Muscle Fatigue

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Muscle Fatigue
How muscles get the energy they need to work
Respiration is the process of releasing energy form the breakdown of glucose. It takes place
in every living cell and this produces energy they require.
During exercise, the muscle cells respire more than at rest. This is because the muscle is
working and contracting more frequently and at a higher intensity. During rest or light
exercise, our bodies use aerobic respiration. It is the most efficient way to release energy
from glucose.
When a muscle is working, oxygen and glucose is needed to give energy to it. These are
also required quicker if the muscle is contracting quicker. Carbon dioxide must be removed
at the same rate as oxygen and glucose is given. This is achieved by increasing breathing
rate and heart rate.
Glucose is given to the muscles as part of the energy source. Our body has a store of
glucose because of the food we eat. All food has glucose in it and this is used up by our
bodies to provide energy. It is stored in our body until it is needed to be used for anaerobic
or aerobic respiration.
What is muscle fatigue and what causes it
Muscle fatigue occurs during anaerobic respiration. Anaerobic respiration happens when
there is not enough oxygen to provide to your muscles for aerobic respiration. Although
our heart rate and our breathing rate increases, this is not enough to provide to all the
working muscles.
Anaerobic respiration converts glucose to energy without oxygen. It is not an efficient way
to do it because it releases less energy per glucose molecule than aerobic respiration. In
anaerobic respiration the glucose is only partially broken down and lactic acid is therefore
produced. This lactic acid builds up in the muscles which is often painful and makes
muscles tire. The muscles will continue to work although it will be painful and muscle
fatigue will occur. Muscle fatigue is where the muscle cannot longer contract.
Anaerobic respiration equation:
Glucose Lactic acid + energy
Aerobic respiration equations:
Glucose + oxygen carbon dioxide + water + energy

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C6H12O6 + 6O2 6CO2 + 6H2O + energy
The processes that allow a muscle to recover after exercise
After exercising and using anaerobic respiration muscles will have oxygen debt. Oxygen is
needed in the muscles to break down lactic acid molecules. This will need to happen for
aerobic respiration to happen normally. To repay the debt, oxygen will be needed to travel
to the muscles. This happens by breathing rate continuing to be increased.…read more

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