Physical activity and breathingSpec B11.1.2
In short
During exercise the rate and depth of breathing increase, bringing in more oxygen and removing more carbon dioxide for faster respiration.
During physical activity, your rate of breathing (the number of breaths per minute) increases. Your depth of breathing (the volume of air in each breath) also increases. Together, these bring more oxygen into the body and remove more carbon dioxide.
Investigating the effect of exercise on breathing
- Sit still and count the number of breaths taken in one minute (or count for 30 seconds and double it). This is the resting breathing rate. Repeat and calculate a mean.
- Do a set amount of exercise, such as running on the spot for 2 minutes.
- Immediately count the breaths in one minute.
- Record the rate every minute until it returns to the resting value. To measure depth, use a spirometer to find the volume of each breath, or measure chest expansion with a tape measure around the chest.
- Repeat with different intensities of exercise, allowing full recovery between each.
| Activity | Breathing rate / breaths per minute |
|---|---|
| At rest | 16 |
| After walking | 22 |
| After running | 34 |
The independent variable is the type or amount of exercise. The dependent variable is the breathing rate. Control the time for each exercise and the time of counting, use the same person, and repeat to find a mean.
Percentage change in breathing rate
A student breathes 16 times per minute at rest and 34 times per minute after running. Calculate the percentage increase.
- Increase = 34 − 16 = 18 breaths per minute
- Percentage increase = 18 ÷ 16 × 100
Answer: 112.5% (about 113%)
Quick check
Name the tubes that carry air into each lung.
Show answer
Bronchi.
Supplement State the four features of a gas exchange surface in humans.
Show answer
Large surface area, thin surface, good blood supply and good ventilation with air.
Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026