Does the Hulk use energy for strength?

I was wondering if the hulk's muscles work like a regular persons. Like is he strong because of his muscle's size or does he use energy like superman to power his muscles. I was thinking this because superman metabolizes yellow sun solar energy to power his muscles so they don't have to be that big (he looks like a regular in shape guy) but the hulk is an inhuman size so is his strength due to his inhuman size or some type of metabolized Gama-radiation energy.