When Addie Bracy needs a mental reset, she knows just where to head. The pro ultrarunner and certified mental performance consultant hits the Bear Peak or Green Mountain trails near her home in Boulder, Colorado. The natural beauty lifts her mood, while the technical terrain of the hills and canyons demands just enough focus to put a pause on her ruminating.

“You’re always paying attention to your surroundings and your footing,” says Bracy, author of the forthcoming Mental Training for Ultrarunning. “It’s a built-in, positive distraction to keep you present.”

Vanessa Peralta-Mitchell finds her strength and confidence on the roads. Before she signed up for the 2007 Philadelphia Marathon, she wasn’t sure she could do 26.2 miles on foot. A decade and a half later, “I’ve been empowered on and off the pavement to reach even bigger, scarier goals,” she says. Case in point: She noticed women of color were seldom viewed as leaders in the running industry and brainstormed ideas for changing that. Now, she’s not only a certified running coach but also owns her own business dedicated to training and mentoring others.

Then there’s Maggie Montoya, a pro runner with Roots Running in Boulder who also works as a pharmacy technician. As a pre-med student at Baylor University, she’d study her anatomy books, then head out to train. “I remember so many runs that I went over and over the musculoskeletal system, and visualize how all the systems worked together to allow me to run,” she says. She used similar techniques last summer, studying for the MCAT and preparing for pandemic-friendly road and track races.

For each of these runners, and countless others, running serves a purpose beyond training the body. Putting in miles can relieve stress and anxiety, boost confidence and resilience, break creative blocks, and sharpen your recall. These days, therapists recommend running to regulate mood—and some, such as Run Walk Talk founder and licensed clinical social worker Sepideh Saremi, even conduct sessions in motion. One day, doctors might prescribe targeted programs of physical activity to stave off age-related cognitive decline.

Scientists once believed that, unlike muscles and connective tissues, our brains remained pretty much unchanged in adulthood, or at least until they began to fade in our golden years. Now, studies show that isn’t the case; our brains can rewire, adapt, and perhaps even grow in response to our behaviors and experiences. And it appears that exercise in general—and in some cases, walking and running specifically—are among the most powerful ways to reshape it.

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What Rodents Can Teach Us

The idea that running might change our brains isn’t new. In the late 1990s, researchers documented a striking finding. Mice in an enriched environment—a cage with more space, activities like toys and running wheels, and social connections—had brains that were visibly different. Specifically, they sprouted more new neurons in a part of the brain called the hippocampus, critical to learning and memory.

Neuroscientist Henriette van Praag, Ph.D., aimed to figure out exactly which upgrade made the biggest difference. The aha moment came when she compared mice with and without running wheels in their cages. Running seemed to promote the proliferation of two to three times more new brain cells, a process called neurogenesis. And all this was in the dentate gyrus, a segment of the hippocampus more closely tied to cognition than athletic ability.

Since then, van Praag has dedicated her career to studying the beneficial effects of exercise on brain function and behavior while maintaining her own running habit. She logs 10-milers on the weekends and squeezes shorter runs between work in her lab at Florida Atlantic University, where she’s an associate professor of biomedical sciences. She and other scientists can study mice through their whole lifespan, about two years, and actually peer inside their brains to see the way running changes them.

This gives researchers who study humans (and obviously face different ethical and logistical challenges) a road map to follow. While scientists can’t see inside people’s skulls in the same way, tests of electrical activity and blood flow allow them to trace similar effects in people. Plus, human study participants, unlike mice, have the ability to explain how they’re feeling. That makes it easier to assess how your daily miles affect not only learning and memory, but also more complex concepts like mood and creativity.

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Of Blood Vessels and Biochemicals

Scientists today have begun to paint an increasingly accurate picture of the cascading cerebral reactions that kick off soon after you start your GPS watch. First, there’s the matter of blood flow. As your heart pumps harder to fuel your working muscles, more blood—and all the nourishing nutrients it contains—also reaches your gray and white matter.

Meanwhile, your muscles, liver, and other tissues begin secreting compounds called cytokines. At least two—irisin and cathepsin B, which van Praag’s lab has studied in mice—have been linked to better performance on memory tests in humans.

