Place the spirometer mouthpiece in the test subjects mouth and clip their nose so all air goes through the mouth.
Get the person on the treadmill and slowly increase speed until it reaches 4m/s. Time how long it takes for the person running to feel fatigued and unable to carry on. They should then lift off the treadmill by pushing up on the sides and the treadmill should be slowed.
Repeat at intervals of 0.5m/s up to 8m/s.
The spirometer reading can give an indication of the breathing rate and volume during the test.
The runner will need adequate time for recovery between tests.
The runner will also need to be provided with an glucose drink prior to the experiment to ensure that blood sugar levels do not affect the onset of fatigue.