Energy is generated in mitochondria

Mitochondrion in the electron microscopeThe muscle fibers need "fuel" to contract - because movement is known to cost energy.
Metabolism and energy

The nutrients supplied by the blood contain energy, but this energy is chemically bound and is not directly available to the cells. Just like gasoline in an engine, nutrients must first be burned to produce movement. This happens in special cell organs, the mitochondria, which are present in every muscle cell.

Because of their function as energy suppliers, "the mitochondria are also called the power plants" of the cells.

Mitochondria in the sarcomereThe energy gained by burning the nutrients is initially stored in a special molecule, theAdenosine triphosphate (ATP). The ATP then migrates from the cell power plants to the myofibrils, the smallest units of the muscle in which the movement is generated. There, the ATP releases the stored energy the moment the muscle contracts: Physical training increases the number of myofibrils and thus the thickness and strength of the muscle. The mitochondria - cell power plants - can also be increased through training (especially endurance training) and thus improve the energy supply.