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Anaerobic respiratory system

The respiratory system supplies energy very quickly for sports such as vaulting in gymnastics or throwing a javelin where the activity only lasts a few seconds.

An athlete about to throw a javelin
Athletes showing signs of fatigue and pain towards the end of a 400 m race
Figure caption,
Athletes showing signs of fatigue and pain towards the end of a 400 m race

This system breaks down glucose into lactic acid. Glucose is derived from carbohydrates. It produces energy very quickly.

Glucose 鈫 energy + lactic acid

The lactic acid energy system produces the majority of the energy for moderate to high intensity activities such as running 400 metres. However, lactic acid is a fatiguing by-product of this energy pathway and causes pain and discomfort in the working muscles. It is for this reason that the winner of a 400 m race is typically the athlete who slows down the least.

Oxygen debt

Christine Ohuruogu exhausted after completing the women's 400 m race
Figure caption,
Christine Ohuruogu exhausted after completing the women's 400 m race

It is the lack of oxygen and the build-up of lactic acid that causes fatigue.

The anaerobic systems require oxygen to restore them which is called an oxygen debt.

After taking part in exercise, a person continues to breathe more deeply and rapidly than when at rest to take in additional oxygen to repay this oxygen debt.

The oxygen is then used to:

  • break down lactic acid to carbon dioxide and water
  • replenish the creatine phosphate stores