Energy systems: Anaerobic energy system.

The idea

The anaerobic energy system supplies ATP without oxygen. It has two parts: the ATP-PC system, which uses phosphocreatine (PC) stored in muscle to rebuild ATP very fast for a few seconds of maximal work, and the lactic acid system, which breaks down glucose to pyruvate and then lactate, releasing energy for high-intensity efforts of roughly ten seconds to about two minutes. Anaerobic means no oxygen is used, so the system works at the start of exercise and during sprints, jumps and heavy lifts. ATP is the only usable energy currency: it splits to ADP and inorganic phosphate, releasing energy for muscle contraction. Recovery uses oxygen to repay the deficit.

What earns the marks

• Anaerobic means ATP is resynthesised without oxygen.
• The anaerobic system has two components: the ATP-PC (phosphocreatine) system and the lactic acid (anaerobic glycolysis) system.
• ATP is the usable energy currency; it splits into ADP and inorganic phosphate, releasing energy for muscle contraction.
• The ATP-PC system uses stored phosphocreatine to rebuild ATP rapidly for short, maximal bursts.
• The lactic acid system breaks down glucose to pyruvate and then lactate, supplying ATP for high-intensity work lasting roughly ten seconds to about two minutes.
• Anaerobic contributions dominate at the start of exercise and during high-intensity efforts; oxygen is used afterwards to repay the oxygen deficit.

Common mistakes and how to put them right

• Thinking anaerobic means no energy is released.

  Put it right: Anaerobic means no oxygen is used, but ATP is still resynthesised and energy is released.

• Confusing the two anaerobic components.

  Put it right: The ATP-PC system uses phosphocreatine, while the lactic acid system uses glucose breakdown to lactate.

• Believing lactate is a waste product with no further role.

  Put it right: Lactate can be transported to other muscles, the heart and the liver and used or converted, and it is linked to fatigue when it accumulates.

• Assuming the anaerobic system only works at rest.

  Put it right: It dominates during short, high-intensity exercise and at the start of all exercise.

Exam tips

• Learn the two components by name and by fuel so you can match each to a sporting example.
• Use precise terms such as resynthesise, phosphocreatine, glucose, pyruvate and lactate rather than vague words like energy stuff.
• When a question gives a duration or intensity, decide which anaerobic component fits best before choosing an answer.