You already know that exercise is great for your mind as well as your body. Now brain researchers are uncovering exactly how exercise helps our brains learn and, more importantly, how best to retain what we’ve learned.

Exercise is key. But it’s all in the timing.

To evaluate the new research, we spoke with cognitive health expert and frequent Bottom Line contributor Cynthia Green, PhD, president and CEO of Total Brain Health and TBH Brands.


Researchers in the Netherlands asked 72 volunteers to learn 90 picture-location associations in a 40-minute exercise. The researchers did noninvasive brain scans to see how the different parts of the brains lit up.

Then the researchers asked about one-third of the volunteers to exercise immediately afterward…another third to exercise four hours later…and a third group to not exercise at all. The exercise was a garden-variety aerobic workout—35 minutes of interval training on an exercise bike, at an intensity of up to 80% of maximum recommended heart rate for each individual.

Then, two days later, all the volunteers were asked to repeat the task to see how well they retained what they had learned. They repeated the brain scans, too.

Results: Exercising immediately after didn’t help—those folks didn’t retain knowledge any better than those who didn’t exercise at all. But the ones who exercised four hours later did significantly better than everyone else at retaining what they’d learned.

What happened inside their brains was even more interesting. For those who delayed exercise for four hours, the hippocampus—a part of the brain crucial to long-term memory—looked remarkably similar during the initial learning task and the one repeated two days later when they got correct answers. It lit up in the same pattern. For the other volunteers, not so much—when confronted with the same task again, they had to, in essence, relearn much of what they had learned earlier.

While this experiment didn’t examine physiology directly, the researchers note that other studies have found that exercise boosts brain chemicals known as catecholamines, including dopamine and norepinephrine, which are key to memory and learning. Still, they’re not sure why waiting four hours made a big difference. That’s where future research will go. The study also didn’t look at what happens if you exercise, say, two or three hours after learning something—or five. For now, all they know is that getting some aerobic exercise about four hours later helps you remember.


Dr. Green is all for using the new research to help you consolidate learning. The next time you need to make sure new information sticks—when you’ve just immersed yourself in a big new work project—try heading to the gym or lace on your running shoes and go out for a jog four hours later, she suggests.

But Dr. Green also wants us to see the big picture when it comes to exercise and our brains. “We know exercise overall is one of the best things we can do for our brains, and studies have repeatedly demonstrated that aerobic activity benefits cognition,” she said. Regular aerobic exercise—a rough total target of 150 minutes a week—is also key to maintaining cognitive health as you age, and it helps prevent dementia. But there’s also growing evidence that strength training is also important for maintaining cognitive performance.

In other words, even if you don’t care how buff you look, if you value your brain, when it comes to exercise—just do it. And to learn more ways to stay sharp, see Dr. Green’s suggestions on the best ways to keep your brain buff.