Participants ranged in age from 45 to 73, suggesting that even older brains remain remarkably adaptable. “Nobody foresaw that this would happen, that the structure of our brain may change so rapidly, in the time which it takes you to run the marathon,” says Matute.
Matute doesn’t believe the temporary drop in myelin leads to noticeable cognitive changes. He suspects the brain routinely taps into myelin for fuel, just at levels too low to detect—except during extreme events like a marathon.
LIMITED TIME OFFER
Discover More, Spend Less
With new subscriber-exclusive stories published daily and complete archive access, your opportunities to explore are endless!
But there’s no need to panic, he says. The changes were short-lived—and may even be healthy. “You exercise everything, including your myelin metabolism,” he says.
What running does to your brain
Running has long been linked to brain benefits. It boosts mood-regulating chemicals like dopamine, serotonin, and norepinephrine, which can ease anxiety and depression. That famous “runner’s high,” once chalked up to endorphins, may come from endocannabinoids—the brain’s natural version of cannabis.
(Here’s how to get high on your hormones—naturally.)
You May Also Like
Aerobic exercise also seems to spur the birth of new neurons in the hippocampus, the brain region critical for memory and learning. Over time, these changes may protect against cognitive decline.
Marathon running has been studied less than running in general, but some studies show these trends hold up over 26 miles. One study reported that some regions of the hippocampus were larger in marathon runners than in healthy controls. Astrid Roeh, a physician at the University of Augsburg, found that marathon runners exhibited fewer depressive symptoms than sedentary people over six months and reported the best moods the day after the marathon.
(Humans were built for long-distance running.)
In another study, Roeh found that marathon running led to changes in the brain’s electrical activity, as measured by electroencephalogram (EEG). Like Matute’s findings in myelin, these changes were transient. “The changes in EEG patterns indicate that there are alterations in how neural circuits are functioning and communicating,” she says.
This reorganization in response to experience is called neuroplasticity. She hypothesizes that regular physical activity may prime the brain for plasticity. “If someone is already physically active, then intense challenges like a marathon might have a stronger — or at least more coordinated — neuroplastic effect,” she says. “The system is ready to respond more effectively.”