ZIMFundi
Sign inJoin free

Topic 1 of 6 · Form 5

Exercise physiology and energy systems

ATP is the only immediate source of energy for muscle contraction; it is resynthesised by three systems:

Notes for this topic 1 file, in order

Create a free account to download PDFs.

  1. PDFExercise physiology and energy systems – Physical Education, Sport and Mass Displays notes (ZIMSEC A Level)47.7 KB

Energy systems

ATP is the only immediate source of energy for muscle contraction; it is resynthesised by three systems:

  • ATP–PC (phosphocreatine) system: anaerobic, very fast, lasts about 8–10 seconds (100 m sprint, shot put).
  • Anaerobic glycolytic (lactic acid) system: about 10 seconds to 2–3 minutes (400 m); produces lactate and fatigue.
  • Aerobic system: glycolysis, Krebs cycle and electron transport chain; long duration (marathon); uses carbohydrates and fats.

The energy continuum shows how systems overlap depending on intensity and duration.

Cardiovascular and respiratory responses

  • Cardiac output Q = stroke volume × heart rate.
  • VO₂ max: maximum oxygen uptake – a measure of aerobic fitness, improved by endurance training.
  • Training effects: lower resting heart rate, larger stroke volume (cardiac hypertrophy), more capillaries and mitochondria.

Worked example: An athlete has a stroke volume of 90 ml and a heart rate of 150 bpm during exercise. Find the cardiac output.

Q = 0.090 L × 150 = 13.5 L/min

Recovery

Excess post-exercise oxygen consumption (EPOC): fast component (restores ATP–PC) and slow component (removes lactate, restores temperature and glycogen). Active recovery speeds lactate removal.

Altitude and heat

Training at altitude increases red blood cell production; heat increases dehydration risk – relevant in Zimbabwe's hot season.

Exam tip: Link each energy system to a specific sport and its duration and intensity.

Check yourself

  1. Which energy system dominates a 100 m sprint?
  2. Define VO₂ max.
  3. What is EPOC?
Show answers
  1. The ATP–PC (phosphocreatine) system.
  2. The maximum volume of oxygen the body can take in and use per minute.
  3. Excess post-exercise oxygen consumption – extra oxygen used after exercise to restore the body to its resting state.
Next topicBiomechanics

Questions about this topic (0)

No questions about this topic yet.