Describe what happens in the muscles during vigorous exercise when the body cannot supply enough oxygen, and explain why a person continues to breathe heavily for several minutes after the exercise stops.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
During vigorous exercise the muscles use anaerobic respiration because oxygen supply is insufficient. This produces lactic acid, which builds up in the muscle tissue. After exercise stops the body still needs oxygen to remove or react with the accumulated lactic acid. The extra oxygen required to clear this excess is known as the oxygen debt.
Examiner tips
- Use the term "anaerobic respiration" and "lactic acid" – these are key phrases. Explain the oxygen debt as the reason for heavy breathing after exercise. Keep the answer short and to the point – 4 marks only.
- common_mistakes
- :
- Forgetting to mention lactic acid or calling it "lactate" incorrectly. Using vague phrases like "the body needs more oxygen" without linking it to the oxygen debt. Including unnecessary details such as the exact chemical equation of glycolysis.
Mark scheme (4 marks)
- Anaerobic respiration occurs in the muscles during vigorous exercise
- Lactic acid is produced / builds up in the muscles
- After exercise, extra oxygen is needed to remove / react with the accumulated lactic acid
- This extra oxygen required is called the oxygen debt
Related
- Revision notes: Respiration →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Respiration questions
- Explain why a yeast cell producing ethanol is still described as carrying out ce…
- Explain why the body continues to breathe faster and deeper for several minutes …
- Explain why aerobic respiration is described as an exothermic reaction and state…
- Explain how lactic acid is produced during vigorous exercise and describe what h…