I've recently been on a TV show called “To Live, I Run.” It's a show that brings together a group of novice runners and challenges them to run a 42-kilometer full marathon, and I'm one of the runners thought to be unable to do it. First, I’m challenged to run 5 kilometers, then 10 kilometers, and once I finish, I move on to the next challenge. I even competed in an official 10-kilometer marathon and completed it, which was so successful that I now practice running the same distance every few days.

Last week, for the first time in my life, I practiced running over 20 kilometers. But before I did it, my brain told me “No way” and flooded me with all sorts of worries and anxieties, like “What if I get injured?” I have allergic asthma—running is a risky activity that can cause breathing difficulties. I have some issues with the ligaments in my knees and a herniated disc in my back, and if I abuse my body, I might not even be able to walk someday. A lot of very logical and rational reasons went through my head, and I truly felt like I shouldn’t run.

The reason for the brain’s excuses is simple. First, the brain prioritizes survival and protection. It doesn’t favor activities that rapidly increase energy expenditure -- unless you’re in real danger and need to run. The amygdala and the hypothalamic-pituitary-adrenal (HPA) axis are largely responsible for the “anxiety” and “stress” that keep us from entering potentially dangerous situations. On top of that, the brain always makes judgments based on past experiences. So if you’ve never run a long distance before, it will naturally label it as “impossible” or “too much.” This anxiety, stress, and judgment that the choice is risky or difficult also affect your physical state -- your muscles tense up, your body feels fatigued, and it suddenly becomes a struggle to move your legs, making you just want to stop and crawl back into bed.

The way to change the brain is through action. Tense muscles relax through stretching, and once you take a deep breath and start running, every moving part of your body sends new signals to your brain. Your heart rate increases, your blood metabolizes more rapidly, your lungs work harder to supply oxygen, and your cerebellum processes signals related to balance and movement. Meanwhile, your muscles signal that you’re already in motion. Once the brain recognizes that you're moving, it shifts gears to help you succeed. It activates the sympathetic nervous system and begins coordinating different parts of the body to prevent injury and maintain performance. As part of this process, it also increases the production of the stress hormone cortisol.

Once you’ve run 10 kilometers, then 20 kilometers, the data in your brain is updated. Because you’ve experienced something you hadn’t done before, your perceived capabilities shift, and running the same distance feels “possible” or “doable” the next time. Interestingly, as the brain’s self-assigned limits expand through exercise, the areas responsible for anxiety and stress also adapt. In similar situations, the stress hormone cortisol is significantly reduced, and you feel far less anxious and stressed. So, as you continue to challenge yourself, you not only increase your energy levels but also expand your belief in what you’re capable of.

Some people turn to alcohol when they feel anxious or afraid. That’s because alcohol activates the neurotransmitter GABA (gamma-aminobutyric acid) in the brain. GABA works by inhibiting the activation of nerve cells, which is why alcohol has a calming effect on anxiety. Interestingly, sustained physical activity -- like running, swimming, or cycling -- also increases GABA activity in the brain. This means regular exercise can be an effective way to manage anxiety or fear without resorting to alcohol.

If you’re anxious or worried about accomplishing something you really want to get done, try running, swimming, or cycling. Your brain can overcome anxiety and fear by updating the information it has about your physical capabilities. If you want to change your brain, get moving. Just move! Get out there and run!

Chang Dong-seon is the CEO of Curious Brain Lab and resides in Seoul. He studied Biology at Uni Konstanz, Neuroscience at the International Max Planck Research School, and Cognitive Science at Rutgers University. Chang's career includes roles as an Assistant Professor at Hanyang University and a Researcher at the Max Planck Institute for Biological Cybernetics. He also served as the head of the Future Technology Strategy Team at Hyundai Motor Group. His extensive expertise spans biology, neuroscience, and cognitive science. This column was originally published in Segye Ilbo in Korean on May 1, 2025. -- Ed