Can You Walk Too Much?


[00:00:00] Okay, welcome to another episode of the Better Brain Fitness. podcast. Today I’m joined again by my ambulatory co host, Dr. Tommy Wood. Hello, Tommy. Hello. So today, Tommy is going to be fielding the question, which comes from Steve in Cleveland, Ohio. Steve asks, if some walking and exercise is good for your brain, is there a point where it can be detrimental to brain health?

So, good question. We’ve heard a lot. about the benefits of walking and different things at different times in terms of like how much is good for you. So I guess there’s the question of how much is enough, but also on the flip side, is there a point where it’s too much? And is there a point where also where the benefits kind of start to diminish or go away?

So curious to hear what you have to say about this one, Tommy. Yeah, it’s a great question. And I’ll admit that [00:01:00] whenever I talk about the benefits of physical activity, Usually, I’m talking about linear positive benefits, because for the vast majority of people out in the world, they could move more, and if they move more, they will see more benefit.

And most studies and meta analyses, meta regressions suggest that that benefit is approximately linear, which just means that the more you do, the more benefit you get, and this, like, in a continuous manner. And that could be weight training, it could be walking. Several, you know, dancing, several other forms of physical activity.

However, whenever I say that, there’s always somebody that says, yes, yes, but there’s a point where, you know, there’s either diminishing returns, then it can become you know, actively harmful. And of course, that is true. Overtraining is a thing. And depending on how you think about it, often people think that it may be just due to under recovery, right?

You’re not eating enough energy, you’re not getting enough sleep in order to [00:02:00] recover from that physical activity, regardless of the exact mechanisms. Of course, there is a point where there are diminishing returns and then perhaps some, some potential for, for detrimental effects. And I would think about that in, in three…

broad areas. So it’d be based on the actual stress of exercise on caloric or energy availability. And then there’s also an association with mental health that we’ll talk about. But first, I’ll, I’ll maybe just address the first bit of your question, which you kind of added in, you know, the dose. And we’ve talked about this briefly before, but there was a or maybe extensively before.

Because usually I’ll start talking about exercise when I get started. So there’s a recent meta analysis. This is a nice one by Gerardo Gomez Atal in Aging Research Reviews in 2022. We’ll link to it. And there’s this sort of main figure where they did this meta regression, right? So it kind of looks, looks at the dose response of physical activity on cognitive function.

And they found that the minimum effective dose to see a [00:03:00] meaningful improvement in cognitive function was they, they classify it in met minutes per week. So it’s basically a time times and intensity. And it’s essentially about, general physical activity guidelines, 150 minutes a week of moderate to vigorous physical activity, kind of like standard government guidelines.

That seems to be the minimum, minimum effective dose, which is nice. You know, I like that. I think that’s something that’s achievable for everybody. They do show that, you know, up to at least double that, you get an increasing benefit, right? So now we’re talking five hours a week of moderate to vigorous physical activity, you know, something like 45 minutes to an hour a day.

There seems to be more benefits the more you do. Beyond that when you look at the graph, the confidence intervals get kind of wide because just not that many people do that much exercise. So it’s, it’s hard to really extrapolate beyond that point, but it, it kind of looks like we expect to see increasing benefits up to like, you know, an [00:04:00] hour or so a day of, of moderate to vigorous physical activity.

So like brisk walking up to, you know, weightlifting, maybe running, you know, all those kinds of activities. So then to kind of take it further, I think we need to delve into the research related to athletes because those are, those are the types of groups where they’re, they’re probably gonna be training much more than that, you know, maybe training several hours a day, 20, 30 hours a week, certainly possible.

I did, I did that in the past when I was a a rower in college. And so, where we look there, there is certainly some evidence to suggest that overtraining or overreaching, so studies where they take individuals and they say, what’s your baseline level of training, and they double it for a period of week, so you kind of like double the volume immediately, that’s what, for a short period of time, we call that, say, an overreaching protocol, or if you do that for an extended period of time, you might call it overtraining.

And then you start to see… Decreases in some measures of reaction time and [00:05:00] executive function. So doing things like the Stroop test. So, so if you immediately and dramatically increase somebody’s training volume in somebody who’s already training a lot, you do see seem to see some decrease in cognitive function.

If we extend beyond that, so very long periods of time where you have where you’re not eating enough food, essentially and that can come with overtraining just because you’re, you’re generating such a caloric debt that you physically cannot eat enough, or you’re restricting your energy intake for, for a related reason.

Then you might develop something that we call relative energy deficiency in sport, or RED S, and this used to be called the female athlete triad where female athletes who under eight then they become amenorrheic or they have issues with their cycle, they start to develop issues with their bone health and function.

But it’s been recognized in the last few years that this can also happen to males or You know, any [00:06:00] athlete. So, Red S when they look at across a range of studies in those who do have relative energy deficiency, and again, could be over training, could be under eating, could be both, there do seem to be decreases in cognitive function broadly as well as increases in the risk of depression and anxiety.

So multiple aspects of cognitive function may be impaired if this goes on long term. It made me think of The paper with the Bolivian Chimney, we talked about a few episodes back, where they looked at energy availability and brain volume in a variety of populations. And there’s essentially this sweet spot, which is that your brain volume and structure is positively correlated with the amount of energy availability, so how much food you’re eating, as long as you don’t tip over into excess energy intake.

