Response to exercise — AQA GCSE Biology
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Response to exercise explained
Exercise increases the rate of respiration in muscle cells because more energy is needed for muscle contraction.
Read the full explanation
The body responds to this increased demand in several coordinated ways. Heart rate and breathing rate increase, and breathing becomes deeper, so more oxygen enters the blood and more carbon dioxide is removed. Blood vessels supplying muscles widen, increasing blood flow and glucose delivery, while other vessels may narrow. Glycogen stores in muscles are broken down to glucose for respiration. If oxygen supply cannot keep pace, anaerobic respiration supplements aerobic respiration and lactic acid builds up, causing muscle fatigue. After exercise, breathing and heart rate remain elevated to repay the oxygen debt and remove lactic acid.
Your focus
- Describe the changes in heart rate, breathing rate and breathing depth during exercise.
- Explain how increased blood flow and glycogen breakdown support muscle respiration.
- Explain the role of anaerobic respiration and oxygen debt during and after exercise.
Response to exercise exam tips
Marking Points
- Exercise increases the demand for energy in muscle cells.
- Heart rate and breathing rate increase during exercise.
- Breathing becomes deeper, increasing oxygen uptake and carbon dioxide removal.
- Blood flow to muscles increases through widening of blood vessels supplying muscles.
- Glycogen in muscles is converted to glucose for respiration.
- If oxygen supply is insufficient, anaerobic respiration occurs and lactic acid builds up.
- After exercise, increased breathing and heart rate help repay the oxygen debt and remove lactic acid.
Examiner Tips
- 💡Link each body response to its purpose, such as increased heart rate delivering more oxygen and glucose to muscles.
- 💡Use the term oxygen debt when explaining why breathing and heart rate stay high after exercise.
- 💡Describe changes in both rate and depth of breathing, and in blood flow to muscles, to show a full response.
Common Mistakes
- Saying the body stops respiring anaerobically as soon as exercise begins; correct this by stating that anaerobic respiration supplements aerobic respiration when oxygen supply is insufficient.
- Confusing oxygen debt with a lack of oxygen in the lungs; correct this by describing oxygen debt as the extra oxygen needed after exercise to remove lactic acid.
- Thinking only heart rate changes during exercise; correct this by including increased breathing rate and depth, and increased blood flow to muscles.