How Does the Marathon Affect the Brain? New Study Offers Insight

Recent research on marathon runners found a reduction in an important brain substance called myelin after the race.
Running May Fight the Onset of Brain Rot.

There’s a breadth of research on cognitive function and exercise that suggests the benefits of physical activity can have profound advantages for your brain. For example, a research review in Comparative Physiology noted that exercise, in conjunction with a healthy diet, may help prevent neurological and cognitive disorders. And the Centers for Disease Control and Prevention reports that physical activity can be a boon for problem solving, emotional balance, learning, and memory.

However, a new study in Nature Metabolism has results that seem to contradict those findings: Researchers noted that marathon running can deplete a crucial brain substance for motor coordination, as well as sensory and emotional regulation.

That might sound alarming, but there’s good news: The process may actually be beneficial for long-term brain health.

Researchers did magnetic resonance imaging (MRI) on 10 runners, ages 45 to 73, both 24 and 48 hours before and 24 and 48 hours after a marathon and found a substantial reduction in myelin water fraction, which is an indication of overall myelin content, said study co-author running a marathon., researcher in the department of neurosciences at the University of the Basque Country in Spain. They also did an MRI two weeks after the marathon on two participants and two months after on six participants. (Keep in mind this was a small study!)

Myelin is a fatty substance that insulates nerve fibers in the brain and spinal cord, and makes up about 40 percent of the brain’s white matter—the type of tissue in the brain responsible for nerve signaling, which enables motor control, cognition, learning, memory, and sensory perception.

In addition to prompting faster transmission of nerve impulses (which can help you move more quickly or learn with better focus), myelin plays a role in helping convert glucose into energy for the brain. This is incredibly important, considering the brain needs very high energy for all those nerve signals—especially when The study author explains how this may actually benefit cognitive health, rather than harm it.

The reason the brain turns to myelin during extreme exercise like running marathons: energy. As explained in the research, marathon runners rely on carbs as the main energy source during a race. When your glycogen (the stored form of glucose) runs out, you turn to fat as fuel. Similarly, when your brain runs out of glucose, the researchers hypothesize that it turns to these myelin lipids for energy.

Why Strength Training Is Crucial for Older Women previous studies have shown that lower myelin content in the brain is linked to cognitive decline, especially in areas related to verbal fluency and executive function.

So does that mean runners should be concerned about the depletion of myelin content? No. In fact, Matute said the opposite is true: Consider myelin breakdown a perk of endurance exercise that optimizes how your myelin functions. Plus, myelin regenerates within a couple months, and sometimes within two weeks, as shown in these results.

“This should not at all be seen as a negative result,” Matute explained. “That’s because it’s likely that using and replenishing these myelin lipids is beneficial, because it exercises the brain’s metabolic machinery. Also, any alterations that do occur are very subtle and in our research, we found they’re reversible.”

In other words, the brief myelin reduction could be similar to how muscles react to strength training: Muscle fibers break down and get depleted of muscle glycogen, but that process optimizes function in the long run. Also, you can mitigate the effects of that depletion going too far—in strength training, overdoing it can lead to longer recovery times and potentially non-reversible effects—through effective pre and postworkout fueling. the Centers for Disease Control and Prevention reports.

“In principle, carbs and better fueling help sustain the effort and may possibly reduce the amount of myelin lipids used,” he said. “In our research, some participants took carbs during the marathon and some didn’t fuel [at all], and there didn’t seem to be any differences between them. But we need to examine this in the future.” For example, eating more carbs during or after a marathon might shorten the duration of myelin reduction, but that’s a question for future research.

Another variable that’s still in play is running speed, which wasn’t looked at in this study, he said. The research team is looking into the possibility that running faster—particularly if you’re underfueled—might exacerbate the reduction in brain myelin.

But even if those factors turn out to change the timeframe of myelin reduction, Matute said it’s likely those would be minor considerations.

“The fact is that brain myelin reduction is rapidly reversed,” he explained. “Also, the biggest takeaway here is that this is just one more way that an activity like marathon running can help your brain function. All of the researchers are runners—I’ve done 18 marathons myself—and none of us plan on stopping.”