Respiratory system
The human respiratory system is adapted to allow air to pass in and out of the body, and for efficient gas exchange to happen. Exercise and smoking both affect the lungs and circulatory system.
Effects of exercise on breathing
During exercise there is an increase in physical activity and muscle cells respire more than they do when the body is at rest.
The heart rate increases during exercise. The rate and depth of breathing increases - this makes sure that more oxygen is absorbed into the blood, and more carbon dioxide is removed from it.
The rate of breathing can be measured by counting the number of breaths in one minute. The depth of breathing can be measured using a spirometer (a device that measures the volume of air inhaled and exhaled).
To investigate the effects of exercise on breathing, record the rate of breathing for a few minutes when the person is at rest. After they do some exercise, record their rate of breathing every minute until it returns to the normal resting value.
Blood pH
The pH of the blood is normally 7.35 to 7.45 – a narrow range. During exercise, the concentration of carbon dioxide in the blood and respiring tissues increases. This could lower the pH (making the blood more acidic).
To prevent this happening:
- substances in blood plasma react with the excess carbon dioxide
- increases in the rate and depth of breathing speed up the rate at which carbon dioxide is removed from the bloodstream