Pulse Rate, Heart Rate and the Effects of Exercise
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
During exercise, muscles respire faster and need more oxygen and glucose. The heart rate increases to pump blood faster, delivering oxygen and glucose to muscles more quickly and removing carbon dioxide more rapidly. Pulse rate: felt where an artery passes over bone: equals heart rate.
Pulse rate is one of the most common practical investigations in IGCSE Biology. Questions ask you to explain the mechanism (why heart rate increases) and to interpret data showing heart rate before, during and after exercise, including recovery time.
Why heart rate increases during exercise
Active muscles contract more frequently, requiring more energy from aerobic respiration. This demands a greater supply of oxygen and glucose, and produces more carbon dioxide that must be removed.
The heart responds by beating faster and with greater force, increasing cardiac output (the volume of blood pumped per minute). This delivers more oxygenated blood to the muscles and removes waste products more efficiently. Breathing rate also increases to supply more oxygen to the blood at the lungs.
Measuring pulse rate
A pulse is a wave of pressure that passes along an artery wall each time the heart contracts. It can be felt where an artery runs close to the surface over a bone, such as the radial artery at the wrist or the carotid artery at the neck. Pulse rate equals heart rate because each pulse corresponds to one heartbeat.
In an investigation, measure resting pulse rate before exercise, then record pulse rate at intervals during and after exercise. The time for pulse rate to return to the resting level is the recovery time. Fitter individuals typically have lower resting pulse rates and shorter recovery times.
Interpreting exercise data
A typical graph shows pulse rate rising sharply at the start of exercise, reaching a plateau during sustained exercise, and falling back toward resting rate after exercise stops. If pulse rate does not return to resting level, there may be an oxygen debt from anaerobic respiration during intense exercise.
When comparing data from two individuals, look at three things: resting rate (lower suggests greater cardiovascular fitness), maximum rate during exercise, and recovery time (shorter suggests the cardiovascular system returns to equilibrium faster).
Try a focused question (3 marks)
A student measures her pulse rate before, during and after 5 minutes of running. Her resting rate is 72 beats per minute, it rises to 140 during running, and returns to 72 after 4 minutes of rest. Explain why pulse rate increases during exercise.
Show the answer and marking guidance
Muscles are contracting more during exercise and respiring at a faster rate.
They need more oxygen and glucose delivered to them by the blood.
The heart beats faster to increase the rate of blood flow, delivering these substances more quickly and removing carbon dioxide.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Saying the heart beats faster to get more air: the heart pumps blood, not air.
Confusing pulse rate with breathing rate.
Not mentioning the need to remove carbon dioxide as well as deliver oxygen.
Forgetting that recovery time is a measure of fitness in data interpretation.
Practical connection
Investigating the Effect of Exercise on Heart Rate
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.