# A student takes part in a sprint race. During the race, the student's muscles respire anaerobically. Explain why anaerobic respiration occurs during a sprint and describe what happens in the student's body after the race to return conditions to normal.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 7 Run for your Life · Explain · 5 marks

> During intense exercise such as sprinting, the muscles demand energy at a rate that cannot be sustained by aerobic respiration alone. After the race, the student continues to breathe rapidly and deeply for several minutes.

## Mark scheme (5 marks)

1. During a sprint, the muscles require energy faster than oxygen can be delivered / aerobic respiration cannot supply ATP fast enough
2. Anaerobic respiration produces lactic acid in the muscles
3. After the race, the student continues to breathe rapidly / takes in extra oxygen (excess post-exercise oxygen consumption / repays the oxygen debt)
4. The extra oxygen is used to oxidise / break down lactic acid (in the liver)
5. Glycogen stores in the muscles / liver that were broken down during exercise are replenished (as part of recovery)

## Key terms

- [anaerobic respiration](https://www.gradenine.co.uk/glossary/anaerobic-respiration)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-takes-part-in-a-5f65d6b1) · Published by Druglandscape Ltd.