# A student is investigating how exercise affects heart rate. They plan to measure their resting heart rate, perform jumping jacks for two minutes, and then measure their heart rate again. Describe how the student should make this investigation reliable and valid, and identify one controlled variable they should use.

> OCR GCSE Biology A: Gateway Science (J247) — B7 Practical skills · Describe · 4 marks

> A student wants to investigate the effect of exercise intensity on heart rate. They decide to compare their heart rate before and after a period of exercise.

## Mark scheme (4 marks)

1. Repeat the experiment (multiple times / at least three repeats) and calculate a mean heart rate
2. Identify a suitable controlled variable — e.g. duration of exercise / type of exercise / same person performing the exercise / same time of day
3. Ensure the independent variable (exercise intensity / duration) is changed whilst keeping all other variables constant, to make the investigation a fair test
4. Allow sufficient rest/recovery time between repeats so that the resting heart rate returns to its baseline value before each trial

## Key terms

- [heart rate](https://www.gradenine.co.uk/glossary/heart-rate)
- [controlled variable](https://www.gradenine.co.uk/glossary/controlled-variable)

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-is-investigating-how-exercise-ae3752fd) · Published by Druglandscape Ltd.