Reading a spirometer trace
Tidal volume is one normal breath: the top of the breath minus the bottom. Count the breaths in a known time for the breathing rate, then multiply: minute ventilation = tidal volume × breaths per minute. The deepest breath in to the fullest breath out is the vital capacity. In exercise the breaths get deeper and faster, eating into both reserve volumes. With soda lime in the spirometer the whole trace drifts down by the oxygen used, so its fall in one minute is the oxygen uptake.
Heart rate graphs show the resting rate, a small anticipatory rise before exercise, a steady state (or a climb to the maximum in hard work) and a recovery that is fast at first and then slow. Oxygen uptake curves lag behind the oxygen required: that gap is the oxygen deficit, and the extra oxygen taken in afterwards is EPOC. Graph readings are right within half a small square.
Example: rest and exercise
In set SP5522 (A-level PE), the exercise breaths run from 2.2 to 4.2 litres, so the tidal volume is 4.2 − 2.2 = 2.0 litres. There are 10 breaths in the 20 seconds of exercise, which is 30 breaths per minute, so minute ventilation is 2.0 × 30 = 60 litres per minute. Open set SP5522
Two ways to set a training zone
| Method | Target heart rate | Where it is used |
|---|---|---|
| % of maximum | % × (220 − age) | AQA GCSE PE: aerobic 60–80%, anaerobic 80–90% |
| Heart rate reserve (Karvonen) | resting + % × (maximum − resting) | US activity guidelines: moderate 40–59%, vigorous 60–84% of reserve (stated for aerobic capacity reserve; the questions here apply it to heart rate reserve) |
OCR A-level PE asks for target heart rates without naming a method, and the AQA A-level PE specification does not list training zones, so the A-level preset starts on Karvonen and you can switch under Question types and zones. The US preset uses heart rate reserve only. Every question says which method to use. This is study practice, not training or medical advice: 220 − age is only an estimate of maximum heart rate.
Questions
How do you calculate tidal volume from a spirometer trace?
Take one normal breath. Read the top and the bottom of the breath against the grid and subtract: top minus bottom is the tidal volume. At rest it is usually about half a litre. During exercise each breath goes higher and lower, so the tidal volume grows.
How do you work out breathing rate and minute ventilation?
Count the breaths in a known time and scale to one minute: 10 breaths in 20 seconds is 30 breaths per minute. Minute ventilation is tidal volume times breathing rate, so 2.0 litres × 30 = 60 litres per minute.
How do you find oxygen uptake from a spirometer trace?
With soda lime in the spirometer, the carbon dioxide breathed out is absorbed, so the air in the spirometer falls by the oxygen used. Draw a line through the peaks, read how far it falls in one minute, and that is the oxygen uptake per minute.
Why does the trace go down when breathing in?
It depends on what is plotted. A trace of the air in the spirometer falls when you breathe in; a lung volume diagram rises. The biology questions here plot the spirometer and the PE ones the lungs, and each says so. The volumes you read are the same either way.
How do you work out training zones in GCSE PE?
AQA GCSE PE uses maximum heart rate = 220 − age. The aerobic training zone is 60% to 80% of that, and the anaerobic zone 80% to 90%. For a 16-year-old the maximum is 204 bpm, so the aerobic zone is 122.4 to 163.2 bpm, about 122 to 163.
What is the Karvonen formula?
It sets a target from the heart rate reserve, the gap between maximum and resting heart rate: target = resting + % × (maximum − resting). With a maximum of 204 and a resting rate of 60, 60% is 60 + 0.6 × 144 = 146.4 bpm, higher than 60% of the maximum.
What units is cardiac output in?
Cardiac output is stroke volume times heart rate. Stroke volume is in ml (cm³ in biology) and heart rate in beats per minute, so the product is ml per minute; divide by 1000 for litres per minute (dm³ min⁻¹). 70 ml × 72 = 5040 ml per minute, about 5 litres per minute.
Can I give my class the same questions?
Yes. Share with class copies a link with the set code, and everyone who opens it gets the same graphs and numbers. To stop copying, print a class set: each copy asks the same kinds of question in the same order with different numbers, and each has its own key.
Sources, read October 27, 2026: AQA GCSE PE 8582 specification (Q = SV × HR, heart rate graphs, spirometer volumes, 220 − age and the training zones); AQA A-level PE 7582 specification (lung volumes, minute ventilation, oxygen deficit, EPOC); OCR A Level PE H555 specification (resting values and calculations, fast and slow EPOC, target heart rates); AQA Biology 7401/7402 specification (PVR = tidal volume × breathing rate, CO = stroke volume × heart rate); OCR Biology A specification (vital capacity, tidal volume, breathing rate and oxygen uptake from a spirometer); Physical Activity Guidelines for Americans, 2nd edition (relative intensity as a % of maximal heart rate, heart rate reserve or aerobic capacity reserve; moderate 40–59% and vigorous 60–84% of aerobic capacity reserve); Karvonen, Kentala and Mustala, Annales Medicinae Experimentalis et Biologiae Fenniae, 1957 (the heart rate reserve method).