With the boom in “running” and running, many rubbing each year with a marathon, long considered the ultimate test – that some people engage in endurance races like ultra -vendors, much more difficult today. But you may be surprised to learn that this performance could be accompanied by an unexpected effect: a cerebral narrowing. In any case, this is what New Atlas magazine suggests.
The study, conducted by the University of the Basque Country and published in the Revue Nature Metabolism on March 24, 2025, highlighted a correlation between the practice of the marathon and a significant decrease in myelin, this protective sheath that surrounds nerve fibers in the brain. Essential to the transmission of electrical signals in the central nervous system, its degradation is a key marker of various neurological pathologies, such as cerebral vascular accidents and multiple sclerosis.
An intense effort for your legs and your brain
When the body exhausts its glycogen reserves, it draws from fat to continue the effort. Problem, myelin, which protects nerve fibers, is made up of 70-80% lipids, a useful resource for the body in full effort. Concretely, running towards the finish line, the marathonists actually burn part of their brain.
In their study, the researchers analyzed the brain MRI of the runners before the marathon, then within 48 hours of the race. The result is clear: they have found a significant drop in myelin in a dozen areas of the brain linked to motor skills, sensations and emotions.
Not a reason to remind your running shoes. Your cerebral cortex is not consuming slowly, and the damage is completely reversible. Other later scanners have shown that myelin went up naturally after two weeks and found its normal level after two months. You are not in danger of death, everything is fine.
Researchers do not yet fully understand the implications of this brain mechanism after the race. Led on only ten runners (including eight men) aged 45 to 73, their study is too limited and establishes a correlation, not causality. More in -depth research is therefore necessary before really understanding the importance of such a mechanism and the possible neurological effects in medium and long terms.
