How Does Exercise Benefit The Brain?


00:02 : Welcome to Better Brain Fitness, hosted by doctors Josh Turknett and Tommy Wood. In this podcast, we will explore the frontiers of how to keep our brain fit and healthy so that we can perform at our best and do the things we love for as long as possible. Let’s go. All right welcome to another episode of the Better Brain Fitness podcast. I am joined here today by my cohost, the ubiquitous doctor tommy Wood.

00:35 : Love, Tommy hello ubiquitous. That’s not an adjective i think it’s been applied to you before, but I like it. Well, yeah well, I mean, if anybody’s like in the in the world of health and fitness podcasts, they’re going to find that you’re pretty ubiquitous right? I appreciate it, anybody who’s listening across the range of podcasts. So, and Tommy is going to be fielding today’s question, which I think is in his wheeled house. And it comes from a listener, Michael in Greenville, virginia, who says how big of a part does exercise like running or weight lifting, play in brain fitness.

01:18 : So tell me what you got. Exercise, weight lifting, brain health fitness. Big question, big question, big fan. Obviously something that I’m very passionate about as the question is asked, it’s a good one and it’s something that we haven’t touched upon. In the same way with respect to the other things that we talked about, which is like can we put a number on how important physical activity is? And when we do things like this, people use something called population attributable risk or some version of that which basically says if we eliminated this as a risk factor, right so everybody did enough physical activity, did enough running and brisk walking and weightlifting, how much of the dementia burden would we reduce? And I don’t really think that we can answer the question in the way that people do that, right? Because first of all these factors don’t they aren’t these linear combinations of things.

02:28 : And what I mean is that you can’t just like stack the numbers on top of each other and say if we just remove this one at a time we can reduce this much of dementia risk because we also know they interact and with a bunch of things right if you have you fix a little bit of multiple risk factors, you can have an outsized effect to this. The several studies they haven’t really been applied in would say dementia risk directly but for things like mortality risk in those who have chronic sleep deprivation, that risk is offset if they’re very physically active, right so these things aren’t like single variables that we can look at in isolation.

03:09 : With that said, when people do look at population attributable risk, it kind of the numbers kind of vary there was a Lance at Commission report which looked at all the potential modifiable factors. I think they missed the bunch, but this came out a couple years ago. They put physical inactivity as like 2 % of all dementia risk. However, other things they looked at included hypertension, obesity, right other things that we know may be impacted by physical activity and there are other people who put the population attributable risk or some equivalent of that about 15 % so about 15, maybe up to 15 % of dementia is modifiable by improving physical activity.

03:56 : So I think it’s a good chunk definitely something that we should be tackling when then people might say well how much and what should I do. And there was a recent metaanalysis by Gallada Gomez Atal in Aging Research reviews came out last year where they basically took all the studies of various types of physical activity and did what we call a meta regression which is basically across multiple studies you can do this dose response curve of physical activity and cognitive function they were looking at. And what they found was that to see a clinically meaningful, not just statistically significant but clinically meaningful as in you can measure this improvement and it’s likely to have a significant benefit to your cognition and your quality of life.

04:46 : The dose is around 700 met minutes per week and the reason they did it that way, a met is a is a measure of how strenuous the activity is and what they see and what we see actually across a bunch of different health outcomes is that the effect of exercise is this product of intensity times time so if it’s less intense but you do more of it, that’s pretty much as good as doing something that’s more intense but for a short period of time.

05:15 : And so 700 minutes per week, if we break that down into activities per day, it’s probably like 60 minutes of light walking per day or 20 minutes of Pilates or you know, brisk walking or weightlifting per day or like 5 minutes of really intense sprinting per day like that’s what it looks like. And then they see, you know, the benefit increases up to about double that, right so maybe a couple of hours of walking or an hour of weightlifting or 10 or 15 minutes of sprinting per day, something like that. So and then after that you kind of see the, you know, more probably isn’t better.

05:57 : But if you think about all the ways you could kind of stack that up, you know, maybe you do an hour of walking in and around work and then you go to the gym for half an hour or you go to a dance class for an hour, right you’re right up at that sort of upper limit of benefit in something that I think most people are capable of doing. So what’s nice is that whatever you like to do is something that I think you should do and there’s this linear benefit up to something like, you know, an hour or two of physical activity per day, you know very much in line with government guidelines.

