Muscular activity requires continuous energy flow for it's
effective working.
- At first muscles utilizes glucose that stored in muscles.
Muscles have less quantity of glucose stores. So that it goes for
another method of ATP supply.
- Muscles have a short-term store of energy in the form of
creatine phosphate which is generated from ATP and can regenerate
ATP when needed with creatine kinase.
- Another form of glucose stored in muscles is glycogen. When
required this glycogen undergoes metabolism to provide ATP.
- Within the skeletal muscles some amount of glucose metabolizes
anaerobically which produces two ATP and two lactic acid
molecules.
- Muscle cells also contain globules of fat, which are used for
energy during aerobic exercise.
So many methods are evolved to produce ATP for muscles during
activity, because single method does mot produce sufficient energy
for efficient muscle activity. So it utilizes many methods.