Response to exercise
Muscles need energy to contract. While exercising, the muscles need additional energy. Several changes take place in the body to enable this:
- the breathing rate and volume of each breath increases to bring more oxygen into the body and remove the carbon dioxide produced
- the heart rate increases, to supply the muscles with extra oxygen and remove the carbon dioxide produced
If insufficient oxygen is available to the muscles, for instance the exercise is vigorous and/or prolonged, the heart and lungs are unable to supply sufficient oxygen. Muscles begin to respire anaerobically. Lactic acid is produced from glucose, instead of carbon dioxide and water. Muscles continue to contract, but less efficiently.
During long periods of vigorous activity:
- lactic acid levels build up
- glycogenAnimals store glucose as glycogen in their liver and muscle tissues. reserves in the muscles become low as more glucose is used for respiration, and additional glucose is transported from the liver
This build-up of lactic acid produces an oxygen debtThe amount of extra oxygen required by the body for recovery after vigorous exercise..
As body stores of glycogen become low, the person suffers from muscle fatigue.
Aerobic and anaerobic respiration compared
| Aerobic respiration | Anaerobic respiration | |
| Presence of glucose | Present | Absent or in short supply |
| Oxidation of glucose | Complete | Incomplete. The products of respiration still contain energy. |
| Products of respiration | Carbon dioxide and water. The products do not contain stored chemical energy. | Mammalian muscle - lactic acid. Plants and microorganisms - ethanol and carbon dioxide. The products still contain stored chemical energy. |
| Amount of energy released | Relatively large amount | Small amount |
| Presence of glucose | |
|---|---|
| Aerobic respiration | Present |
| Anaerobic respiration | Absent or in short supply |
| Oxidation of glucose | |
|---|---|
| Aerobic respiration | Complete |
| Anaerobic respiration | Incomplete. The products of respiration still contain energy. |
| Products of respiration | |
|---|---|
| Aerobic respiration | Carbon dioxide and water. The products do not contain stored chemical energy. |
| Anaerobic respiration | Mammalian muscle - lactic acid. Plants and microorganisms - ethanol and carbon dioxide. The products still contain stored chemical energy. |
| Amount of energy released | |
|---|---|
| Aerobic respiration | Relatively large amount |
| Anaerobic respiration | Small amount |