06:36 : And so the more you do above what you’re doing right now, you’re probably going to see some benefit. Hey there. So if you like this podcast, then I think you will enjoy the Brain Joe Connection newsletter. The Brain Joe Connection is a free newsletter sent out twice a month and is all about the science of how to keep our brain fit and healthy, along with products, books, tools and resources for improving brain health and function that we use and recommend.

07:04 : To subscribe. You can go to brainjo dot Academy forward slash Connection or click the link in the podcast description. All right now back to the show then. Beyond that people might ask well how do I break that up, you know is this you know because we asked about you know aerobic or endurance lab activities and weight lifting or strength training. And then I think we can go to some of the sort of the interventional randomized control trials in older individuals, people in their, you know generally they look at people in their sixties and seventies do some kind of exercise intervention and then look at you know cognitive or brain related outcomes.

07:51 : And one study that I talked about a lot is this classic study that was published in PNES in 2011 where they randomized people to 40 minutes, three times per week of brisk walking and they compared it to a stretching control group and in that intervention group 40 minutes of brisk walking and they actually did a ramp up so if people hadn’t done a bunch of walking before they sort of slowly built up the time and intensity over a few weeks and then they did this for a year and they saw in the brisk walkers an increase in the volume or size on an MRI scan of hippocampus which we know is an important part of the brain for memory and is sort of atrophies or decreases in size we lose some neurons there or some volume there in various types of dementia particularly Alzheimer’s disease and that seems to be reversed in this population i think they’re mostly in their sixties and seventies.

08:46 : So then you can think, all right, so you know day-to-day I should probably spend a good amount of time just any kind of walking. I think that’s always a good baseline. Something like 8000 steps per day is where you know it’s there’s a linear benefit up to something like 8000 steps per day and then it the benefit starts to tail off with more but obviously more could be, could be good if that fits into your lifestyle. So something like that. Then on top of that, three times per week, you know, 45 minutes to an hour of some kind of slightly more strenuous physical activity so in the study that did brisk walking, but we’ve talked previously about cognitive demand so maybe you get additional benefit if it’s dancing or it’s badminton or table tennis.

09:34 : And all of these have been studied in randomized control trials compared to something that’s similarly physically strenuous but doesn’t have the same cognitive component you’re not reacting to the environment, reacting to a ball or somebody else. And we see additional benefit from this coordination component and I think if we can combine the coordination component with this sort of lower end aerobic activity, something you could keep doing for an hour, that’s that optimal benefit and again you pick the thing that you like to do that has some kind of skill these are studies call it open skill movements because it has the physical activity component but then it also has this reaction or some other kind of motor coordination component.

10:21 : So three times per week, two or three times per week something like that on top of your just like general physical activity, you know a few thousand steps per day. Then we’ve seen from other interventional studies that you can, you can get improvements in cognitive function and the structure of the brain, particularly the white matter of the brain with resistance training. And in these studies then it’s something like again, two to three times per week, you go and you do 6 exercises. This should be like basic machines in the gym that cover the whole body like a leg press, a chest press, some kind of pull down. And you do that for three sets of something like 8 to 12 repetitions a couple of times per week and you can see significant benefit there.

11:09 : More broadly, if we’re looking at the minimum effective dose to improve strength and muscle mass in the general population, there was a nice sort of metaanalysis and scoping reviews by Evason at Allen and Sports Medicine in 2021 and they have a really nice sort of summary figure that shows this but essentially it’s four sets per muscle group per week, somewhere in the range of 6 to 15 reps and that’s not very much. You could probably do that in less than an hour per week, I think a little bit more than that like some of these other studies have done. So where if you’re doing three sets per muscle group, 2 times per week, so it’s more like six sets per muscle group, you know, and again, maybe just six exercises that’s that that’s a really good sort of sweet spot.

11:57 : And I think, you know, easily you could do that in sort of an hour or 90 minutes total per week you split it to two sessions of 45 minutes or something like that. So we have general physical activity we have some slightly more strenuous aerobic activity three times a week, ideally with some kind of coordination component. Then we have strength training twice per week. And then if you’ve got additional time above that time for one more sort of structured physical activity session, I would do something that’s more intense, some kind of interval training or sprinting or something like that we know that we do really intense exercise it releases a whole bunch of things like lactate, which are great for the brain, a bunch of signaling factors that seem too beneficial.

