Running: Will It Wreck Your Body?

Hi, I'm Aketty Foster Keys, filling in for Wendy, and you're listening to Science Versus. The show that pits facts against 5Ks. Today on the show, running. More than 28 million people go running every week in the US, according to one survey. And the reason why we do this is presumably because it's good for us, right? And not only that, but We Hear Running can give you this sort of amazing feeling. It's time to get hot. Runners high that is.

I had ran two miles straight and I experienced a runner's high for the very first time. It was so freaking cool. It was like full adrenaline. So a lot of us are excited about the benefits of running. But then we also might have this nagging voice in our ear that's kind of just like, you're gonna get hurt. Everyone I know that starts to get into running, their body slowly starts to fall apart. Don't run, period. I'm so tired of saying it. Your knees go, your ankles go, your hip goes.

Running is terrible for you and anybody who runs a marathon I think needs mental health help. And so today we're running down the science year. We're gonna figure out what actually happens to our bodies when we run, what's going on with our muscles and our And then we're also going to look into runner's high and figure out like what's happening in our brains when this happens. Because when it comes to running, there's a lot of Their body slowly starts to fall apart. And then their science.

That's coming up after the break.

Welcome back. I'm Aketty Foster Keys, and today we're looking at running and what it's doing to our bodies. With me today is senior producer Meryl Horn. Hey Meryl. So are you a runner? I am a runner. Like I don't run as much as I used to, but I love running. It's like my little escape, you know. I love it when I'm listening to the music and getting into the rhythm. I actually publicly hate running, but secretly kind of love it. Uh I don't do it as much though because I got hurt.

Yeah. I mean, I'm also scared right now to really get back into it since my husband got super injured from running. Like he he wasn't doing anything that crazy, but he ended up getting a stress fracture and literally like just couldn't walk one day because of it and ended up being on crutches for Like two months? Oh my god. Which I just didn't even realize could happen. So that that really freaked me out. Please.

So that's actually where I wanted to start with injuries. Like, how likely are you to get hurt as a runner? And I wanted to compare running with stuff that's also pretty accessible. So I looked at cycling and swimming. And there are lots of studies. They'll survey people about what they do and if they got hurt.

So like one review will look at runners over a period of time to see like, okay, how much did you run? What kind of injuries did you get? Another review will look at cyclists and then swimmers. Okay. And when you look at these reviews side by side, what you find is that runners do get hurt more often. They do. They so it's not just in our heads. Runners actually are more likely to get injured. Yep. Okay. That's sort of satisfying actually.

Right? The actual numbers, they kind of differ across studies. So one big review that I found said that typically half of runners get hurt every year with an injury that keeps them from running. For a little bit. So about half of runners get injured every year. Yeah. Wow. Oh okay. That sounds pretty bad. Um and so what types of injuries were they getting? Yeah, so it's basically the stuff that you'd expect, right? From the knee down.

OK Uh the best review that I could find on this looked at 42 studies and found that generally the most common type of injury was in the knees. Okay. I was about 30%. Next up, about 20% of injuries were in the lower leg. So that's between your knee and your ankle, like your shin area. And then about 13% were ankle injuries.

Okay, but so generally knees on down, bad news for that part of your body if you're a runner. Yeah. Do we know why this is happening? Like is it just that like impact of the grounds, like your body pounding on the pavement? Yeah, so that's one thing that we thought for like ages, right? That it's wearing tear. After all, running can be super hard on your body. Every time your foot hits the ground, your knees absorb more than four times your body weight. Woof. Okay. Yeah.

That's a lot. Doesn't seem like that would be good for the joints. Right, it doesn't. But then for some people, they run and they're just fine. So I wanted to know what puts us at risk of getting hurt while we're running? And is there anything that we can do about it? So I called up a researcher who did a big study on this. His name is Dr. Rasmus Ostergaard Nielsen. He's an associate professor in the public health department at Aarhus University in Denmark. And he's also a runner himself.

But he wasn't always as keen on it as he is right now. So I heard that you got into running because you came in dead last in a local race in your hometown. Yeah, that was absolutely correct. I signed up for uh road race with a a friend and I really, really had to uh fight my way through and uh I came in second last in the race. Um and that really was the start of my running career.

