glycogen and blood glucose as fuel sources.
  • During lower intensity periods of the game, the aerobic system predominates, using carbohydrates as the primary fuel source.
  • As the game progresses and glycogen stores become partially depleted, the body increases its reliance on fat metabolism during recovery phases between high-intensity efforts.
  • The interplay of energy systems allows the centre to perform repeated high-intensity efforts throughout the game by recovering phosphocreatine stores during periods of lower intensity.
  • The athlete’s ability to spare glycogen through efficient use of fats during lower intensity phases helps maintain carbohydrate availability for high-intensity efforts in the latter stages of the game.
Show Worked Solution

Sample Answer 

  • During explosive movements (jumping, quick directional changes), the centre primarily uses phosphocreatine through the ATP-PCr system for immediate energy.
  • In fast breaks or intense rallies lasting 10-30 seconds, the glycolytic system becomes dominant, using muscle glycogen and blood glucose as fuel sources.
  • During lower intensity periods of the game, the aerobic system predominates, using carbohydrates as the primary fuel source.
  • As the game progresses and glycogen stores become partially depleted, the body increases its reliance on fat metabolism during recovery phases between high-intensity efforts.
  • The interplay of energy systems allows the centre to perform repeated high-intensity efforts throughout the game by recovering phosphocreatine stores during periods of lower intensity.
  • The athlete’s ability to spare glycogen through efficient use of fats during lower intensity phases helps maintain carbohydrate availability for high-intensity efforts in the latter stages of the game.

HMS, BM EQ-Bank 758

Compare and contrast the efficiency of ATP production in the three energy systems and explain how this affects the duration and intensity of activities where each system is predominant.   (6 marks)

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Sample Answer

  • ATP-PCr system produces ATP rapidly but has limited stores (approximately 90g of ATP and 120g of PCr), allowing only 10-15 seconds of high-intensity activity.
  • The glycolytic system produces ATP at a moderate rate by partially breaking down glucose anaerobically, supporting 30-45 seconds of high-intensity activity.
  • The aerobic system produces ATP efficiently but more slowly, enabling sustained energy production for activities lasting minutes to hours.
  • The ATP-PCr system supports maximal intensity (>95% of maximum heart rate) activities due to rapid ATP production, but quickly fatigues due to limited PCr stores.
  • The glycolytic system supports high, sub-maximal intensity (85-95% of maximum heart rate) activities but accumulates lactic acid, limiting duration to approximately 30 seconds at peak output.
  • The aerobic system supports sub-maximal intensity (\(\leq\)85% of maximum heart rate) activities due to its efficiency in completely metabolising fuels with oxygen, allowing for sustained energy production.
  • The interplay between rate of ATP production and total ATP production capacity determines the specific performance profile of each energy system.
  • The inverse relationship between ATP production rate and total capacity determines each system’s optimal application to specific activity demands.
Show Worked Solution

Sample Answer 

  • ATP-PCr system produces ATP rapidly but has limited stores (approximately 90g of ATP and 120g of PCr), allowing only 10-15 seconds of high-intensity activity.
  • The glycolytic system produces ATP at a moderate rate by partially breaking down glucose anaerobically, supporting 30-45 seconds of high-intensity activity.
  • The aerobic system produces ATP efficiently but more slowly, enabling sustained energy production for activities lasting minutes to hours.
  • The ATP-PCr system supports maximal intensity (>95% of maximum heart rate) activities due to rapid ATP production, but quickly fatigues due to limited PCr stores.
  • The glycolytic system supports high, sub-maximal intensity (85-95% of maximum heart rate) activities but accumulates lactic acid, limiting duration to approximately 30 seconds at peak output.
  • The aerobic system supports sub-maximal intensity (\(\leq\)85% of maximum heart rate) activities due to its efficiency in completely metabolising fuels with oxygen, allowing for sustained energy production.
  • The interplay between rate of ATP production and total ATP production capacity determines the specific performance profile of each energy system.
  • The inverse relationship between ATP production rate and total capacity determines each system’s optimal application to specific activity demands.

HMS, BM EQ-Bank 757

Identify the fuel sources used by the three energy systems and explain why each energy system uses its particular fuel source(s).   (6 marks)

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Sample Answer

  • The ATP-PCr system uses phosphocreatine as fuel because PCr can rapidly donate a phosphate group to ADP to reform ATP without requiring oxygen.
  • The glycolytic (lactic acid) system uses carbohydrates in the form of glucose (from blood) and glycogen (stored in muscles) because these can be quickly broken down anaerobically to produce ATP.
  • The aerobic system can use carbohydrates, fats, and proteins as fuel sources because oxygen is available for complete breakdown of these nutrients through cellular respiration pathways.
  • PCr is used for the ATP-PCr system due to its high concentration in muscle cells (five times that of ATP) allowing for quick energy availability.
  • Carbohydrates are the only fuel source that can be metabolised without oxygen, making them essential for the glycolytic system during high-intensity activities.
  • The aerobic system’s ability to use multiple fuel sources, particularly fat during lower intensities, allows for sustained energy production during prolonged activities when oxygen supply meets demand.
Show Worked Solution

