Because skeletal muscle contractions demand large quantities of atp, skeletal muscles have

Skeletal muscle contractions do in fact demand large quantities of ATP (adenosine triphosphate), the universal source of cellular energy. In order to accommodate this necessity, skeletal muscle cells (myocytes) are packed with mitochondria, which are the energy powerhouses of the cell.

However, the production of ATP would halt in mitochondria if the necessary substrates (fuels) are not present to enter these organelles, mainly glucose and oxygen (O2). So, additionally, skeletal muscle is also loaded with glycogen, a storage form for glucose (as starch), and myoglobin, an enzyme similar to hemoglobin in that it binds an O2 to hold it for use during contraction.