Pearson International A Level Biology Core Practical 17: Investigate exercise effects using spirometer traces

This core practical is part of Pearson's practical-learning programme. The method below is one defensible implementation, not a confidential instruction sheet. Centres may adapt equipment while preserving the scientific purpose, controls, measurements and safety requirements.

Aim and scientific principle

Interpret supplied spirometer traces to compare breathing rate, tidal volume, respiratory minute ventilation and oxygen consumption before and after exercise.

Separate values read directly from the trace from quantities calculated from them. Breathing frequency and tidal volume are measured from calibrated axes; respiratory minute ventilation is their product. Baseline slope supports an oxygen-consumption calculation only when the trace convention and apparatus conditions justify that interpretation.

Apparatus and setup

Use the supplied spirometer trace, its time and volume calibration, a ruler and a calculator. Mark the rest, exercise and recovery intervals before measuring. This core practical requires interpretation of trace data; Pearson's teacher guide does not require students to collect data with a spirometer.

Before taking measurements, verify the axis units, direction of volume change and whether the printed or digital scale has been resized. Record the reading resolution used and do not report more precision than the trace supports.

Method

1. Read the time and volume scale and identify comparable stable intervals for rest, exercise and recovery.
2. Measure tidal volume from representative peak-to-trough differences and breathing frequency from several complete cycles.
3. Calculate respiratory minute ventilation as tidal volume multiplied by breathing frequency, with consistent units.
4. Estimate oxygen consumption only when the trace and its baseline information support that calculation, then state the assumptions and any drift limitation.

Plan the calculation before selecting a trace interval. This makes the required cycle count, time span, volume difference and unit conversion explicit and prevents a visually convenient segment from replacing a consistent selection rule.

Variables and controls

• Independent variable: rest or exercise condition and recovery time.
• Dependent variable: trace-derived breathing frequency, tidal volume, respiratory minute ventilation or oxygen consumption.
• Important controls: trace calibration, interval length, cycle-selection rule, exercise intensity and recovery timing represented in the supplied data.