Muscles need energy to contract. While exercising, the muscles need additional energy. Several changes take place in the body to enable this:
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:
This build-up of lactic acid produces an oxygen debt.
As body stores of glycogen become low, the person suffers from muscle fatigue.
|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|