Explain how the three energy systems interplay during a 400 metre sprint race. (6 marks)
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Sample Answer
First 2-3 seconds:
- The ATP-PCr system provides immediate energy through rapid breakdown of stored phosphocreatine, enabling explosive acceleration from starting blocks without oxygen requirement.
Seconds 3-15:
- ATP-PCr system remains dominant but begins depleting, with the runner achieving peak velocity as this system provides the highest rate of ATP production for maximum power output.
Seconds 15-30:
- Glycolytic system becomes predominant as ATP-PCr stores deplete, breaking down muscle glycogen to produce ATP anaerobically, resulting in rapid lactic acid formation.
Seconds 30-45:
- Continued dominance of glycolytic system with increasing aerobic contribution as oxygen becomes more available, though anaerobic glycolysis still provides majority of energy.
Final 15 seconds:
- All three systems operate simultaneously with glycolytic system still dominant, but accumulating lactic acid begins interfering with muscle contraction, causing performance decline.
System integration:
- The transition between systems is gradual rather than distinct, with optimal 400 metre performance requiring efficient switching between energy pathways and the ability to tolerate high lactate levels.
Recovery phase:
- Post-race recovery involves replenishing ATP-PCr stores (50% within 30 seconds), removing accumulated lactate through aerobic metabolism, and restoring muscle pH levels.
Show Worked Solution
Sample Answer
First 2-3 seconds:
- The ATP-PCr system provides immediate energy through rapid breakdown of stored phosphocreatine, enabling explosive acceleration from starting blocks without oxygen requirement.
Seconds 3-15:
- ATP-PCr system remains dominant but begins depleting, with the runner achieving peak velocity as this system provides the highest rate of ATP production for maximum power output.
Seconds 15-30:
- Glycolytic system becomes predominant as ATP-PCr stores deplete, breaking down muscle glycogen to produce ATP anaerobically, resulting in rapid lactic acid formation.
Seconds 30-45:
- Continued dominance of glycolytic system with increasing aerobic contribution as oxygen becomes more available, though anaerobic glycolysis still provides majority of energy.
Final 15 seconds:
- All three systems operate simultaneously with glycolytic system still dominant, but accumulating lactic acid begins interfering with muscle contraction, causing performance decline.
System integration:
- The transition between systems is gradual rather than distinct, with optimal 400 metre performance requiring efficient switching between energy pathways and the ability to tolerate high lactate levels.
Recovery phase:
- Post-race recovery involves replenishing ATP-PCr stores (50% within 30 seconds), removing accumulated lactate through aerobic metabolism, and restoring muscle pH levels.