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.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
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.
Model answer (4 marks)
1. Repeat the experiment at least three times and calculate a mean heart rate.
2. Keep the duration of exercise constant (e.g. always 2 minutes of jumping jacks).
3. Ensure the independent variable (exercise intensity) is changed while all other variables are kept constant to make the test fair.
4. Allow sufficient rest between repeats so the resting heart rate returns to baseline before each trial.
2. Keep the duration of exercise constant (e.g. always 2 minutes of jumping jacks).
3. Ensure the independent variable (exercise intensity) is changed while all other variables are kept constant to make the test fair.
4. Allow sufficient rest between repeats so the resting heart rate returns to baseline before each trial.
Examiner tips
- Use bullet points or numbering to show each point clearly.
- Mention the mean calculation to demonstrate understanding of data handling.
- Show that you recognise the need for a controlled variable and rest period.
Common mistakes
- Not specifying how many repeats or failing to calculate a mean.
- Choosing a variable that is not actually controlled, e.g. different exercise types.
- Ignoring the need for a rest period, leading to inaccurate resting rates.
Mark scheme (4 marks)
- Repeat the experiment (multiple times / at least three repeats) and calculate a mean heart rate
- Identify a suitable controlled variable — e.g. duration of exercise / type of exercise / same person performing the exercise / same time of day
- Ensure the independent variable (exercise intensity / duration) is changed whilst keeping all other variables constant, to make the investigation a fair test
- Allow sufficient rest/recovery time between repeats so that the resting heart rate returns to its baseline value before each trial
Key terms in this question
heart rate · controlled variable
Related
- All OCR GCSE Biology A: Gateway Science (J247) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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