Plan a controlled heart-rate investigation
Compare rest and activity using an appropriate supervised method or supplied records.
Section 9.2 · Heart
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall pulse rate and conversion to beats per minute.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the dependent variable in this comparison?
What you will learn
- Choose the comparison and the measurements
- Control other influences and repeat the observation
Choose the comparison and the measurements
An investigation can compare heart rate before and after a stated period of physical activity. Record a resting baseline after a consistent rest period, then measure using the same method and count duration after a standardised activity. Write the activity’s duration and intensity in the plan so the comparison is reproducible.
For a school activity, participation and the chosen movement should be appropriate and teacher-supervised. Supplied records provide an alternative without requiring a learner to exercise. Do not use this lesson to push maximal effort or diagnose fitness. Written planning and data interpretation do not demonstrate that practical work has been performed.
Control other influences and repeat the observation
Keep count duration, measurement method, starting posture, activity duration and the delay before measurement consistent. To compare activity levels, change only the intended activity condition as far as practical. A delayed count may miss the immediate peak because recovery starts as soon as activity ends.
Repeat comparable observations with suitable recovery between them, and retain all readings. Calculate a mean rather than choosing only the most convenient result. Comparing two different people confounds the activity effect with individual differences unless the design accounts for each person’s own baseline.
Pause and explain
Which change improves a rest/activity comparison?
Worked example
Improve a plan that uses a 15-second rest count and a 60-second count two minutes after activity.
Show the worked solution
- Convert counts to the same rate unit and use a consistent sampling duration.
- Standardise the measurement delay; two minutes may reflect recovery rather than the immediate activity response.
Answer Use the same method and count duration, report beats per minute, and measure after a specified consistent delay with suitable supervised repeats.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State an independent condition, dependent variable and two controls for a rest/activity comparison.
Give me a hint
Separate the activity condition from the measured rate.
Compare my reasoning
- Condition: rest versus the defined activity.
- Response: heart rate; control count duration and measurement delay.
Rest versus stated activity; heart rate in beats per minute; consistent count duration and post-activity delay.
Look for these in your work
- Separate condition and response
- Give two relevant controls
Why should repeated trials use an appropriate recovery period rather than beginning the next trial immediately?
Give me a hint
The previous activity can alter the next baseline.
Compare my reasoning
- Residual elevated rate would confound the starting condition.
- Comparable recovered baselines improve repeatability.
Allow appropriate supervised recovery so the previous trial does not determine the next starting heart rate.
Look for these in your work
- Identify the carry-over effect
- Connect recovery with a comparable baseline
Two learners have different resting rates, then perform different activities. Why can their final rates alone not establish which activity caused the larger increase?
Give me a hint
You need baselines and a comparable activity design.
Compare my reasoning
- People differ before activity.
- Calculate each change from baseline and standardise the planned conditions.
Different final rates combine baseline differences and activity effects; compare each change from baseline under controlled conditions.
Look for these in your work
- Identify the confounding factor
- Propose a baseline-based comparison
Common mistakes
- Comparing raw counts from unequal times.
- Treating written planning as completed practical evidence.
What can you explain now?
Which change improves a rest/activity comparison?
Compare with the explanation
Use the same count duration and standardised timing
This makes observations comparable.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Write a measurement plan another learner could follow, then state what the plan cannot certify.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.