This 2023 review explains how the physical structure of mitochondria influences their ability to produce energy. Inside mitochondria, the inner membrane folds into structures called cristae, which contain the machinery responsible for generating ATP. The amount and density of these folds play a major role in determining how much energy a cell can produce.

As energy demand increases, mitochondria appear capable of building more densely packed inner membranes, allowing more electron transport proteins and ATP synthases to fit inside the organelle. This can improve ATP production and metabolic capacity. However, the paper also suggests there is a limit: if the membrane becomes too densely packed, mitochondria may struggle to manage proton flow efficiently and begin producing excessive reactive oxygen species (ROS), potentially contributing to dysfunction and oxidative stress.

Importantly, endurance-trained athletes tend to have greater cristae density and more organized mitochondrial structure than sedentary or metabolically unhealthy individuals. The findings support the broader idea that mitochondrial health is not just about the number of mitochondria present, but how well their internal structure adapts to energetic demand.