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Sedentary, older adults who took aerobic dance classes twice a week showed improvements in brain areas critical for memory and thinking.
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By Gretchen Reynolds
March 3, 2021
Exercise can change how crucial portions of our brain communicate as we age, improving aspects of thinking and remembering, according to a fascinating new study of aging brains and aerobic workouts. The study, which involved older African-Americans, finds that unconnected portions of the brain’s memory center start interacting in complex and healthier new ways after regular exercise, sharpening memory function.

The findings expand our understanding of how moving molds thinking and also underscore the importance of staying active, whatever our age.

The idea that physical activity improves brain health is well established by now. Experiments involving animals and peopleshow exercise increases neurons in the hippocampus, which is essential for memory creation and storage, while also improving thinking skills. In older people, regular physical activity helps slow the usual loss of brain volume, which may help to prevent age-related memory loss and possibly lower the risk of dementia.

There have been hints, too, that exercise can alter how far-flung parts of the brain talk among themselves. In a 2016 M.R.I. study,for instance, researchers found that disparate parts of the brain light up at the same time among collegiate runners but less so among sedentary students. This paired brain activity is believed to be a form of communication, allowing parts of the brain to work together and improve thinking skills, despite not sharing a physical connection. In the runners, the synchronized portions related to attention, decision making and working memory, suggesting that running and fitness might have contributed to keener minds.
 
But those students were young and healthy, facing scant imminent threat of memory loss. Little was known yet about whether and how exercise might alter the communications systems of creakier, older brains and what effects, if any, the rewiring would have on thinking.
  
So, for the new study, which was published in January in Neurobiology of Learning and Memory, Mark Gluck, a professor of neuroscience at Rutgers University in Newark, N.J., and his colleagues decided to see what happened inside the brains and minds of much older people if they began to work out.

In particular, he wondered about their medial temporal lobes. This portion of the brain contains the hippocampus and is the core of our memory center. Unfortunately, its inner workings often begin to sputter with age, leading to declines in thinking and memory. But Dr. Gluck suspected that exercise might alter that trajectory.

Helpfully, as the director of the Aging & Brain Health Alliance at Rutgers, he already was leading an ongoing exercise experiment. Working with local churches and community centers, he and his collaborators previously had recruited sedentary, older African-American men and women from the Newark area. The volunteers, most of them in their 60s, visited Dr. Gluck’s lab for checks of their health and fitness, along with cognitive testing. A few also agreed to have their brain activity scanned.

Some then started working out, while others opted to be a sedentary control group. All shared similar fitness and memory function at the start. The exercise group attended hourlong aerobic dance classes twice a week at a church or community center for 20 weeks.

Now, Dr. Gluck and his research associate Neha Sinha, along with other colleagues, invited 34 of those volunteers who had completed an earlier brain scan to return for another. Seventeen of them had been exercising in the meantime; the rest had not. The groups also repeated the cognitive tests.

Then the scientists started comparing and quickly noticed subtle differences in how the exercisers’ brains operated. Their scans showed more-synchronized activity throughout their medial temporal lobes than among the sedentary group, and this activity was more dynamic. Portions of the exercisers’ lobes would light up together and then, within seconds, realign and light up with other sections of the lobe. Such promiscuous synchronizing indicates a kind of youthful flexibility in the brain, Dr. Gluck says, as if the circuits were smoothly trading dance partners at a ball. The exercisers’ brains would “flexibly rearrange their connections,” he says, in a way that the sedentary group’s brains could not.

Just as important, those changes played out in people’s thinking and memories. The exercisers performed better than before on a test of their ability to learn and retain information and apply it logically in new situations. This kind of agile thinking involves the medial temporal lobe, Dr. Gluck says, and tends to decline with age. But the older exercisers scored higher than at the start, and those whose brains displayed the most new interconnections now outperformed the rest.
This study involved older African-Americans, though, a group that is underrepresented in health research but may not be representative of all aging people. Still, even with that caveat, “it seems that neural flexibility” gained by exercising a few times a week “leads directly to memory flexibility,” Dr. Gluck says.

It's not enough to build muscle and achieve aerobic fitness. You need to think about flexibility, too. Stretching can help.
You may think of stretching as something performed only by runners or gymnasts. But we all need to stretch in order to protect our mobility and independence. "A lot of people don't understand that stretching has to happen on a regular basis. It should be daily," says David Nolan, a physical therapist at Harvard-affiliated Massachusetts General Hospital.
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Why stretching is important
Stretching keeps the muscles flexible, strong, and healthy, and we need that flexibility to maintain a range of motion in the joints. Without it, the muscles shorten and become tight. Then, when you call on the muscles for activity, they are weak and unable to extend all the way. That puts you at risk for joint pain, strains, and muscle damage.
For example, sitting in a chair all day results in tight hamstrings in the back of the thigh. That can make it harder to extend your leg or straighten your knee all the way, which inhibits walking. Likewise, when tight muscles are suddenly called on for a strenuous activity that stretches them, such as playing tennis, they may become damaged from suddenly being stretched. Injured muscles may not be strong enough to support the joints, which can lead to joint injury.
Regular stretching keeps muscles long, lean, and flexible, and this means that exertion "won't put too much force on the muscle itself," says Nolan. Healthy muscles also help a person with balance problems to avoid falls.

Where to start
With a body full of muscles, the idea of daily stretching may seem overwhelming. But Nolan says you don't have to stretch every muscle you have. "The areas critical for mobility are in your lower extremities: your calves, your hamstrings, your hip flexors in the pelvis and quadriceps in the front of the thigh." Stretching your shoulders, neck, and lower back is also beneficial. Aim for a program of daily stretches or at least three or four times per week.
Find a physical therapist (your local Y is a good place to start) who can assess your muscle strength and tailor a stretching program to fit your needs. If you have chronic conditions such as Parkinson's disease or arthritis, you'll want to clear a new stretching regimen with your doctor before you start.

The cumulative effect of stretching
​Stretching once today won't magically give you perfect flexibility. You'll need to do it over time and remain committed to the process. "It may have taken you many months to get tight muscles, so you're not going to be perfectly flexible after one or two sessions," says physical therapist David Nolan of Massachusetts General Hospital. "It takes weeks to months to get flexible, and you'll have to continue working on it to maintain it."
A hamstring stretch will keep the muscles in the back of your thigh flexible. Sit on the floor with your legs in front of you. Slide your hands down your legs until you feel a burning sensation. Hold for 30 seconds, then slowly return to a sitting position.

Proper execution
We used to believe that stretching was necessary to warm up the muscles and prepare them for activity. However, mounting research has shown that stretching the muscles before they're warmed up can actually hurt them. "When everything is cold, the fibers aren't prepared and may be damaged. If you exercise first, you'll get blood flow to the area, and that makes the tissue more pliable and amenable to change," says Nolan. All it takes to warm up the muscles before stretching is five to 10 minutes of light activity, such as a quick walk. You can also stretch after an aerobic or weight-training workout.
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Hold a stretch for 30 seconds. Don't bounce, which can cause injury. You'll feel tension during a stretch, but you should not feel pain. If you do, there may be an injury or damage in the tissue. Stop stretching that muscle and talk to your doctor.
 
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