So since that humbling defeat in the road race, Rasmus has pretty much made running into his science career. And last year, he published this paper that looked at why so many runners are getting knocked off their feet by this sport. Many runners say oh I had this single run where I just ran too far and then my need starts to hurt. And I thought okay, this actually challenges me.

The assumption that we have from clinical textbooks, which would describe that uh overuse injuries amongst runners develop gradually over time. Um, over weeks. So Rasmus put together a study to look for patterns of when people got hurt. He and his team followed over 5,000 runners for about a year and a half and looked at how much they ran on average and then took a look at the times where they ran more than their average distance.

And also took a look at how often they got injured after those runs. And what Raspis found was pretty wild. If you run just a little bit farther, You increase your risk to up to sixty percent larger. Oh, that's a lot. Yeah that's it's quite a lot. Hmm. Yeah, so for that big increase in risk, Rasmus saw it when people upped their distance just ten to thirty percent over their longest run the week before.

Just making that small change, that's when people had a sixty percent higher chance of injury. Oh, so you gotta be really careful, like you're not messing around when you even just go that little bit more. Yeah. So Rasmus says that you can bump up your distance safely, but in order to do that, you shouldn't run more than 5% farther than what you use. usually do. Got it. Five percent more. Okay. So like don't don't get too excited. Like just take it's really slow.

Yeah, I mean kinda like don't get it excited at all of It's like... It's really not that much more. I asked him about it. So I'm like, if I run 5K most of the time in my next training session I wanna run farther. Um, that means I can't even go six K. No you can't. Six K would would would then be a twenty percent increase. I think that most runners would be really upset to hear this.

Yeah, but but still uh numbers doesn't lie and if you want to be in the safe zone then then you need to to reduce the length of of your running session. This is actually very satisfying'cause I thought my husband was ramping up slowly, but he was not going that slow. So now I feel like we have an explanation for basically why he got so injured,'cause he was going up Yeah, at least a mile every week. And apparently that's crazy to do that much. So okay.

And obviously there's individual differences here, you know, like your friend might be able to do a little bit more running than you without getting hurt, but five percent is the general rule that Rasmus is suggesting. Okay. And even Rasmus, who's an expert in this field, has a hard time with keeping himself from running more than he should, right? If a friend come and say, Okay, Asmus, uh should we go out on a uh long run and and we should do that very fast and I get excited.

I lose my mind and even though I know when I go out for this running session this is totally stupid. I really shouldn't do this and then I sustain an injury. Yeah, and actually one of the reasons why we might have this impulse is that our body can kind of give us mixed signals here. Because there's this kind of cool thing that's going on when we run. So as you're putting pressure on your body.

You get micro injuries, micro cracks in your bones, changes in the collagen of your tendons, and when those heal. You actually get stronger. So over time, running can be really good for your body. Like runners tend to have less arthritis in their knees. Okay, wait, so in general you're you're running along, you're getting these little micro cracks, but that's actually a good thing because then when your body heals it like builds back stronger.

Yeah, but that process can take a while, you know, like it can take bones months to heal and get stronger. And for tendons, it can be pretty similar, but it ranges. But there's this other part of our body that tends to adapt a lot faster. Our cardiovascular system. So you might find that you start out like huffing and puffing, but then pretty quickly, maybe even within a matter of weeks.

you might start to notice that you're breathing easier and your heart might not feel like it's beating out of its chest so much. So then you might get a little carried away because you're like, I can do this. I feel so much better. But you don't know about those microcracks in your bones. Or do you'cause your shin is acting up and you're just deciding, well, I wanna keep running anyway. Right, right.

So the slow ramp up is important. Okay. And a lot of people talk about your form here, you know, your stride. There is some evidence that switching from running on your heels to running on the balls of your feet can reduce the load on your knees. But at the same time, doing that could also shift more of that force onto your ankles and your feet. All right, so there's no secret stride that science is saying this will save you from getting injured.

Right. Like overall it's just not super clear that making these changes reduces your risk of getting injured. Rasmus told me that the slow ramp up probably makes more of a difference here. Okay. Good to know. And there's another big thing that you can do here to prevent yourself from becoming, you know, just another running statistic. Like what? Meryl, it might be time to start getting ass to grass and building up that booty. So the butt can save us if we have a really strong butt.

