Exercise changes the structure of your brain

What good is a walk for my brain?
20 November 2020

Interview with 

Áine Kelly, Trinity College Dublin


Walking on a trail


Let’s limber up and jump into how exercise can actually change the structure of the brain! Áine Kelly is a physiology professor at Trinity College Dublin, who’s particularly interested in exercise in relation to how the function of the brain changes with age, as she told Katie Haylor...

Aine - Being active, taking exercise, reduces in the long term your risk of development of for example, Alzheimer's disease. And what I'm interested in is understanding how exactly that happens.

Katie - I have been sitting for most of the day. So I think as we're talking about exercise, I'm going to have to stand up a little bit, move my chair away. And I want you to challenge me to do a couple of squats.

Aine - Okay. Well, squat away. Absolutely!

Katie - Not sure about my technique here, but I'll give it a go. I'I'm holding the microphone as well...

Aine - Yeah. Make sure your knees don't come too far over your toes or you'll be in the wrong position. Try to keep your back straight. Keep going....

Katie - How many do I have to do?

Aine - I would say to do 10 and then stop. Just get the blood moving.

Katie - Oh, I'm feeling warm already. I'm on seven. I'm wearing a wooly jumper, that wasn't very wise.... 10!

Aine - All your synpases should be firing now at this stage.

Katie - I've got my blood flowing [panting]. Um, it's pretty obvious that doing exercises like that over a longer period of time is good for my body. But scientists like yourself reckon this is actually good for my brain too. So perhaps you can tell us a bit about why exercise is good for the brain.

Aine - I mean, exercise is so important to general good health and good health of all of our organs. But there are several things additionally that it can do specifically for the brain that have an impact then on brain function in the long term. One of them is a process called neurogenesis, literally the birth and development of new neurons. It was thought for a long time that this didn't happen in the adult brain. That once we reached the age of full development that we couldn't develop any new neurons. And when the reports first came out about maybe 40 years ago or more that perhaps new cells could be developed in the brain, it was sort of dismissed because the dogma was that it just didn't happen. Now we have really good evidence that in fact, the adult brain does consistently produce new neurons throughout life.

So effectively you have stem cells in particular regions of the brain and given the correct stimulation, they are going to make more of themselves. And they're going to develop and they're going to develop into mature neurons. That process only happens in a couple of discrete regions in the brain. And one of them is the hippocampus, which is very important for learning and memory. And it turns out that probably the best stimulus for neurogenesis in the brain is physical activity. So exercising directly results in the production of these new neurons within the brain, in regions that are important for learning and memory. And this perhaps then is the link between exercise and preservation of brain function, particularly memory throughout life.

Katie - Is there a link here with mental wellbeing? I guess I'm specifically thinking about things like stress and depression, because it's sort of commonly understood that exercising regularly is a pretty good idea for your mood.

Aine - Absolutely. So again, on a couple of fronts. And there could be a potential neurogenesis link here as well, because certainly in animal models antidepressants can stimulate the same kinds of molecular and cellular changes that exercise can in particular regions of the brain. And neurogenesis it's being analysed in the context of, you know, diseases and disorders of the brain, Alzheimer's disease, Parkinson's disease, multiple Sclerosis, and indeed things like depression. So really it could, I suppose be a therapeutic target, so exercise itself in terms of taking more exercise as a preventative measure, or even as sort of an adjunct therapy for some of these things. But also if scientists like myself can understand the cellular, the fundamental biological basis of how exercise is doing this, then that might be a target for example, for drug therapies, for people maybe who can't exercise because of disability or, you know, fragility, there might be some kind of pharmacotherapy or a drug therapy that could mimic the effects of exercise on the brain. I mean, that, that's very aspirational and it's in the long-term! But it's a possibility

Katie - You wrote a recent article in The Conversation about the benefits of exercise for the brain in terms of actually changing brain structures. Can you take us through that? 'Cause you mentioned memory, which you've just mentioned briefly, and then I think you mentioned blood vessels and also inflammation. Maybe we can start , with memory and learning.

