Most people start exercising to get stronger, perform better, or change how they look and feel. Very few start because they want or expect brain improvements.
But the brain benefits are, in fact, real. Exercise can help ease symptoms of depression. Regular training is linked to modest gains in thinking skills like attention and planning. And active people tend to have a lower risk of dementia later in life.
So even though your brain may not be the reason you train, I’ll assume that you’d still appreciate collecting those benefits along the way.
The catch is that at least one part of the brain seems to respond less to whether you show up and more to whether you’re actually getting fitter. (Because showing up pays off in its own ways, it’s easy to start treating it as the whole job. During a tired or stressful period, it can be. But if you’ve been consistent for months without getting any fitter, something about the type or difficulty of the training needs to change.)
Showing up wasn’t the difference
In a yearlong study published in 2011, researchers took previously sedentary adults, ages 55 to 80, and split them into two groups. One group walked, building up to 40 minutes three times a week. The other did a supervised stretching-and-toning program three times a week.
Both groups were instructed to train at relatively challenging levels. The walkers moved briskly enough that carrying on a conversation took some effort. The second group worked at a level that would be considered “somewhat hard” to “hard” on a common rating of perceived exertion (RPE) scale.
Attendance was nearly identical. But by the end of the year, the walkers’ hippocampus—a part of the brain that is associated with memory and normally shrinks with age—had grown by about 2%. The stretching-and-toning group’s had shrunk by about 1.4%—roughly a normal year’s worth of age-related loss.
Getting fitter was
The clearest difference between the groups showed up in aerobic fitness. On average, the walkers improved theirs by nearly 8%. The stretching-and-toning group improved by about 1%.
To be clear, “fitter” here means aerobically fitter. The study didn’t measure strength, so the stretching-and-toning group may well have gotten stronger—we just don’t know. Their program simply didn’t keep heart rates up long enough to drive much of an aerobic adaptation. (That’s not an argument against strength training. It’s a reminder that different kinds of fitness come from different kinds of training, which is why it pays to work on more than one of them on purpose.)
Fitness gains also varied a lot from person to person in both groups. The study didn’t look at why, but the usual suspects are familiar: nutrition, sleep, stress, and effort that feels hard without being physically hard. (Unfamiliar or uncomfortable exercises can feel demanding while asking relatively little of your heart and lungs. Remember RPE? That’s rating of perceived exertion—which is not necessarily the same as actual exertion.)
Ultimately, across both groups, the people whose aerobic fitness improved more tended to show more growth in the hippocampus. It’s an association rather than proof, but it points in a useful direction: the brain changes followed the fitness changes, not the attendance sheet.
Putting it into practice
If you’re not exercising regularly yet: the study’s walking program is a reasonable place to start. Work up to 40 minutes, three times a week, at a pace where you’re breathing hard enough that holding a conversation takes some effort. Doing some strength training would also be good from a multi-benefit standpoint—but starting with what you’re confidently able to do consistently is the most important first step.
If you already train: consider whether anything in your week keeps your heart rate up for an extended stretch. Strength training is great, but pure strength work—heavy weights, low reps, long rest—mostly spikes your heart rate briefly after each set and lets it settle back down. If that describes most of your training, adding some long, slow distance or power repeats (short, explosive sets on a tight clock—like 5 swings every 30 seconds for 30+ minutes) a couple times per week would move you in the right direction.