Sample Answer 

  • The ATP-PCr system uses phosphocreatine as fuel because PCr can rapidly donate a phosphate group to ADP to reform ATP without requiring oxygen.
  • The glycolytic (lactic acid) system uses carbohydrates in the form of glucose (from blood) and glycogen (stored in muscles) because these can be quickly broken down anaerobically to produce ATP.
  • The aerobic system can use carbohydrates, fats, and proteins as fuel sources because oxygen is available for complete breakdown of these nutrients through cellular respiration pathways.
  • PCr is used for the ATP-PCr system due to its high concentration in muscle cells (five times that of ATP) allowing for quick energy availability.
  • Carbohydrates are the only fuel source that can be metabolised without oxygen, making them essential for the glycolytic system during high-intensity activities.
  • The aerobic system’s ability to use multiple fuel sources, particularly fat during lower intensities, allows for sustained energy production during prolonged activities when oxygen supply meets demand.

HMS, BM EQ-Bank 756 MC

During a marathon, which statement accurately describes what happens to an athlete's fuel usage after approximately 2 hours of running?

  1. The athlete continues to rely exclusively on the ATP-PCr system
  2. The glycolytic system becomes the predominant energy provider
  3. The body shifts from predominantly using glycogen to using more fat
  4. Protein becomes the primary fuel source for ATP production
Show Answers Only

\(C\)

Show Worked Solution
  • C is correct:
    • During a marathon, after approximately 2 hours of running, glycogen stores become depleted.
    • This causes the body to shift from predominantly using glycogen to increasingly relying on fat as a fuel source.

Other Options:

  • A is incorrect: The ATP-PCr system is only predominant for activities lasting 1-10 seconds, not endurance events like marathons.
  • B is incorrect: The glycolytic system is dominant for activities lasting 30-45 seconds, not for prolonged endurance events.
  • D is incorrect: While protein can be used as a fuel source in the aerobic system, it is not the primary fuel source, even in prolonged exercise; fat becomes the primary alternative fuel once glycogen is depleted.

HMS, BM EQ-Bank 755 MC

During a 100-metre sprint, an athlete primarily uses which energy system and fuel source in the first 2 seconds?

  1. ATP-PCr system using phosphocreatine
  2. Glycolytic system using glucose
  3. Aerobic system using carbohydrates
  4. Aerobic system using fats
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\(A\)

Show Worked Solution
  • A is correct:
    • In the first 2 seconds of a 100-metre sprint, the body relies on the ATP-PCr system.
    • This system uses phosphocreatine as its fuel source to rapidly generate ATP for the explosive muscular contraction needed at the start of the sprint.

Other Options:

  • B is incorrect: The glycolytic system becomes predominant after approximately 10 seconds once PCr supplies begin to deplete.
  • C is incorrect: The aerobic system using carbohydrates is not the predominant energy system during the initial explosive phase of a sprint.
  • D is incorrect: The aerobic system using fats is used primarily during longer duration, lower intensity activities, not the explosive start of a sprint.

HMS, BM EQ-Bank 151

Analyse how the availability of different fuel sources affects an athlete's performance in a 90-minute soccer match.   (6 marks)

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Sample Answer

  • The ATP-PCr system provides immediate energy for explosive sprints and tackles in the first few seconds of each high-intensity effort through stored creatine phosphate.
  • During the match, muscle glycogen serves as the primary fuel source, supporting both aerobic activity for general play and anaerobic bursts for sprinting or rapid directional changes.
  • As the match progresses and muscle glycogen becomes depleted, the body increasingly relies on fatty acid oxidation for energy production during lower intensity periods of play.
  • The maintenance of blood glucose levels through liver glycogen breakdown becomes crucial in the latter stages of the match to sustain both physical and mental performance.
  • Players often experience fatigue in the final 15 – 20 minutes of the match due to significant depletion of muscle glycogen stores, resulting in reduced sprint capacity and skill execution.
  • Athletes who engage in carbohydrate loading protocols prior to the match can increase their muscle glycogen stores by up to 50%, thereby delaying the onset of fatigue and maintaining performance intensity throughout the full 90 minutes.
Show Worked Solution

Sample Answer

  • The ATP-PCr system provides immediate energy for explosive sprints and tackles in the first few seconds of each high-intensity effort through stored creatine phosphate.
  • During the match, muscle glycogen serves as the primary fuel source, supporting both aerobic activity for general play and anaerobic bursts for sprinting or rapid directional changes.
  • As the match progresses and muscle glycogen becomes depleted, the body increasingly relies on fatty acid oxidation for energy production during lower intensity periods of play.
  • The maintenance of blood glucose levels through liver glycogen breakdown becomes crucial in the latter stages of the match to sustain both physical and mental performance.
  • Players often experience fatigue in the final 15 – 20 minutes of the match due to significant depletion of muscle glycogen stores, resulting in reduced sprint capacity and skill execution.
  • Athletes who engage in carbohydrate loading protocols prior to the match can increase their muscle glycogen stores by up to 50%, thereby delaying the onset of fatigue and maintaining performance intensity throughout the full 90 minutes.

