Today, you’re going to do perhaps the single best thing for your brain.

When I asked neurologists about their top behaviors for brain health, they all stressed the importance of physical activity.

“Exercise is top, No. 1, when we’re thinking about the biggest bang for your buck,” said Dr. Gregg Day, a neurologist at the Mayo Clinic.

Numerous studies have shown that people who exercise regularly tend to perform better on attention, memory and executive functioning tests. There can be a small cognitive boost immediately after a workout, and the effects are sustained if people exercise consistently. And while staying active can’t guarantee you won’t develop dementia, over the long term, it is associated with a lower risk of it.

Researchers think that moving your muscles benefits your brain in part because of special signaling molecules called exerkines. During and after a workout, your muscles, fat and other organs release these molecules into the bloodstream, some of which make their way up to the brain. There, those exerkines go to work, helping to facilitate the growth of new connections between neurons, the repair of brain cells and, possibly, the birth of new neurons.

Exercise also appears to improve blood flow in the brain. That ramps up the delivery of good things to brain cells, like oxygen, glucose and those amazing exerkines. And it helps remove more bad things, namely toxic proteins, like amyloid, that can build up and damage brain cells, increasing the risk for Alzheimer’s.

All of the changes brought on by exercise are “essentially allowing your brain to age more slowly than if you’re physically inactive,” said Kirk Erickson, the chair of neuroscience at the AdventHealth Research Institute.

The benefits are particularly pronounced in the hippocampus, a region critical for learning and memory. In older adults, the hippocampus shrinks 1 to 2 percent a year, and it is one of the main areas affected by Alzheimer’s. Researchers think physical activity helps to offset some of that loss.

The best exercise you can do for your brain is the one you’ll do consistently, so find something that you enjoy and that fits easily into your life.

Walking is one option; two neurologists I spoke to said they got their exercise in by walking at least part of the way to their offices. Recent research suggests that just a few thousand steps a day can reduce the risk of dementia. It’s important to get your heart rate up, though, so “walk as though you’re trying to get somewhere on time,” said Dr. Linda Selwa, a clinical professor of neurology at the University of Michigan Medical School.

Or you could try swimming, cycling, Pilates, weight lifting, yoga, pickleball, dancing, gardening — any type of physical exertion can be beneficial.

If the thought of working out feels like a drag, try pairing it with something else you enjoy doing, like listening to an audiobook. This is a trick that Katherine Milkman, a professor who studies habits at The Wharton School of the University of Pennsylvania, calls “temptation bundling.”

For Day 3, we’re asking you to spend at least 20 minutes exercising for your brain. Go for a walk with your accountability partner if they’re nearby. (If not, call them and do a walk-and-talk.) Or let us find you a new workout to try, using the tool below. As usual, we can all meet in the comments to catch up and check in.