Marathon runners experience reversible changes in their brain myelin. These findings indicate that myelin (a substance that surrounds the neurons) exhibits behavior that was previously unknown, and that it contributes towards the brain's energy metabolism when other sources of energy are running low. Understanding how myelin in the runners recovers quickly may provide clues for developing treatments for demyelinating diseases such as multiple sclerosis.
https://www.nature.com/articles/s42255-025-01244-7