HMS, BM EQ-Bank 150

Explain how glucose is used differently as a fuel source in the glycolytic and aerobic energy systems.   (4 marks)

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Sample Answer

Glycolytic System:

  • Breaks down glucose without oxygen in sarcoplasm
  • Produces 2 – 3 ATP molecules through rapid glycolysis
  • Results in lactic acid as by-product
  • Powers high-intensity exercise 10 – 60 seconds

Aerobic System:

  • Complete glucose breakdown with oxygen in mitochondria
  • Produces 36 – 38 ATP through Krebs cycle/electron transport chain
  • Results in CO2 and H2O as by-products
  • Powers prolonged exercise 2+ minutes

Summary

  • Glycolytic system sacrifices ATP yield for speed, while aerobic system maximises ATP production through complete glucose oxidation.
Show Worked Solution

Sample Answer

Glycolytic System:

  • Breaks down glucose without oxygen in sarcoplasm
  • Produces 2 – 3 ATP molecules through rapid glycolysis
  • Results in lactic acid as by-product
  • Powers high-intensity exercise 10 – 60 seconds

Aerobic System:

  • Complete glucose breakdown with oxygen in mitochondria
  • Produces 36 – 38 ATP through Krebs cycle/electron transport chain
  • Results in CO2 and H2O as by-products
  • Powers prolonged exercise 2+ minutes

Summary

  • Glycolytic system sacrifices ATP yield for speed, while aerobic system maximises ATP production through complete glucose oxidation.

HMS, BM EQ-Bank 149 MC

Which statement best describes why fatty acids cannot be the primary fuel source for high-intensity exercise?

  1. Fatty acids require too much oxygen for breakdown
  2. Fatty acids are not stored in muscle tissue
  3. Fatty acids produce less ATP than glucose
  4. Fatty acids are too complex to break down quickly
Show Answers Only

\(A\)

Show Worked Solution
  • A is correct: Fatty acid metabolism requires significant oxygen

Other Options:

  • B is incorrect: Fatty acids are stored as intramuscular triglycerides
  • C is incorrect: Fatty acids actually produce more ATP than glucose
  • D is incorrect: Complexity isn’t the primary limitation

HMS, BM EQ-Bank 148 MC

A marathon runner hits "the wall" after 30 kilometres of running. Which fuel source has most likely been depleted?

  1. Creatine phosphate
  2. Blood glucose
  3. Muscle glycogen
  4. Plasma proteins
Show Answers Only

\(C\)

Show Worked Solution
  • C is correct: Muscle glycogen depletion occurs in prolonged exercise

Other Options:

  • A is incorrect: CP depletion occurs in seconds
  • B is incorrect: Blood glucose is maintained through liver glycogen
  • D is incorrect: Proteins are not a primary fuel source

HMS, BM EQ-Bank 144 MC

Which row correctly identifies the fuel source and duration of the ATP-PCr energy system?

\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{B.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\
\end{array}
\begin{array}{|l|l|}
\hline
\rule{0pt}{2.5ex}\textbf{Fuel Source}\rule[-1ex]{0pt}{0pt}& \textbf{Duration} \\
\hline
\rule{0pt}{2.5ex}\text{Glucose}\rule[-1ex]{0pt}{0pt}&\text{30 - 60 seconds}\\
\hline
\rule{0pt}{2.5ex}\text{Creatine Phosphate}\rule[-1ex]{0pt}{0pt}& \text{0 - 10 seconds}\\
\hline
\rule{0pt}{2.5ex}\text{Fatty Acids}\rule[-1ex]{0pt}{0pt}& \text{2+ minutes} \\
\hline
\rule{0pt}{2.5ex}\text{Creatine Phosphate}\rule[-1ex]{0pt}{0pt}& \text{30 - 60 seconds} \\
\hline
\end{array}
\end{align*}

Show Answers Only

\(B\)

Show Worked Solution
  • B is correct: CP is the fuel source and system operates 0 – 10 seconds

Other Options:

  • A is incorrect: Glucose is fuel for glycolytic system
  • C is incorrect: Fatty acids fuel aerobic system
  • D is incorrect: Duration is wrong for ATP-PCr system