Muscles require a large amount of energy to function. This is provided primarily by mitochondria in cells that consume a lot of energy. We therefore find more of these powerhouses of the cell in muscle cells than in other cell types with a lower metabolic rate. Scientists at the Max Planck Institute for Heart and Lung Research in Bad Nauheim have now identified a mechanism that can be used to regulate the development of mitochondria in muscle cells. This is what makes the endurance capacity of muscles even possible in the first place.