Long-distance running changes your brain

 

Well, I think it was pretty obvious that to be a good long-distance runner your brain is different than normal folks, but now we know that it actually changes the brain. But it can get better if you give it time.

Marathon Running Reduces Brain Myelin, But It Fully Recovers

Marathon running temporarily reduces brain myelin content, but levels fully recover within two months.

"Marathon running is the ultimate test of human endurance, pushing the body to its metabolic limits over a grueling distance of 42 km. During a marathon, runners predominantly rely on carbohydrates, particularly glycogen stored in their muscles, as the primary source of energy. However, as glycogen reserves become depleted over the course of the race, the body gradually shifts to utilizing fat as fuel. This metabolic transition is essential for maintaining energy levels during prolonged exercise, but it also poses a challenge for the brain – which typically relies on glucose as its primary energy source."

"Scientists are now suggesting that the brain may adapt to this energy deficit by utilizing myelin lipids as an alternative fuel. Myelin is a fatty substance that surrounds and insulates nerve fibers in the brain and spinal cord, forming a sheath that facilitates the rapid transmission of electrical signals between neurons. Composed of approximately 70–80% lipids, myelin has traditionally been understood as purely structural and insulating. However, animal studies have hinted at a dual function: under extreme metabolic stress, myelin lipids may be mobilized to sustain neural function. Yet, whether this phenomenon occurs in humans during endurance exercise has remained unclear."

"The study revealed a consistent reduction in MWF in 12 areas of white matter, with the most significant reductions – up to 28% and 26% – observed in the pontine crossing and corticospinal tracts, respectively. The affected areas are vital for motor function and integrating sensory and emotional inputs, highlighting a potential impact on movement and emotional regulation."

" “The signal for myelin water fraction – a surrogate of myelin content – is substantially reduced upon marathon running in specific brain regions but recovers within two months. These findings suggest that brain myelin content is temporarily and reversibly diminished by severe exercise,” said the authors."

But is it bad?  That's not clear yet.

"The ability to draw on myelin lipids may support brain function during endurance challenges, but repeated depletion and restoration of myelin could have long-term consequences, particularly in athletes who frequently engage in prolonged, strenuous activities. Individuals with neurological vulnerabilities, such as those predisposed to demyelinating diseases, might also face increased risks if myelin is routinely used as an energy reserve. While the reversible nature of MWF reduction is reassuring, it remains unclear whether repeated cycles of depletion and recovery could lead to cumulative damage or impaired remyelination over time."

I wonder if they should change the name of "Heartbreak Hill" in the Boston Marathon to "The Myelin Mile"?  

Probably not.