So you basically want to have as much energy available for the brain without, you know, over, without overeating. So that’s, that’s [00:07:00] the sweet spot. And so if you’re restricting energy availability or you don’t have enough energy available because you just can’t get enough calories in because of the training volume you’re doing, that’s then going, you’re going to, you’re going to put yourself on a lower you know, lower point of that curve, and that may be one of the reasons why cognitive function gets affected.

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Another part of it can be that exercise is a stress. You know, we [00:08:00] activate the autonomics in the nervous system, we release cortisol, adrenaline, you know, all these things which if it’s extended and extensive. Right, and we don’t get an opportunity to rest and recover because of that, you know, exercise is a hormetic stressor, which means that it’s a beneficial stress, but only if we have time to adapt and respond to it.

So that could be, that could be part of that, as we’re activating some of these stress and inflammatory pathways, and if we don’t get a chance to recover adequately, that can negatively impact the brain. And we know that. yoU know, chronic activation of the sympathetic nervous system, chronic cortisol, you know, cortisol elevation of cortisol, all those things could negatively impact the brain.

So that can be another part of it. And then the final part could be reverse causality. So is somebody using large volumes of exercise in order to say, not deal with other issues? So sometimes disordered eating can be expressed in [00:09:00] terms of. Over over exercise or an exercise addiction. So it could also be the other way around, right?

There is some broader issue that’s that’s being expressed in large volumes of exercise. So that’s something that is worth considering as well. And certainly I’ve worked with a number of athletes with mental health issues, and that’s You know, one of the ways that those issues are expressed is in very high volumes of exercise, which, you know, often isn’t is not adequately adapted or recovered from.

And some of these things could be rooted in trauma and other things that may negatively affect the brain. And then exercise is just a symptom rather than, of course, or maybe a bit of both. So it’s certainly possible that very high volumes of exercise can affect can negatively affect the brain. It’s probably going to be due to other stresses in our life.

How well are we able to adapt and eat to recover and sleep to recover from that exercise. And if we go beyond our ability to adapt, rest and recover, that may then negatively impact the [00:10:00] brain for those reasons. So but I don’t think this is an issue for most people, but certainly if you’re training several hours a day you really have to work hard to recover adequately so that your, your brain is supported as best as possible.

Any thoughts or questions based on that? Yeah. One, one thing that just. As you were talking, this is something I’ve been thinking about recently, is that, and you bring this up in your answer, is that a lot of the issues that we see in health can be sort of conceptualized as problems of mismatch in terms of where the supply is mismatched to demand, and that can occur In either side, whether or not we sort of are overstimulating and we don’t have enough resources to match that stimulation or we have too many resources to match the level of stimulation more than we need for that level of stimulation and you know, that boils down to all the way, you know, that’s the root cause of ischemia, you know, I mean, at every level we want to keep things matched, right?

And a lot of problems arise [00:11:00] when that doesn’t happen. A couple of questions I had specifically. So one thing on the, sort of the goals for moderate physical activity, the 150 minutes per week target, if someone comes to you and they say, should I spread that out over the week or do it all in one day?

Assuming that I’m equally likely to do either one. Of course, the answer is always do the, do the one that you’re most likely to do, but assuming that’s true. Is there any evidence to suggest one approach is better than the other that you know of? I think in general. when you, when you look at the various ways that physical activities has been implemented in studies you know, various sort of interventional or randomized controlled studies, it seems like, um, the most important thing is total volume.

So like the total amount that you do. However, there is an additional benefit from, from frequency. And I’m kind of, I’m focusing this mainly on [00:12:00] general health benefits, but there are some studies to say, if you’re trying to gain muscle mass. It’s probably better to, to split the total amount of work that you do into two or three sessions across the week rather than doing it just once.

Although, the additional benefit is, is, is small, but there is maybe one there. But then when you look at things like the benefits of movement snacks on say blood sugar regulation there are studies where you kind of a less extreme version of the question you asked, but you say, if. You do one hour of activity a day versus splitting that up into multiple five minute sections of activity throughout the day, and you look at blood sugar regulation, which is better for, for blood sugar, that it’s the frequent, it’s the frequent movement is actually better, even though the total amount that you did in that day is the same.

So I think there is, because It’s not just that there is an active benefit of physical activity, there is a negative effect of being sedentary. It is an actively stressful [00:13:00] and pro inflammatory state. So frequency is important because then, you’re kind of spreading out the time and decreasing the time across the week where, where you’re, where you’re being actively sedentary.

So I, so I would, I would prefer, I think there is. You know, from a number of different sort of lines of evidence, I think spreading out across the week is probably going to be a bit better. Right. And that probably it’s a better reflection of kind of the ancestral archetype of how we would have moved.

And do you think is there any data specifically that you know of on an upper limit to walking in terms of steps? There’s there’s no upper limit in terms of, or there doesn’t appear to be an upper limit in terms of. Overtraining or whatever. So, yeah, overtraining. Mmhmm. Most studies suggest that once you get above…

And it depends from study to study, but somewhere between 14, 000 and 20, 000 steps a day, the benefits start to level off. Whereas it’s linear up to that [00:14:00] point, like the more steps, the better, and you’ll get the same benefit for each additional, say, thousand steps you do. But then somewhere between, yeah, 14 steps, it just, it levels off.

So it’s never actively detrimental. But the continual added benefits start to drop off. Great. Okay, excellent. Thank you for those answers. That’s super helpful. And thank you to Steve for asking the question. If you have any questions yourself about this topic or anything else in the realm of brain health and fitness, feel free to send it our way at All right, we will see you guys in the next episode. Thanks so much, Tommy. Thank you. Thanks, everybody. Bye bye.