What Happens to Your Brain When You Exercise?

Exercise changes the brain on several timescales at once: within minutes, over weeks, and over years. Some effects are easy to feel, like the lift in mood after a run. Others only show up in brain scans.

During and right after a workout

Physical activity increases blood flow to the brain and raises levels of chemical messengers such as dopamine, serotonin and noradrenaline, which are involved in mood, motivation and attention. The calm, upbeat feeling after exercise was long credited to endorphins. Newer research points to endocannabinoids as well, the body's own cannabis-like compounds, which cross into the brain more easily.

Studies of children and adults show that attention and working memory are often sharper for an hour or two after moderate exercise, which is why some schools schedule activity breaks before lessons.

On a walk

Walking seems to have a specific effect on creative thinking. In 2014, Stanford researchers Marily Oppezzo and Daniel Schwartz asked people to come up with new uses for everyday objects. Participants produced about 60 percent more ideas while walking than while sitting, whether they walked outdoors or on a treadmill facing a blank wall. The boost carried over briefly to sitting down again afterward.

Over weeks and months

Regular aerobic exercise raises levels of brain-derived neurotrophic factor, or BDNF, a protein that supports the growth and survival of neurons. It's especially active in the hippocampus, a region central to memory. In a well-known trial published in 2011, older adults who walked briskly three times a week for a year saw their hippocampus grow by about 2 percent. That roughly reversed one to two years of normal age-related shrinkage. A comparison group that did only stretching saw it shrink.

For mood and mental health

Exercise is now considered a real treatment option for depression, not just a lifestyle tip. A large 2024 review in the BMJ, pooling more than 200 trials, found that walking or jogging, yoga and strength training all reduced depressive symptoms, with more vigorous activity producing larger effects. Exercise can complement other treatment, and anyone with significant depression should talk to a doctor rather than rely on it alone.

Over decades

People who stay active through midlife have a lower risk of dementia in observational studies. Proving cause and effect is harder, since healthier people may simply exercise more. But the biological evidence from blood flow, BDNF and brain volume points in the same direction.

Does the type of exercise matter?

Most of the research focuses on aerobic exercise like walking, running and cycling. But strength training seems to benefit the brain too. Trials in older adults have found improvements in memory and executive function, the skills involved in planning and switching between tasks, after several months of resistance exercise. Activities that combine movement with learning and coordination, such as dance, tai chi and racket sports, are being studied as a way to get both physical and mental challenge at once, with some promising early results.

Children and learning

Studies of school-age children have found that physical activity is linked with better attention and classroom behavior, and short activity breaks during lessons don't take away from academic performance despite reducing teaching time. The U.S. Centers for Disease Control and Prevention recommends an hour of moderate to vigorous activity a day for children and teenagers.

How much is enough?

The World Health Organization recommends 150 to 300 minutes of moderate activity a week for adults, or 75 to 150 minutes of vigorous activity, plus muscle-strengthening on two days. Many of the brain studies used doses around the lower end of that range. There's no clear evidence that one time of day is better than another, so the best time is whichever you can stick to.

Exercise, sleep and stress

Some of exercise's effect on thinking may come indirectly. Regular physical activity helps people fall asleep faster and spend more time in deep sleep, and sleep is when the brain consolidates memories and clears waste products. Exercise also changes how the body responds to stress: people who are physically fit tend to show a smaller rise in stress hormones such as cortisol when faced with a stressful task. Better sleep and a calmer stress response both make it easier to concentrate and learn.

A brain-friendly week

• Three or four brisk walks or bike rides of 30 to 45 minutes, outdoors if possible
• Two short strength sessions using body weight, bands or weights
• One activity that involves learning a skill, such as a dance class, a new sport or tai chi
• Short walks during the working day, especially when you're stuck on a problem

The useful takeaway is that you don't need an intense program. Most of the brain benefits in these studies came from moderate activity like brisk walking.