Older adults who are physically fit have better memory and executive function—which includes skills like problem-solving, planning, and organization—than adults who are out of shape, according to research from Boston University.

The study, published in the Journal of Gerontology last December, compared brain power among 33 young adults aged 18 to 31 and 27 older adults aged 55 to 82 with a wide range of fitness levels. In the younger participants, better heart and lung fitness had no effect on memory or executive function, but for older adults it translated to improved memory, problem-solving, and decision-making skills.

Brain Benefits

These findings echo those of many other studies that establish a connection between aerobic fitness and brain fitness, says Sandra Bond Chapman, PhD, founder and chief director of the Center for BrainHealth at the University of Texas at Dallas.

In a study published in the journal Frontiers in Aging Neuroscience in November 2013, Dr. Chapman's group found that older adults who did one hour of aerobic exercise at least three times per week had increased blood flow to key areas of the brain, including the hippocampus—the primary region affected by Alzheimer's disease—and the anterior cingulate, which has been linked to improved mental function in late life.

The 37 participants underwent brain scans after six weeks of regular exercise, and again after 12 weeks. "We started seeing some changes at the six-week period," Dr. Chapman says. "Other studies have suggested it might take six months to a year of regular aerobic exercise to get these results; in our study, this boost in blood flow to key areas of the brain came earlier."

Memory Boost

"We found that people who were assigned one hour of aerobic exercise three times per week for three months significantly improved both their immediate memory and their delayed memory," says Dr. Chapman. Immediate memory is the ability to recall a phone number you've just heard long enough to dial it, while delayed memory is the ability to remember it 20 minutes later, she explains. "We know one of the earliest symptoms of Alzheimer's disease is impairment in delayed memory."

More Than a Stroll

While any exercise is better than no exercise at all, Dr. Chapman says that for significant brain benefit, exercise must be vigorous—increasing your heart rate and your breathing—and sustained; more than half an hour at a time is best. That means a gentle stroll in the park, while certainly good for you, probably isn't boosting your brain function. And, of course, if you go back to being a couch potato, your brain probably will, too. "Our body wasn't made to sit," Dr. Chapman says. "It was made to move!"

Get Physical

Exercise is good for everyone, but it's especially beneficial for those with neurologic conditions. Studies show it can help improve mobility, make daily tasks easier, and sharpen brain function. Here's how to get started.

1. TALK TO YOUR DOCTOR. Your neurologist or primary care physician may be able to recommend safe and effective types of exercise for someone with your condition.
2. GET YOUR HEART PUMPING. Choose an activity that increases your heart rate, such as swimming, cycling, working out on an elliptical trainer, or dancing.
3. CONSIDER PHYSICAL THERAPY. Look for someone with experience in training people with your particular condition.
4. START SLOW. If you have a fatiguing condition like multiple sclerosis, pushing yourself too hard too soon can set you back. Begin with shorter bouts of exercise lasting 10 or 20 minutes. Ideally, you should work up to a total of at least 150 minutes of aerobic exercise per week.