For the last decade, Mark Gluck has been running brain health education programs at churches and senior centers in the Newark, N.J., area. Often, they focus on how exercise and memory are linked.

He likes the people and the work. It is not only his passion, but also his profession. He is a Rutgers professor of neuroscience and public health and director of the Aging and Brain Health Alliance at Rutgers University-Newark.

Recently, by studying some of the same seniors he had been working with, his team unlocked a few more secrets about how exercise helps the aging brain and why. We asked this avid cyclist and Penn Valley native about it.

It’s been well-established that exercise improves brain health. What was missing that you were trying to learn?

Yes, we do know that exercise is good for our brain. It helps our memory and our alertness. But what is actually changing in the brain?

And why is it that when some people exercise, it makes their mind super sharp and super bright, and really helps the brain, but when other people do a lot of exercise, it doesn’t help their brain so much? Exercise may help their heart. It may help other aspects of health. But there seems to be lots of individual variation in how much different people’s memory and brain function benefits from exercise.

What we are focusing on is this: What is it that predicts who will be resilient and maintain their brain health over the long term? For that reason, we don’t study people with Alzheimer’s disease. Rather, we look at people who are exceptional super-agers, people who are doing fabulously in their 80s, 90s, or beyond. We are recruiting people who at that age are sharper than the average 50-year-old. From studying them, we want to find out how to help everyone else maintain similar optimal brain health. As such, our focus is the pathways to healthy aging.

How did you set up the study?

We held exercise classes in churches and senior centers in the greater Newark area. People would come in twice a week, for an hour each time. They did cardio-fitness dance exercise — sort of like Zumba, but with a broader range of music, including Motown and R&B. It was fun. It was social. They did this for 20 weeks — five months. We had a comparison group that did not exercise.

Before and afterward, we evaluated their cognition, and, with MRIs, their brain activity. An MRI gives you an indirect measure of which parts of the brain are most active at any given point in time.

As part of our study of Pathways to Healthy Aging in African Americans, we worked specifically with African Americans. African Americans have traditionally been underrepresented in biomedical research. And that’s a problem, particularly for research into aging and Alzheimer’s disease because African Americans have two to three times the rate of Alzheimer’s, compared to Caucasians. A lot of the reason behind this health disparity is probably health and lifestyle factors, including exercise.

What did you learn?

Our study showed that what’s being changed by exercise, particularly cardiovascular exercise like our cardio-dance classes, is how flexible the different parts of the memory circuits become. Here’s an analogy: If you go to a cocktail party and you talk to the same two people for the entire evening, you’re locked into a rigid conversation. But if you go to another party where you engage in different conversations with different people, that party has a much more dynamic flavor and the people are much more flexible about who they’re talking to and what they’re talking about.

That’s the kind of flexibility that we see in the brains of people who exercise and are physically fit. The different parts of the memory circuit are like the guests at the livelier party. They are talking to each other.

The second finding involved a particular gene called ABCA7. In people with one variant of the gene, no matter how physically fit they became, their brains didn’t get any more flexible and their memory systems didn’t function any better.

People always ask, is it genes, or is it environment and behavior? Almost always, however, the answer is that there’s an interaction between genetics, behavior and environment. To have the most protection for the brain, the most flexibility, you not only need to be physically active, but you also have to have the right genes that allow you to take advantage of the exercise to improve brain health.

The other aspect that’s unique is that these genes may function differently in different racial groups, which is why it is so important to enroll more African Americans in studies of exercise and brain health.

Why is brain flexibility good?

When people think about improving their memory, they often think about remembering something later, exactly as it occurred. That’s certainly important for things like phone numbers.

But in life, we rarely see exactly the same situation twice. Rather, what we need to do is take what we’ve experienced in the past and apply it and generalize it to things that are novel but similar. That’s how we get about in the world because the world is always changing and we need to be able to flexibly apply our past experiences to the unexpected novel challenges ahead.

We see this kind of flexibility at a behavioral level. Let’s say you hate broccoli. If you just avoid broccoli, that would be very rigid. But if you take what you’ve learned about broccoli and apply it to cauliflower, you have flexibly applied your learning from one stimulus to something similar.

If you think about someone who’s getting old, and beginning to get dementia, a certain amount of what you see isn’t just that they forget things. In addition, they become mentally rigid. They know how to do things a certain way and if something is disrupted or something is different, their ability to cope breaks down. They may know the route to the hairdresser — left, right, left — but if the road is blocked and they need to find a different route, they may not be able to. As dementia begins to set in, and the brain loses flexibility, people lose the ability to flexibly adapt and come up with alternative solutions.

This all involves the hippocampus, the gateway to memory. The hippocampus is not where memories are stored in the long term, but it’s where they first go to be organized and sorted and figured out as far as what’s important and what’s not and what’s similar to what. The more alive and vibrant and flexible the brain is, the better it can do this job.

How much exercise do we need to gain these benefits, assuming our genes cooperate?

What’s really critical is getting that heart rate going. If there are two people at the gym on exercise cycles and they’re chatting away while they’re exercising, they’re not in the zone they need to be in. You should be in a zone where your heart is pumping so fast you can’t hold a sustained conversation.

There’s a lot of evidence to suggest that getting into that more intense heart rate is triggering all sorts of really important things in the brain. It’s also probably triggering the growth of new neurons in the brain, including in the hippocampus.

My study subjects exercised for just two hours a week. The general recommendations for exercise are to try to get 150 minutes of exercise a week. We’re going to be starting up again post-pandemic with another set of studies where we’ll increase that to three times a week.

In the future, we want to look a lot more at the genetics. And now that we’ve learned about cardiovascular exercise, we want to see if there are different brain benefits to stretching, toning and strengthening.

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