Applying Energy Systems to Sport

This final lesson in the topic brings together everything you have learned about aerobic and anaerobic exercise, training thresholds, short-term and long-term effects of exercise, red blood cells, lactic acid, recovery, and vascular shunting. The Edexcel GCSE PE specification (1PE0) requires you not only to know these concepts individually, but also to apply them to real sporting scenarios. This lesson focuses on integration — linking multiple concepts together in the way that exam questions demand.

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Why Integration Matters

In the Edexcel GCSE PE exam, the highest-mark questions (typically 6 and 9 markers) require you to draw on knowledge from multiple areas of the specification. You will not simply be asked "Define aerobic exercise" (1 mark). Instead, you will be asked questions such as:

• "Analyse the energy systems used by a games player during a match and explain the effects on the body." (9 marks)
• "Evaluate the importance of an active cool-down for a sprinter." (6 marks)
• "Explain how the body of a trained marathon runner differs from an untrained individual." (6 marks)

To answer these well, you must be able to link concepts together in a logical chain.

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Case Study 1: A Football Match (90 Minutes)

Football is an excellent example of a sport that uses both energy systems extensively.

Energy Systems in Use

Phase of Play	Intensity	Energy System	By-product
Jogging between plays	Low to moderate	Aerobic	CO₂ and water
Sprinting to chase a through ball	High / maximal	Anaerobic	Lactic acid
Walking during a stoppage	Very low	Aerobic	CO₂ and water
Jumping for a header	Explosive, very short	Anaerobic	Lactic acid
Sustained pressing of the opposition	Moderate to high	Predominantly aerobic (with anaerobic bursts)	Mix

Short-Term Effects During the Match

• Heart rate fluctuates throughout, rising sharply during sprints (anaerobic zone, above 80% MHR) and dropping during walking phases (below aerobic threshold or in the aerobic zone).
• Breathing rate and depth increase to supply more oxygen and remove CO₂.
• Body temperature rises; the player sweats heavily and experiences vasodilation to lose heat through the skin.
• During anaerobic sprints, lactic acid builds up. During lower-intensity phases, the body has an opportunity to break it down aerobically.
• Vascular shunting directs blood to the working muscles and skin, and away from the digestive system (this is why players should eat 2–3 hours before kick-off).

Long-Term Adaptations for a Footballer

A footballer who trains regularly will develop:

Adaptation	Benefit for Football
Cardiac hypertrophy and increased stroke volume	Greater cardiac output to sustain 90 minutes of running
Bradycardia	More efficient heart; recovers more quickly between sprints
Increased blood volume and red blood cells	More O₂ delivered to muscles; better aerobic endurance
Capillarisation	Faster O₂ delivery and CO₂/lactic acid removal
Increased vital capacity	More efficient breathing
Muscular hypertrophy (legs)	Greater power for sprinting, jumping, kicking
Increased bone density	Reduced fracture risk from tackles and impacts

graph TD
    A[Football Match<br>90 Minutes] --> B[Predominantly AEROBIC<br>Jogging, running, positioning]
    A --> C[Frequent ANAEROBIC Bursts<br>Sprints, tackles, shots, jumps]
    B --> D[O₂ used<br>CO₂ + H₂O produced]
    C --> E[Lactic acid produced<br>Fatigue in short bursts]
    B --> F[Long-term aerobic training<br>improves cardiovascular endurance]
    C --> G[Interval training develops<br>anaerobic fitness and recovery]
    E --> H[Active phases between sprints<br>help break down lactic acid]

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Case Study 2: A 400 m Sprint

The 400 m is one of the most demanding events in athletics because it requires near-maximal effort for approximately 45–55 seconds — long enough that lactic acid builds up severely, but too fast for the aerobic system to dominate.

Energy Systems in Use

Phase	Approx. Duration	Energy System
Start and first 100 m	0–12 seconds	Primarily anaerobic (phosphocreatine then anaerobic glycolysis)
Middle 200 m	12–40 seconds	Predominantly anaerobic with some aerobic contribution
Final 100 m	40–55 seconds	Anaerobic — severe lactic acid accumulation

What Happens to the Body

1. Heart rate reaches near-maximum (often 180–200+ bpm) — deep into the anaerobic training zone (80–90% MHR and beyond).
2. Breathing rate is elevated, but the intensity is so high that oxygen cannot be delivered fast enough.
3. Lactic acid accumulates rapidly in the legs, causing the "tie-up" — the burning, heavy-legged feeling in the final 100 m.
4. Vascular shunting directs almost all blood to the working leg muscles.
5. After the race, the athlete bends over or walks, breathing heavily — repaying the oxygen debt (EPOC).

Recovery After the 400 m

• Active cool-down (light jogging) maintains blood flow and transports lactic acid to the liver faster.
• Oxygen debt is repaid: extra O₂ breaks down lactic acid, resaturates myoglobin, and replenishes phosphocreatine.
• Heart rate and breathing rate gradually return to normal over several minutes.
• Hydration and nutrition aid recovery.

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Case Study 3: A Marathon (42.2 km)

The marathon is an almost entirely aerobic event, run at moderate intensity for over two hours.

Energy Systems in Use

Phase	Energy System	Notes
Entire race	Predominantly aerobic	Sustained moderate intensity; O₂ supply meets demand
Final sprint to the finish	Brief anaerobic burst	Short, high-intensity effort at the end

Key Physiological Factors