Metabolism of Muscle Tissue
➢ Chemical energy in the body is obtained via metabolism of adenosine
triphosphate (ATP) to adenosine diphosphate (ADP).
➢ If the energy requirement is short-term, the ADP is converted back to
ATP. However, this process is too slow to keep up with energy
demands during long-term and intensive exercise, thus consumption of
other fuels is necessary.
➢ Muscle tissue consumes significant amount of nutrients and oxygen.
✓ However, this depends on how intensively the muscle is working. For
1
, instance, during intense exercise, aerobic metabolism in the muscles account for 60
% of total oxygen consumption. Muscle cells are also capable of functioning for a
long period of time without oxygen (anaerobic metabolism)
➢ The main sources of fuel for muscles are carbohydrates (glycogen) and
lipids (free fatty acids in plasma).
➢ Carbohydrates can be metabolized either in the presence of oxygen
(aerobically) or in its absence (anaerobically), however, lipids can only
be metabolized aerobically.
➢ During light exercise or when the body is at rest, muscle metabolism
is usually entirely aerobic, and the source of fuel is the free fatty acids
in plasma.
, ➢ During intense exercise, metabolism of the fatty acids cannot keep up
with the demand, and glycogen is used for energy.
➢ However, as intense exercise continues, glycogen stores are exhausted,
and free fatty acids become the principal source of energy2 .
➢ Trained athletes have an increased ability to metabolize fatty acids as
compared with sedentary people; this permits athletes to exercise
longer and at higher work rates than untrained people.
➢ Muscle glycogen stores can be increased by carbohydrate loading, a
dietary practice used by elite athletes to maximize the storage of
glycogen in the muscles and liver.
➢ In this case, carbohydrates are eaten a few days prior to an event.
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➢ Chemical energy in the body is obtained via metabolism of adenosine
triphosphate (ATP) to adenosine diphosphate (ADP).
➢ If the energy requirement is short-term, the ADP is converted back to
ATP. However, this process is too slow to keep up with energy
demands during long-term and intensive exercise, thus consumption of
other fuels is necessary.
➢ Muscle tissue consumes significant amount of nutrients and oxygen.
✓ However, this depends on how intensively the muscle is working. For
1
, instance, during intense exercise, aerobic metabolism in the muscles account for 60
% of total oxygen consumption. Muscle cells are also capable of functioning for a
long period of time without oxygen (anaerobic metabolism)
➢ The main sources of fuel for muscles are carbohydrates (glycogen) and
lipids (free fatty acids in plasma).
➢ Carbohydrates can be metabolized either in the presence of oxygen
(aerobically) or in its absence (anaerobically), however, lipids can only
be metabolized aerobically.
➢ During light exercise or when the body is at rest, muscle metabolism
is usually entirely aerobic, and the source of fuel is the free fatty acids
in plasma.
, ➢ During intense exercise, metabolism of the fatty acids cannot keep up
with the demand, and glycogen is used for energy.
➢ However, as intense exercise continues, glycogen stores are exhausted,
and free fatty acids become the principal source of energy2 .
➢ Trained athletes have an increased ability to metabolize fatty acids as
compared with sedentary people; this permits athletes to exercise
longer and at higher work rates than untrained people.
➢ Muscle glycogen stores can be increased by carbohydrate loading, a
dietary practice used by elite athletes to maximize the storage of
glycogen in the muscles and liver.
➢ In this case, carbohydrates are eaten a few days prior to an event.
3