12:45 : But I think that’s kind of like the cherry on top if you do everything else, you’re in really good shape. But similarly, it can be whatever you like it could be you know you’re doing your brisk walk and you sort of Sprint whatever sprinting is for you know for a short period of time and then you rest for four or five times that period of time and it could be any anywhere between 15 seconds and two or three minutes nice long rest in between you do that two or three times something like that.

13:11 : And we know from other population studies that if you improve your cardiovascular fitness that’s associated with a decline in the rate of incidence of dementia. It was a bigger Scandinavian population study that showed this. So one way to figure out whether you are improving your cardiovascular fitness is to have some kind of like standardized test that you can do and then redo and see whether you’ve improved and you might do that every six months or something it’s not something you have to do a lot of the time.

13:48 : And if you aren’t very physically active, active to begin with, just your brisk walking is going to improve your cardiovascular fitness it’s going to be great if you’re already fairly physically active, but you want to improve your cardiovascular fitness a bit more than I think that, you know, having a session that’s a little bit more intense with those intervals, like I talked about is going to help more it sort of depends where your starting point is, but to figure out whether you are improving your cardiovascular fitness with some kind of hard metric, you know, people talk about something called V O2 Max, which is the maximum amount of oxygen your body can use during exercise.

14:22 : There are ways to measure it sort of formally. They’re not very fun and they’re expensive to do in the lab you get hooked up with a mask and you get thrown on a treadmill and tortured. You don’t need to do that. We know that your VO2 Max is related to basically how well you can perform in the sort of five to 10 minute window. So you can pick any exercise you like. It could be, again just brisk walking, could be on a bike, could be on a treadmill, could be on a row machine, assault bike, anything like that. And then you can see how far can you go in 5 minutes or 6 minutes.

14:57 : And just pick a number and then try it and just go as far as you can in 5 minutes or 6 minutes. And then in six months time try that again. And if you’re going further or you have a higher, you know if you’re measuring watts as an output, you’re doing more watts for that period of time, then we you know your VO2 Max is almost certainly improved and all you’re looking for is sort of improvement over time i don’t think the absolute number really matters that much, but that’s a nice way i think that people can just have a benchmark and then you know once or twice a year maybe see that they’re seeing some improvement so we’ll kind of go over that one last time.

15:33 : A good amount of just general activity moving around every day, not intense 8000 steps, something like that. Something a little bit more strenuous. I deal with a coordination component 3 times a week, two or three times a week, lifting weights again maybe half an hour 45 minutes twice a week. Then if you have some time do some kind of interval slightly more strenuous training on top of that. I think that’s you know that would be the perfect sort of brain focused physical activity schedule.

16:04 : But I would do it in that order probably so if if you only have time for one thing, do the badminton or the dancing or something like that if you have a bit more time, add the strength training, if you have a bit more time, add the high intensity stuff but anywhere you’re on that sort of scale and you add a little bit more, I think you’re going to see good benefit.

16:29 : That’s great man we’ll have to do more on this, on specific topics within this subject because there’s so many things, but that’s a really good overview. Can you talk just a little bit about from the theoretical side, what do we know about what’s happening in the brain what’s beneficial to the brain when you are exercising, whether that’s cardiovascular or resistance training? What one of the reasons why I think physical activity is so important is because there are so many things that happen when you exercise and pretty much every aspect of the things related to the brain you know when I’m studying actual brain injuries in way that we treat brain injuries as well.

17:11 : The things that work tend to be the things that work on multiple pathways in multiple ways at the same time. Which is one of the reasons that you know, I know that we agree that single focused drugs that target 1 molecule or one mechanism don’t really work it’s probably because these things are so multifactorial, but we can kind of lump it up into some different segments. So one aspect, and this is relevant to particularly the sort of coordination component activities as well as maybe resistance training or weightlifting is a direct neuromuscular stimulus.

17:50 : You are stimulating these connections from the brain to the body by asking it to do these sort of novel or challenging movements, recruiting more muscles, you know, working your motor skills, your coordination skills. I think so i think there’s a direct stimulus effects like we’ve talked about several times before then you’re maybe more related to the endurance type activities or aerobic activities like brisk walking but also you know some people have suggested that you know even a good weightlifting session gets your heart rate up.

18:23 : So it it’s relevant to that as well is your improving cardiovascular function. When you improve cardiovascular function, you’re improving the health of your blood vessels and those include the vessels to and inside the brain. And we know that if you want to support the function of the brain you need to get oxygen and nutrients to those areas of the brain and to do that you need healthy functioning blood vessels and one of the things that we see that’s the component of dementia is vascular disease you know the these blood vessels become diseased or they don’t respond to increase increased activity in the brain to supply more oxygen and nutrients as you would need it to normally.

