Think about the most mentally sharp person in your life. The colleague who always seems focused in meetings, the friend who remembers every detail, or the neighbor who somehow balances a demanding career with endless energy.
There’s a good chance they share one habit: they run.
That connection may sound like a coincidence, but a growing body of research suggests aerobic exercise—especially activities like running—can have measurable effects on the brain, improving memory, learning, and overall cognitive function.
One key factor is a protein called brain-derived neurotrophic factor, or BDNF. Aerobic exercise significantly increases BDNF levels, which help neurons grow and form new connections in the brain. Researchers sometimes refer to BDNF as “fertilizer for the brain” because it supports the brain’s ability to adapt, learn, and build new neural pathways.
Running appears to influence one brain region in particular: the hippocampus, which plays a central role in memory and learning.
In other words, the brain becomes better at learning when BDNF levels increase.
Researchers have become particularly interested in this finding because the hippocampus is among the first brain regions to shrink during normal aging. Exercise may help slow that decline, too.
Mental health may also be part of the equation. Researchers found that exercise is an effective form of therapy for mild to moderate depression, a condition that can significantly affect productivity and concentration.
Together, these effects help explain why people who run regularly often report feeling mentally sharper, more focused, and more resilient under stress.
Of course, you don’t have to train for a marathon to see benefits. Many studies suggest that moderate aerobic activity performed consistently—whether running, brisk walking, or cycling—can produce measurable cognitive improvements.
So the next time you see someone heading out for a run, they may not just be working on their physical endurance. They may also be strengthening the neural pathways that help them think, learn, and remember. And that might explain why the smartest person you know is always lacing up their running shoes.