How do the three energy systems resynthesise ATP for different sporting intensities?
ATP and its resynthesis by the ATP-PC, glycolytic and aerobic systems, their fuels, sites, by-products, ATP yield and duration, and the energy continuum across sporting activities.
A focused answer to OCR A-Level PE on energy systems: ATP as the energy currency, the three systems that resynthesise it (ATP-PC, anaerobic glycolytic and aerobic), each with its fuel, site, by-products, ATP yield and duration, and how the energy continuum and OBLA explain the system used in different sports.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
OCR wants you to explain ATP as the energy currency, describe how each of the three energy systems resynthesises ATP (its fuel, site, by-products, ATP yield and duration), and use the energy continuum and OBLA to explain which system predominates in a given sport.
ATP, the energy currency
The ATP-PC (alactic) system
The enzyme creatine kinase breaks down PC, and the energy released rebonds ADP and phosphate into ATP. PC is restored within a few minutes of rest, which is why interval training with recovery suits speed events.
The anaerobic glycolytic (lactic) system
The aerobic system
The energy continuum
No system works alone. The energy continuum describes how the three systems all contribute at once, with the dominant system set by the intensity and duration of the activity. Intermittent games such as football, hockey and rugby use all three: aerobic for low-intensity jogging, ATP-PC for short explosive bursts, and the glycolytic system for sustained high-intensity efforts. The thresholds (the energy system thresholds) mark where one system gives way to the next as intensity rises.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksA 400 m runner completes the race in 48 seconds. Identify the predominant energy system, name its fuel and main by-product, and explain why fatigue occurs late in the race.Show worked answer →
A Component 01 application question. One mark each for the system, the fuel, the by-product and the fatigue explanation.
Award marks for: the predominant system is the anaerobic glycolytic (lactic) system, because the race is high intensity and lasts about 10 seconds to 3 minutes. Its fuel is glucose or glycogen, and its main by-product is lactate (lactic acid) and hydrogen ions. Fatigue occurs late because the accumulation of hydrogen ions lowers the pH of the muscle (the runner reaches OBLA), inhibiting the enzymes of glycolysis and muscle contraction.
Markers reward linking fatigue specifically to hydrogen ion accumulation and falling pH, not just "lactic acid".
OCR 20218 marksAnalyse how the three energy systems contribute across a game of football, using the idea of the energy continuum.Show worked answer →
A Component 01 extended-response (levels of response) question. Markers reward accurate system characteristics (AO1), application to the changing intensity of football (AO2) and a reasoned account of the continuum (AO3).
Award credit for: football is intermittent, so all three systems contribute and the dominant one shifts with intensity (the energy continuum). Standing and jogging at low intensity is fuelled aerobically, using glucose and fats with oxygen to yield 36 to 38 ATP per glucose, with carbon dioxide and water as harmless by-products. A short explosive sprint or shot of up to about 8 to 10 seconds uses the ATP-PC system, fuelled by phosphocreatine, which gives one ATP per molecule very rapidly with no fatiguing by-product. Repeated high-intensity efforts of up to 2 to 3 minutes draw on the anaerobic glycolytic system, yielding 2 ATP per glucose but producing lactate and hydrogen ions that cause fatigue. During recovery jogs the aerobic system replenishes phosphocreatine and removes lactate.
A top answer ties the dominant system to specific phases of play and judges that no single system works alone, which is the meaning of the continuum.
Related dot points
- The cardiac cycle, the regulation of heart rate, cardiac output and the cardiovascular drift, venous return mechanisms, and the redistribution of blood flow during exercise.
A focused answer to OCR A-Level PE on the cardiovascular system: the cardiac cycle and conduction, neural and hormonal control of heart rate, cardiac output and its calculation, the venous return mechanisms, the Starling effect, and the redistribution of blood flow (the vascular shunt) during exercise.
- The mechanics of breathing, lung volumes and minute ventilation, gaseous exchange at the alveoli and muscles by diffusion, and the regulation of breathing during exercise.
A focused answer to OCR A-Level PE on the respiratory system: the mechanics of inspiration and expiration, tidal volume and minute ventilation, gaseous exchange at the alveoli and muscle by diffusion down partial-pressure gradients, the oxyhaemoglobin dissociation curve and the Bohr shift, and the neural and chemical control of breathing.
- Joint types and movements, the antagonistic muscle action that produces them, muscle contraction types, and the three muscle fibre types with their roles in sport.
A focused answer to OCR A-Level PE on the skeletal and muscular systems: the synovial joints and their movements, antagonistic muscle action with agonist, antagonist and fixator, the three contraction types, and the structure and roles of the three muscle fibre types.
- Excess post-exercise oxygen consumption and its fast and slow components, the replenishment of phosphocreatine and the removal of lactate, and recovery strategies that speed return to readiness.
A focused answer to OCR A-Level PE on recovery and EPOC: the alactacid (fast) and lactacid (slow) components of excess post-exercise oxygen consumption, the resynthesis of phosphocreatine, the fate and removal of lactate, oxygen myoglobin restoration, and the recovery strategies that return a performer to readiness.
- The principles of training, the main training methods for aerobic, anaerobic, strength and flexibility goals, and the long-term cardiovascular, respiratory and muscular adaptations they cause.
A focused answer to OCR A-Level PE on training methods and adaptations: the principles of training (specificity, overload, progression, reversibility), the methods for aerobic, anaerobic, strength and flexibility goals including HIIT and PNF, and the long-term cardiovascular, respiratory and muscular adaptations and their performance benefits.
Sources & how we know this
- OCR A Level Physical Education (H555) specification — OCR (2016)