Somewhere in the midst of your strides, you might also feel a surge of endocannabinoids. These biochemicals bind to the same receptors as cannabis, contributing to the euphoria known as “runner’s high.” Natural opioid-like chemicals called endorphins often get credit for this sensation. But more recent research suggests they have less to do with mood than with pain processing, something else that’s altered by running, says Jacob Meyer, Ph.D., assistant professor of kinesiology and director of the Wellbeing and Exercise Laboratory at Iowa State University.

Running also regulates levels of neurotransmitters, tiny chemical communicators that shuttle signals between brain cells. Some, such as dopamine and serotonin, directly influence mood and motivation. Acetylcholine drives the force and duration of each muscle contraction, but it also keeps you focused and alert, says neuroscientist Allison Brager, Ph.D., author of Meathead: Unraveling the Athletic Brain and director of human performance for the Army Warrior Fitness and Esports Teams.

And then there’s brain-derived neurotrophic factor (or BDNF), a chemical credited for mediating many of the longer-term benefits of exercise on brain health. Not only does BDNF likely promote neurogenesis, it appears to keep older brain cells healthy and functioning well, too. Like a gardener, it prunes back connections that are no longer needed and fosters the growth of new synapses. In this way, it may strengthen networks that link the hippocampus to the prefrontal cortex, which controls higher-level functions like decision-making and attention. New memories can then be formed, and new skills acquired.

The human hippocampus also enlarges in response to exercise. According to a landmark 2011 study, older adults who did three cardio sessions a week for a year saw theirs swell to the tune of about 2 percent. But because scientists can’t slice out a section of brain and count the neurons inside it, they can’t yet prove exercise causes neurogenesis in humans.

In fact, much about the exact order and significance of each of these factors remains unclear. “When you think about the way biological systems work, something changes, and then that leads to something else changing,” Meyer says. “Eventually, one day, some area in your brain is slightly larger.” In other words, experts can’t yet see the entire pathway from running to better brain health. But, study by study, they’re mapping out the key neurobiological bricks that build it.

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Reaping Cerebral Rewards

For many runners, the route leads to better mental health and psychological functioning. “The more active people are, the better they feel across different areas,” Meyer says. “They feel less anxious, they feel less depressed, they’re more cognitively stable. They sleep better, they feel less stress.”

That doesn’t mean, of course, that treating a mental health condition is as simple as slipping into your sneakers. But studies do show exercise has beneficial effects against depression and anxiety, and could be even more powerful for those at increased risk or who already have mental health diagnoses. For some, physical activity even works as well as antidepressant medications, and with fewer side effects.

Beyond its neurochemical effects, there are other theories about why running regulates both racing minds and low moods. For anxiety, it may act as a type of exposure therapy: Running produces some of the same physical sensations as extreme fear or a panic attack. Your heart races, your muscles tense, and your breathing turns quick and shallow. But when you’re voluntarily pushing your body, you also learn you have the power to slow down and regain control, Meyer says. When those sensations arise again in other contexts, you might stay calmer.

Getting out the door for a few miles can also interrupt the rumination and negative thought patterns characteristic of anxiety, depression, and other conditions. For 30 minutes or an hour, you’re physically distant from your problems—and if you’re running outside, you’re often surrounded by nature, which can be psychologically soothing. “You’re having the space to just sort of be,” says Karen Bagley, a runner and licensed clinical psychologist at Momentum Psychology and Performance in Woodbridge, Virginia.

That same sort of mindfulness-enhancing escape may also help promote problem-solving and imaginative thinking. As your arms and legs pump, you’re distracted from troubling thoughts. But the motions aren’t so complex that they require your full attention. “It’s that perfect middle space, where you have enough energy left over to be mulling over something that’s gnawing at you,” Saremi says.

Creativity isn’t always easy to pin down in the lab, but researchers have developed innovative ways to quantify it. In one recent Austrian study, participants named alternate uses for common objects like car tires and umbrellas and completed partially drawn lines and figures in an artistic way. Those who tallied more steps on activity trackers the five days before also dreamed up more original possibilities.

