Effects of exercise


Independent variable: Whether the test subject is resting or exercising.
Dependent variable: Tidal volume and breathing rate.


Equipment list


  • Spirometer
  • Soda lime or carbosorb - these absorb the carbon dioxide released during the experiment
  • Disinfectant wipes
  • Oxygen cylinder
  • Human test subject
  • Kymograph
  • Nose clip


Method


A spirometer is a piece of equipment that can be used to calculate the air capacity of someone’s

lungs. To use it, it must first be calibrated as follows:

  • Empty the spirometer so no air remains in it, align the pen to the paper so it can record

results.

  • Now add a set volume of air to the spirometer, such as 1 dm3 and again let the pen mark on

the graph. From this you can use the horizontal scale to calculate how many squares on the

graph are equivalent to the volume of air just added to the spirometer.


You can now begin the main part of the experiment with the calibrated spirometer.

1. Get the test subject to sit down in front of the spirometer and get them to put a nose clip on

so they are only breathing through their mouth.

2. Insert the disinfected mouthpiece of the spirometer into the student’s mouth and allow them

to breathe normally until they’re are accustomed to breathing into the apparatus.

3. Set the kymograph to a rate of 1 mm per second and turn it on so it starts rotating.

4. After an exhalation, adjust the 2-way tap so the subject is now breathing through the

spirometer equipment instead of the normal atmosphere.

5. Record their normal, resting breathing for a minute and then ask them to breathe deeply for

one breath, then returning to normal breathing for another minute.

6. Now ask them to breathe out as deeply as they can, again returning to normal breathing

afterwards.

7. The effects of exercise can then be observed by switching the spirometer to the closed

position and asking the test subject to exercise for 2 minutes - such as running on the spot

or star jumps.

8. Then immediately reinsert the mouthpiece, turn the spirometer to the open position and

record the results for 1 minute.




A graph similar to the one above will be produced.


By using the scale calculated when calibrating the spirometer the tidal volume can be calculated.

The breathing rate can be calculated by counting the number of breaths occuring in a set volume

of time e.g. in 20 seconds.


From here, the respiratory minute ventilation can be calculate for before and after exercise using

the following formula:


Respiratory minute ventilation (dm per minute) = Tidal volume (dm ) x Breathing rate 3 3

(breaths per minute)