Investigating the Effect of Exercise on Heart Rate
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
What this skill means
Exercise increases heart rate because muscles need more oxygen and glucose for increased aerobic respiration. Heart rate rises quickly during exercise and gradually returns to resting rate during recovery: fitter individuals recover faster.
This practical links the circulatory system with respiration and is a favourite Paper 5/6 question. You need to know how to measure pulse rate accurately, design a fair test, and explain the biology behind the results.
The Standard Method
1. Measure resting heart rate by counting the pulse at the wrist (radial artery) for one full minute while sitting still. Repeat three times and calculate a mean.
2. The subject performs a set exercise (e.g. Stepping up and down on a bench 30 times, or jogging on the spot for 2 minutes).
3. Immediately after stopping, measure heart rate every minute for 5–10 minutes until it returns to the resting rate.
4. Plot heart rate (y-axis) against time after exercise (x-axis) to show the recovery curve.
Explanation of Results
During exercise:
Muscles contract more frequently and require more energy
Energy is released by aerobic respiration, which needs more oxygen and glucose
The heart beats faster to pump more blood to the muscles, delivering oxygen and glucose more quickly
Faster blood flow also removes carbon dioxide (a waste product of respiration) more quickly
After exercise:
Oxygen demand decreases as muscles stop contracting intensely
Heart rate gradually decreases back to the resting rate
If anaerobic respiration occurred, the body must also repay the oxygen debt by breaking down lactic acid
Controlling Variables
For a fair comparison between individuals or conditions:
Same type and duration of exercise
Same resting period before starting
Measurements at the same time intervals
Subject should not eat, drink caffeine, or exercise beforehand (these can affect resting heart rate)
For comparing fitness levels, measure the recovery time: the time it takes for heart rate to return to the resting rate. A fitter person has a shorter recovery time because their cardiovascular system is more efficient at delivering oxygen and removing waste.
Use this before submitting your answer
A complete answer is specific enough for another person to repeat or assess.
✓Measure resting heart rate three times and calculate a mean.
✓Use a standardised exercise (same type, same duration or number of repetitions).
✓Measure heart rate immediately after exercise and at regular intervals (e.g. Every minute).
✓Continue until heart rate returns to resting level.
✓Record all data in a clear table with time and heart rate columns.
✓Plot a recovery curve graph (heart rate vs time after exercise).
✓Identify the recovery time from the graph.
Try the skill in a question (3 marks)
Explain why heart rate increases during vigorous exercise. [3]
Show the answer and marking guidance
During exercise, muscles need more energy for increased contraction
More aerobic respiration occurs, which requires more oxygen and glucose
The heart beats faster to pump blood more quickly to the muscles, delivering more oxygen and glucose and removing carbon dioxide faster
Original practice content written for this site. It is not an official Cambridge question.