Yeah, so there is this one study that looked at runners who were training for the New York City marathon and they got them to do these exercises to see how strong they were. It was stuff like planks, single leg glute bridges, push-ups. So they would like see how long they could like hold One of these poses. Yeah. See how long they could hold a post, see how many push-ups they could do, stuff like that. Um and then they looked at who got hurt and who didn't while they were training. Uh-huh.

to see if any of their strength made a difference. And what they found was that the only exercise that made a difference was the single leg glute bridge. It was the only one that cut down their injury risk. Wait, what's a single leg glute bridge? Okay, so in a regular glute bridge, you lie on your back with your knees bent and your feet flat on the ground, and then you push through your heels to like lift your butt off the ground. Okay, like a bridge pose in yoga.

Yes. But with the single leg glute bridge you're just doing it with like one leg instead of both on the ground. Okay. I can picture that. And people who could hold this for at least 20 seconds, specifically on their weaker leg, had a 64% lower risk of getting hurt while they were training. Why is the butt so important? So one explanation I've seen is that muscles in your butt help to keep your hip joints stable and also help to keep your hips and knees in proper alignment.

Huh. Yeah. So when your butt muscles are weak, the body adjusts by moving in these like new ways that can put more force and like weight on your joints. Oh interesting. Like your knees might rotate inward more or one hip might be higher than the other. get a little wonky if the butt isn't like holding everything in place. Yeah, exactly. So if you're moving differently, then like basically the Jenga stack of your body is kind of off balance.

Right. Cause it's like that's a critical piece in the Jenga Tower of the butt. It's right there in the middle. Yeah. Yeah. Yeah. So important. Wow. Newfound appreciation of the butt. Okay. And just generally, muscles are great shock absorbers. So strengthening all these muscles, you know, around your butt, your hips, and your joints. They really help to stabilize everything and prevent injury. Okay, so do the booty exercises. Do the voodoo exercises. Yes. Yeah.

So, Meryl, that's kind of all we have to say about injuries. What did you learn? I feel like I learned a lot. You know, I know to do the booty exercises and that it's also way more likely that we'll get injured if we ramp up too quickly. You're a good student, Meryl. Yay! But okay, well so I guess overall my question is still like then should I run? Like do the pros outweigh the cons? That's coming up after the break.

Welcome back. I'm Aketty Foster Keys here with Merrill Horn. Hi. And so far we've talked about injuries. You know, all the reasons why you might not want to run. But now let's talk about the benefits. Yes, finally. All right. What are the good things? So for this, I talked to Professor Duxhou Lee. He studies physical activity at the University of Pittsburgh. People call me D C as in Washington D C

So DC did this huge study a while ago that was focused specifically on running and longevity. It looked at over fifty-five thousand adults over fifteen years. And what he found was basically that runners live longer. Okay. Running was associated with significantly lower risk of death compared to not running. And here they specifically looked at cardiovascular disease and something that's called all-cause mortality. Okay. Oh and both of those things were lower in the in the runners.

Yeah, yeah. Both of those things were lower. Nice. And DC told me that the reason why running increases longevity is because it does things like lower your blood pressure, improve your cholesterol, and improve your glucose levels. So, all this stuff is super important for your heart. Okay. It also can reduce chronic inflammation, which is linked to a whole bunch of diseases. I mean it is nice to hear. It's not surprising.

Yeah. Now it's possible that people who are already healthy and therefore likely to live longer anyway, that they're also more likely to be runners. Oh right. But the study did try to take that into account. Okay. Well that's really I mean I feel like that's so different from all the scary TikTok doctors that I've seen. Like if it's overall gonna make us live longer, it can't be that bad for us to run. TikTok doctors are leading you astray, Meryl.

Yeah. And it brought up another question for me, which is like, how much do I actually have to run if I want to live longer? People may think, no pain, no gain, you know, well the more the better regarding exercise and health, right? But what DC found kind of turned that idea on its head. Hmm. His study found that people who ran less than one hour per week basically got the same benefit as people who ran more than three hours per week when it came to longevity. Whoa. Yeah, here's DC.

