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.