19:05 : So supporting cardiovascular function I think is really is really important and it you know it also lowers blood pressure and these other things that are that are risk factors in that arena for dementia and decline. And then there were a whole bunch of things that are released by the muscle tissue when we exercise. And this is still an area that’s actively being researched i think you know every few months I see a fancy paper and a fancy journal that says hey we discovered this whole new molecule that does these amazing things when we exercise. And that’s one of the reasons why, you know, I really sort of enjoy or you know very much the support of physical activity for the brain is because there’s so many things that it does and we’re still we’re still learning about it and that’s exciting for me as a scientist but I already mentioned lactate, that’s a really important molecule for the brain, both in terms of being a metabolite, you use it for energy, but it’s also signals, a bunch of stuff and then you release things like brain derived neurotrophic factor which is this.

20:07 : Like it says, it’s a trophic factor which means it supports the growth and functions of neurons in the brain. We know that physical activity also down regulates systemic inflammation which is a risk factor for dementia and a bunch and as well as cardiovascular disease and other chronic diseases. So you’re sort of dampening that down, you’re improving immune function. So all of these things I think, come together. That’s one of the reasons why physical activity is such a powerful modulator of long term health. Yeah so clearly many different plausible mechanisms that we can point to by which these effects would occur.

20:48 : Yeah, just a couple of points to conclude with, as you mentioned, one of the limitations of this of doing sort of broad studies on this is it’s such a big category, right so there’s a, you know, there’s a huge difference in the types of different, you know, physical activities so lumping them under one umbrella is challenging and as you mentioned, there’s likely from the brain perspective some meaningful differences between, you know, going for a run versus playing a skill sport, right or dancing or something that involves coordinative movements that are going to be sort of very taxing to large parts of the brain in a way that’s something that you can perform while you’re son of just Adrian and it’s still going to be a totally different thing, not that it’s not beneficial, but not beneficial in the same way from the from the brain standpoint.

21:31 : So I agree that if you focus on any one thing, you know choose something that kind of lumps all of these things together, one of the things that’s gone, gone nuts recently is pickleball and I mean it’s and I think that’s fantastic you know it’s like it’s a has the all the you know, coordinative elements, it’s a great cardiovascular workout. It’s very social, you know it just organizes all these things into one so picking something like that I think is a great place to start it’s also much easier to get into a routine if it’s with other people like that.

22:04 : I didn’t I didn’t mention yoga or similar things like that you know Tai Chi has been, has been studied fairly extensively in this kind of area as well and those don’t necessarily have a social component but obviously would be probably better with friends if you do it yeah. But classes and so forth. Yeah exactly. But if you think about yoga there’s obviously a muscle strength component. You know it’s often you know physically challenging up to this sort of the low level aerobic sort of level and then all the coordination components. One thing is that obviously yoga just mainly affects muscles in the front of the body but not in the back of the body just based on how you can actually structure the resistance so if you’re doing a bunch of yoga, then it can also be useful to do some kind of strength training for the posterior chain like you know, deadlifts or pull ups or some of that so you’re working the back and the back of the legs as well.

22:59 : But you know it ticks a bunch of boxes in that area and I agree you get the most bang for your buck if you do something that covers multiple things at the same time, right. And then the last thing was that this kind of gets back to sort of our kind of fundamental thesis about building capacity into the system we talked about it with respect to cognition, but it also applies to our cardiovascular musculoskeletal system and I think it you want to think about all those systems in trying to build in excess capacity, which is really what’s going to translate into improvements in health and reduced risk of chronic disease and in all of the categories not just for the brain yeah and the more capacity of in the system, right, the longer it is before you know, you’re unable to do the activities of daily living and those are the things that you need in order to, you know, get social interaction in order to get cognitive stimulus so the more capacity you have, right, the longer you’ll be able to keep providing these inputs and doing these things that we know are supportive of health so you have multiple reasons to try and try and improve strengthen and fitness in various ways as much as you can all right, Absolutely.

24:08 : All right well, thank you, Michael and others who asked questions about exercise and if you have any followups on this topic that you would like to ask us or anything else on the topic of brain health and fitness, you can do so at All right, That is it for this episode we will see you next time thanks, Tommy.