Active people also tend to do better with the more straightforward tasks handled by the prefrontal cortex, like memorizing numbers and categorizing new information. The effects are immediate and cumulative, and seem potent to young and old alike. In one study, teens scored higher on the Stroop test—which measures how fast you can think while distracted—after completing a round of 10-second sprints. In another, older adults who regularly ran or did other high-intensity aerobic activities performed significantly better on tests of thinking and memory than those who were sedentary. The difference was enough to counteract about 10 years of aging, the researchers note.

In fact, the results of mouse and human studies alike should be encouraging to newly minted masters runners. Van Praag says she’s tested mice who didn’t get on wheels at all until they were 18 months into their two-year lifespans. “After one month of running, they outperform their sedentary counterparts on learning and memory tests and they have more new neurons,” she says. “It’s never too late to pick up an exercise program, to start running. The benefits are still there.”

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Run Smarter (and Happier)

So how much do you have to run for optimal brain health? “We’re a long way from a perfect prescription,” Meyer says. Specifics likely depend on individuals, including genetics. And the optimal distance and intensity may depend on exactly which neurological advantage you want to maximize.

But research and experience of professionals offer clues. When it comes to boosting mood, any distance or pace will do. In many of his studies, “it didn’t matter how hard someone exercised; if they exercised, they felt better than if they didn’t,” Meyer says. “It was binary.”

Many of the principles that make for an effective training plan also improve your brainpower:

• Stay consistent. Routines that roughly align with the government’s exercise recommendation (three weekly, moderate-intensity workouts of about an hour each, for three months or more) seem most powerful in warding off the cognitive decline and brain changes that come with age, according to a 2019 review in Trends in Cognitive Science.
• Mix it up. Incorporate speedwork and strength training. Some studies suggest that higher-intensity workouts (repeats or tempo runs) might speed reaction times and performance on tasks that involved executive function. Lifting weights appears to improve mental health and memory through different pathways than aerobic workouts.
• Race, when you can. Not only will you reap the benefits of higher-intensity efforts, you’ll also have the chance to practice grace under pressure. “That’s when I think the athlete brain shines, is in the midst of stress and chaos,” Brager says. “You have this sense of peace and calmness that other people don’t, and it comes from being in the height of competition.”

COVID-19 interrupted races and training groups, but it also demonstrated the vital importance of running. In one brand-new study, Meyer and his colleagues found that most people spent less time outside during lockdowns, but those who bucked the trend were less stressed and reported better mental health. In another study, those who were able to stick to an exercise routine during restrictions scored higher on almost every measure of psychological well-being, from stress to loneliness to symptoms of depression.

Results like these don’t surprise ultrarunner Bracy. “Athletes, especially endurance runners, have a capacity for acceptance—for not shoving away things that are unpleasant,” Bracy says. Rather than avoiding difficulty, we lean into it, challenging our bodies and minds by choice so we can step up when it matters. Resilience is wired into our circuitry—because we’ve put it there, step by step.

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Boost Your Brain Power

Here’s how to use running to:

• Break negative thought or behavior patterns. Start an easy run with a few deep, cleansing breaths. Then follow the acronym AIR: awareness, interruption, and replacement. Catch and interrupt the unwanted thought—maybe it’s “I’m not good enough” or “I can’t cope on my own”—right when it starts. Then find a suitable swap.
• Remember key information. Try a protocol used in a Dutch study: Four hours after you learn something new, complete a 35-minute workout with a few harder intervals. Brain scans and follow-up tests showed this improved the encoding of new memories.
• Increase your resilience. Go for a trail run that’s more technical than your normal route. Don’t worry if you trip, encounter a surprise thunderstorm, or find yourself scrambling up an incline. “You have to accept that some level of adversity is going to happen,” Addie Bracy says. “There is less resistance when it does, and more problem-solving.”
• Quiet an anxious mind. Keep your pace easy and your mind in the present. Tune in to internal or environmental sensations, Sepideh Saremi recommends. Count footfalls or breaths, observe the nature around you, or do a body scan, gradually moving your focus from the top of your head to the tip of your toes (or vice versa).
• Boost your mood with speedwork when you’re sad. While slow running can calm you down, faster, higher-intensity running may rev you up, making you feel happier and stronger, Saremi says. Not feeling up to a tempo run or track workout? Research suggests even a short walk may prove uplifting.