11.1.3B6. Respiration and Gas Exchange
Investigating the Effects of Physical Activity on Breathing — Combined Science 0653 - Biology Revision Notes & Topical Questions
5 min read 6 parts Lesson 7 of 8 Unit quiz
Section 1 of 6Idea behind the investigation
What changes during exercise
- What changes during exercise Exercise increases both the frequency of breathing (breaths per minute) and its depth (the volume of air moved with each breath).
- Both can be measured with simple equipment in a classroom.
Variables
- Variables Independent variable: the activity, resting compared with exercising.
- Dependent variablesnumber of breaths per minute and the average chest expansion.
- Control variablesthe same person, same type and duration of exercise, same room temperature and the same method of measuring.
Section 2 of 6Method
1
While the volunteer sits quietly at rest, count the number of breaths taken in one minute.
2
Place a tape measure around the chest and record the chest circumference when fully breathed in and fully breathed out over five breaths. Work out the average chest expansion.
3
The volunteer then exercises for a fixed time of at least three minutes, for example star jumps or jogging on the spot.
4
Immediately after stopping, count the breaths in one minute again.
5
Measure the average chest expansion over five breaths once more.
6
Repeat the investigation with other volunteers or on other days and calculate mean values.
Section 3 of 6Results and processing
| Measurement | At rest | After exercise |
|---|---|---|
| Breaths per minute | Lower, typically 12 to 18 | Higher |
| Average chest expansion (cm) | Smaller | Larger |
| Conclusion | Normal ventilation | Faster and deeper breathing |
Section 4 of 6Making the results reliable
Good practice
Repeat readings
- Repeat readings Take several measurements and calculate a mean to reduce the effect of random error.
Same conditions
- Same conditions Use the same exercise for the same time so that the only change is activity level.
Safety
- Safety Ensure volunteers are fit and healthy, have space to move safely, and can stop at once if they feel unwell.
Recovery time
- Recovery time Allow breathing to return to the resting rate before any repeat so that the starting point is the same each time.
Section 5 of 6Key terms
| Term | Meaning |
|---|---|
| Breathing rate | The number of breaths taken in one minute. |
| Depth of breathing | The volume of air moved in and out in a single breath. |
| Chest expansion | The increase in chest circumference when breathing in. |
| Independent variable | The factor that the investigator deliberately changes. |
| Dependent variable | The factor that is measured to see the effect of the change. |
Section 6 of 6Exam technique
1
Measuring breathing after waiting several minutes — the rate falls quickly once exercise stops, so count immediately.
2
Changing the type or length of exercise between volunteers, which makes the comparison unfair.
3
Counting only one breath for chest expansion instead of the average of several.
4
Confusing breathing rate (breaths per minute) with depth of breathing (volume per breath).
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