Energy Systems and Their Interplay in Physical Activity

Chapter 6: The Interplay of Energy Systems

Key Knowledge

• Understanding oxygen uptake at rest, during exercise, and recovery:

  • Oxygen deficit: Shortfall between oxygen supply and demand at the onset of exercise.

  • Steady state: When oxygen supply meets demand, plateau in heart rate and ventilation.

  • EPOC (Excess Post-exercise Oxygen Consumption): Oxygen consumed during recovery above resting levels.

Key Skills

• Perform and analyse practical activities exploring the relationship between energy systems.

• Use appropriate terminology to describe the interplay of the 3 energy systems.

• Explain mechanisms of muscular fatigue and influencing factors during exercise.

Assessment Outcomes

1. Outcome 1: Analyse primary data from physical participation to refine skills using biomechanical and acquisition principles (45 marks).

2. Outcome 2: Use practical data to analyse body and energy systems, fatigue factors, and recovery strategies (45 marks).

   • Total: 90 marks

   • Coursework contributes 20% to final assessment.

Energy Systems Overview

• Anaerobic Energy Systems:

  • ATP-PC System: Uses phosphocreatine, quick energy for max efforts, lasts about 10 seconds.

  • Anaerobic Glycolysis: Breaks down glycogen without oxygen, produces lactate, duration of 30-40 seconds.

• Aerobic Energy System: Requires oxygen, slower but more sustainable energy from carbs and fats over longer durations (greater than 2 minutes).

Characteristics of Energy Systems

• ATP-PC System:

  • Rate: Fastest (110 ATP).

  • Yield: Low (0.7-1 ATP).

  • Duration: Up to 10 seconds.

  • Fuel: Phosphocreatine.

• Anaerobic Glycolysis:

  • Rate: Fast (80 ATP).

  • Yield: Moderate (2-3 ATP).

  • Duration: 30-40 seconds.

  • Fuel: Glucose.

• Aerobic System:

  • Rate: Moderate (60 ATP).

  • Yield: High (36-38 ATP with glucose).

  • Duration: Dominant after 2 minutes.

  • Fuel: Carbohydrates and fats.

Fuel Sources and Partitioning

• Carbohydrates (CHO):

  • Preferred source during exercise, breaking down requires less oxygen.

  • Stored as glycogen in the muscles and liver.

• Fats:

  • Main source at rest; slower to oxidize than carbohydrates.

• Proteins:

  • Used for recovery, growth, not preferred for energy during exercise.

Factors Influencing Energy System Use

• Intensity: Higher intensity relies more on anaerobic systems.

• Duration: Prolonged exercise shifts reliance to the aerobic system.

• Oxygen availability: Needed for the aerobic system, affects performance during high-intensity efforts.

• Fuel availability: Depleting glycogen affects performance and energy system efficiency.

Recovery and EPOC

• Recovery strategies include:

  • Passive recovery: Optimal for phosphocreatine (PC) replenishment.

  • Active recovery: 35-65% VO2max, helps in lactate removal and metabolic by-product clearance.

• EPOC Role: Oxygen debt repayment post-exercise, aids in recovery processes.

Summary of Energy System Contribution

• Different events engage energy systems variably:

  • Short sprints favor ATP-PC.

  • Mid-distance (e.g., 400m) garners anaerobic contributions.

  • Longer endurance events (e.g., marathons) rely on aerobic systems.

• Example: An Ironman (3.8KM swim, 180KM bike, 42.2 KM run) engages all energy systems with shifting contributions based on exercise duration and intensity.

Practice Questions and Applications

• Familiarize with application questions related to energy systems and their interplay during various sports activities. Pay attention to specific terminology and mark allocation when preparing answers.

PC RESTORATION RATES

30 60 90 120 150 180 10

70 75 93 95 97 98 100

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