I was surprised that uh doing war was not you know, was not providing more benefits. You know, when I published that original paper. Lots of serious runners were unhappy. Because you know again the benefits from pushing further was more. So it really doesn't matter. Like you don't need to worry about running extra hard if what you're going for is like a boost in your longevity. Yeah, exactly. And you can even break that one hour of running down into just five to ten minutes per day. Whoa.

Five to ten minutes a day. That's it. That's all you need to do. Okay. Yeah. Nice. Uh so for DC, this is the bottom line. Moving from sitting all day, like a completely sedentary. uh to uh adding even very small, very small amount of any type of physical activity will provide health benefits. That's for sure. And we should say that even though D C study looked at runners, this goes beyond just running. You can get these benefits from other kinds of cardio exercise too. Okay, sure, right.

And by the way, all of this was especially interesting because there's this idea that our listeners brought up that running is bad for the heart. Mm. But that's not true. Yeah, that doesn't seem like it dives with what you've been saying. Right. Right. It seems like this does come from a little bit of evidence. You know, like some studies suggest that men who run a lot have a higher risk of some heart issues.

Oh. But that's men who run a ton, like 10 times more than the weekly recommended amount. Whoa, okay. Yeah, it works out to something like three hours per day. Whoa. So for that very specific group of men you said? Then they might have an increased risk for some heart issues. But for all the rest of us, we're okay. It's actually good for the heart. Yeah, so running, good for the heart, overall good for not dying. It's looking pretty good. Exactly. Okay. So it's good physically for our bodies.

Are there any like mental health benefits to running? Because it does feel amazing. Like that's why I run. We know that exercise generally is good for our mental health. Like there have been a few clinical trials that show that exercise can help treat depression. There's also some evidence that it can help with anxiety and ruminating thoughts. And on top of that, We do hear that there is something special that running can do for us. It's time to get high. Runners high that is.

So Meryl, have you experienced Renner's High before? Yeah, for sure. I mean sometimes it's It's like does kind of feel like a high. Like I get this light lightness and I'm just kind of like bounding along. I'm picturing myself like running next to the water near my house and it's just so beautiful and the music is in my earbuds and I'm just like Ha! Like it feels great. It's almost giving me life.

Yeah. And by the way, you can get this feeling from other types of endurance exercise, like biking, for example. But we hear people talk about it most specifically with running. Okay. And one study I found said that around seventy percent of endurance runners have reported having this runner's high at least once. So I wanted to know what's going on in our brain when we get runners high? Yeah, how does it happen? So for a long time, scientists had one key suspect, endorphins.

These are the natural opiates that our bodies make. Mm-hmm. They found the endorphins and they were responsible, you know, for all the feelings like eating chocolate. That's Dr. Michael Sievers. He's a scientist at the Institute of Forensic Psychiatry and Sex Research at the University of Duisburg-Essen in Germany.

And he told me that scientists found endorphins around the same time as the runner's boom, which started in the 70s. And since they were associated with all the things that could make you feel good, you know, food, sex, laughter. They were an obvious choice to explain runner's high. But then this other suspect entered the ring. Here's Michael. So in the nineties they discovered a new system, the endocannabinoid system, which is everywhere in the body.

And well, in the end there was the question, okay, is it the endocannabinoids or the endorphins which are producing the runners high? So endocannabinoids can also make us feel good. It might not surprise you, Merrill, to learn that they also work with the same receptors that contribute to other kinds of highs. Yes, the weed one specifically. And so how did Michael figure it out which one it was?

So he did a study where they basically block the receptors in our brains that get activated by endorphins. Huh. These are the same receptors that get activated if you take an opioid drug. And to block them, they actually use a medication that's given to people with substance abuse issues. Okay. If you take it and then you try to get high, you won't actually feel the high.

Yeah. And so if runners take this pill and they don't get runners high, then we know that the runner's high is the endorphins because the drug has blocked the endorphins, which means that it would block the runner's high. Okay. So what Michael Steam does is they have runners come into the lab, take either a placebo pill or the blocker, and then get on the treadmill for fifty minutes. Okay. And then before and after each session, they test for their mood and their anxiety.

