CAIE IGCSE Biology 12.3.7 Removing Oxygen Debt After Exercise
Practise explaining recovery after exercise through continued fast circulation, deeper breathing and liver breakdown of lactic acid.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Exam points
- interpret a recovery graph to locate when oxygen consumption remains above resting level
- explain that a fast heart rate transports lactic acid from muscles to the liver
- link deeper, faster breathing to oxygen for aerobic breakdown of lactic acid
12.3.7—How the oxygen debt is removed after question 1
An athlete monitored their heart rate and breathing rate before, during and after vigorous exercise.
Fig. 6.1 shows the results.
Fig. 6.1
Complete the sentences to describe and explain the results shown in Fig. 6.1.
After exercise, it takes minutes for the athlete's breathing rate to return to its resting rate.
The heart rate decreases by beats per minute between 20 and 40 minutes.
The heart rate and breathing rate do not immediately return to their resting rates because anaerobic respiration has occurred.
Lactic acid has built up in causing an oxygen .
The heart rate remains high to transport lactic acid to the .
The breathing rate remains high to supply for the respiration of lactic acid.
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