Aine - Yep. So again, this is all very much linked to some of the things that I've been talking about. And particularly that this hippocampus region of the brain, that's an important in memory. A number of studies have used MRI scans to sort of visualise the brain and look at the structure of the brain and that the volume of the brain. And we know that some literal shrinkage of the brain can happen with age and that can be accelerated very much in things like Alzheimer's disease. So some studies have shown that taking regular physical activity, sort of a prescribed exercise programme, can actually reverse some of that age related shrinkage of these particular brain regions, for example. And again, that might very well be linked to this whole area of neurogenesis or being able to develop new neurons. On the large scale when we just think of the whole volume of the brain or indeed of particular brain regions, and that's a structural change.

One of the other things that we know happens with exercise is that it can stimulate the production of new blood vessels. This is something called angiogenesis. This happens in your muscles. Okay. If you work out and try to sort of, you know, bulk up your muscles and increase the size of your muscles, you're going to have some growth of new blood vessels along with that, to support the new muscle tissue. Pretty much the same or a similar kind of thing can happen in the brain because we know that with exercise, new blood vessels develop in the areas where neurogenesis is taking place. So the blood vessel development and the development of new neurons are happening hand in hand. And this means that those newly born neurons will get the blood supply that they need to survive and to function properly.

Katie - What about inflammation? Because it seems more and more that inflammation is being implicated in quite a lot of disease.

Aine - Absolutely. The immune system is fascinating because it's so complicated and is consists of so many different cells and different areas of the body that can secrete different molecules. When we think about physical activity and exercise, we have to think of the flip side of that, which is being sedentary. And not being active is the source of lots of problems in the body. And particularly at the moment when a lot of us are kind of confined a bit more to our houses and we're not moving around as much as we normally do, but when you are sedentary, that increases the risk of obesity, type two diabetes, certain forms of cancer for example. That again is linked to the immune system because it creates - sedentary behaviour and bad diet and so on - creates a sort of an inflammatory environment within our tissues. That inflammation is linked to some of these conditions. And when we think of the brain, it's linked to age-related neurodegeneration, Alzheimer's disease and so on.

But the good news is that moving counteracts that. Exercise has quite a powerful anti inflammatory property. So it can counteract these sort of pro-inflammatory events or pro-inflammatory changes that happen due to sedentary behaviour and other things. So it can kind of modulate the function of the immune system towards a sort of an anti-inflammatory type of approach. And when we think about what that might mean for the brain, we know a lot more now about neuroinflammation, inflammation in the brain, and how that's linked to age or degeneration or Alzheimer's and so on. And we know some of the cell types that are involved as well. And we know quite a bit about the biology of those cells and how they act. Exercise is able to change the function of those cells away from being very chronically pro-inflammatory and damaging, to sort of switch off that kind of inflammatory activity of those cells. We can have inflammation in the brain. We do have inflammation in the brain. But it seems that exercise is able to counteract that. And that again is another mechanism by which exercise is helpful and protective for the brain.

Katie - When you talk about exercising for the benefit of the brain, has there been research done to indicate how regularly you need to exercise for there to be a benefit?

Aine - We don't have specific guidelines for the brain. What it appears is if we meet those recommended physical activity guidelines - for adults that 150 minutes of sort of moderate intensity exercise per week or 75 minutes of vigorous activity. And then we need to do things that will build strength and flexibility as well. Just for general health. That's for adults. For children it's an hour per day. We know that children in particular school children are not meeting the physical activity guidelines, which is a major worry for things like cardiovascular health and metabolic health, but also potentially for brain health, because some of the studies that are coming through, at least in animal models, it seems that early life exercise, and this is something that I'm interested in working on myself, even if you are sedentary later in life, still has protective benefits. So we really need to be active, particularly when we are younger to sort of, I suppose, build up some of that benefit. I think consistency is the thing. So being consistently active over long periods of time, but in terms of maybe it should be 200 minutes a week specifically for the brain. We don't have that level of detail because the science is still in question at the moment. I think, you know, the best advice is to follow the general guidelines for good health and just to move as much as you possibly can.


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