The blockage of the opioid systems did more or less not hinder a runner's high. So we could demonstrate that a runner's high does not depict On End of Does not depend on endorphins. It's not the endorphins. It's something else. Like the endocannabinoids, I guess? Yeah, Michael thinks it's the endocannabinoids. Okay, so but why does he think it's endocannabinoids specifically and not just some other thing in the brain?

Yeah, so Michael and his colleagues did look at endocannabinoids in the study, and they saw that they went up during the run. Okay. And then we also have mouse studies on this. There's this one study that looked at mice running on a wheel. And this time some of the mice had their cannabinoid receptors either blocked or missing. Ha! They compared them to other mice that didn't.

And they found that the mice with the blocked or missing cannabinoid receptors ran less than the other mice by like 30 to 40 percent. Because they were l not feeling the runners high, I guess. Like they were they were kinda bummed out. So they're like, why am I even running on this wheel? What's the purpose of life? I'm gonna stop. Bottom line, it seems like the endocannabinoids are the big deal here. Okay.

But Michael doesn't think that endorphins are doing nothing while we run. There is some evidence that endorphins can do other stuff. Like we think that they can make your muscles hurt less while you're exercising or after. Okay, that makes sense. And then there's other stuff going on in our body. And one scientist told me that when you exercise, it's kind of like there's a chemical cocktail party going on up in your body. Mm-hmm.

There's also dopamine, serotonin, adrenaline, and some other stuff like all dancing around in there. Great. Okay, so the last thing I wanna talk about is if you haven't had runner's high and you want to, what should you do? Oh yeah. Yeah, can you like make it more likely that you'll feel a runner's high? Well, we don't have a ton of studies on how to get it specifically, but Michael did have some tips based on other studies about exercise and endocannabinoid.

Okay. So first he said that you should aim for a heart rate that's between 70 to 80% of something called your age adjusted max heart rate. But how generally like how hard is that? It's pretty high intensity, like pretty vigorous, but not your max. You don't want to be going like your hardest. That's helpful. And that's zone three running for people who are familiar with zones. Yeah. The other thing is that it probably won't happen if you're doing that bare minimum 10 minutes. Oh.

Oh, you have to be running for a while, which makes sense to me. I feel like I don't really hit it until it's been like a good 20 minutes at least. Yeah, that's basically what Michael said actually. He said you should be running at least Like twenty minutes. At thirty-five minutes more or less, you're having the best mood results in the studies. And well then it depends.

Which is the best setting for you? For example, if you like to run in nature, then it should be like in nature. If you like your favorite music, you should listen to your favorite music. If you like to run in groups or alone. So That's where we're landing, Meryl. How do you feel about running now? I'm excited to get back out there. Like it's it is such a good feeling and I'm excited that as long as you don't ramp up too quickly, you'll be healthier overall if you run. Oh great!

Are you gonna run more? Are you running right now? Yeah, I think this made me feel like all right, like I do want to get back into doing it more regularly. And I think that like the idea that okay, I can just start with 10 minutes a day. Okay. It might not feel good to like my athletes ego. Bye. It's what will keep me safe and consistent. Oh, and and and now I can get a fat ass too. That's what we really learned. Fat asses equal healthy running.

Like more so like a muscular ass, I guess. But you I'm definitely gonna get back into it. All right, nice. Thanks much. Thanks, Akatty. That's signs versus. There are 76 citations in this week's episode. If you want to check them out, you can go to the link in our show notes. This episode was produced by Aketty Foster Keys with help from Blythe Terrell, Michelle Dang, Rose Rimmler, Meryl Horn, and Wendy Zuckerman. Were edited by Blythe Terrell.

Wendy Zuckerman is our executive producer. Fact-checking by Taylor White. Mix and Sound Design by Bobby Lord. Music written by Boomi Hidaka, Peter Leonard, Emma Munger, and Bobby Lorde. Thanks to all the researchers we got in touch with for this episode, including Dr. Anita Iberl, Dr. Johannes Fuss, Professor Robert Otto, Dr. Hirofumi Tanaka, Dr. Peter Kokinos,

Dr. Marilyn Moffat, and Director Brian Farr. A big thanks to Joseph Lavelle-Wilson and the Zuckerman family. Science Versus is a Spotify Studios original. Listen for free on Spotify or wherever you get your podcast. Follow us and tap the bell for episode notifications. We'll fact you next week.