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I was walking to work today, and I got run over a few times by gaggles of joggers on the streets of New York. They're here en masse because this weekend, 40,000 people will be running, jogging, walking the 26-mile New York City Marathon. And hundreds of thousands will run in marathons in other parts of the country, other parts of the world this year. What compels so many people to train for so many months, sustain so many injuries that they do just to compete in a really grueling race?

My next guest says this type of running is what humans are fine-tuned to do. It's what our bodies are made for. And not only that, it might benefit the brain as well. Dan Lieberman is a biological anthropologist at Harvard. And by the way, he is planning to run the New York City Marathon. Welcome to SCIENCE FRIDAY.

Professor DANIEL LIEBERMAN (Human Evolutionary Biology, Harvard University): Thank you.

FLATOW: Are you out there today, jogging around New York?

Prof. LIEBERMAN: Actually I'm still in Cambridge, getting ready to drive to New York.

(Soundbite of laughter)

FLATOW: Much more dangerous than jogging.

Prof. LIEBERMAN: Absolutely. It's the most dangerous part of my weekend.

(Soundbite of laughter)

FLATOW: John Ratey is an associate clinical professor of psychiatry at Harvard Medical School and the author of �Spark: The Revolutionary New Science of Exercise and the Brain.� Welcome to SCIENCE FRIDAY.

Dr. JOHN RATEY (Psychiatry, Harvard Medical School; Author, �Spark: The Revolution New Science of Exercise and the Brain.�): Well, I'm glad to be with you.

FLATOW: Thank you. Dan, how do humans stack up at running compared to other animals? We don't seem to have much of an advantage at all here.

Prof. LIEBERMAN: Well, that's the standard story.

FLATOW: Yeah.

Prof. LIEBERMAN: If you think about humans as sprinters, we're actually really pathetic. So Usain Bolt, the world's fastest sprinter, can run in -about nine and a half meters in a second, right. So he's pretty fast compared to the rest of us. But he can only do that for about 10 or 20 seconds, and then he'll run out of gas.

A lion, if it was chasing Usain - and I hope that doesn't happen - a lion will run twice as fast as Usain, 20 meters a second, and can do it for four minutes. So as sprinters, we're just pathetic. We're always going to be lunch for the carnivores. But what we're astonishing at is really long-distance, endurance running. So there's really no other creature that's as good as us at running in very long distances at pretty good clips.

FLATOW: You mean we can outrun just about every animal if we do it for a long time?

Prof. LIEBERMAN: Oh, absolutely. Every year, they have various marathons where they have humans versus horses. And people always bet on the horses and often they loss because a good human marathoner can easily beat a horse over 26 miles�

FLATOW: Wow.

Prof. LIEBERMAN: �particularly if it's a hot day. Because the big advantage that humans have is that not only can we run - so we can run at speeds that make horses and dogs and ponies and most other mammals gallop. And when mammals gallop, they can't really cool down. So what happens is that they overheat at the speeds that we run at. So on a reasonably hot day, a human being can outrun pretty much any animal over long distances.

FLATOW: Well, what characteristics of our body help us to do that?

Prof. LIEBERMAN: Oh, gosh. We've got features all the way from our heads to our toes. So we have short toes and we have very springy arches, and we have Achilles tendons and all kinds of other springs in our legs. We have narrow waists. We have a large gluteus maximus. We have all kinds of cooling features such as we're able to sweat. We don't have fur. We have - I could go on for quite a long time�

FLATOW: Yeah. I'm getting the picture.

Prof. LIEBERMAN: �we're loaded with features.

FLATOW: But - and that would mean that if - let's say, back in days of the early man who was hunting, the caveman period, a caveman could just run down an animal and kill it then, because the animal would sooner or later run out of - not be able to stop and pant anymore?

Prof. LIEBERMAN: Well, I'm not so sure of it with cavemen in Europe. But certainly in Africa, where our ancestors came from, maybe two million years ago or so, maybe two and a half million years ago, we know that humans started eating meat. But projectile weapons were - are a very recent invention. So a bow and arrow is probably less than 70,000 years old. And even putting a kind of stone point on top of a stick to make a spear, that's less than 300,000 years old. So for millions of years, the best technology our ancestors had to kill animals was basically a sharpened wooden stick or a club. So we think that what humans did was use this advantage to run at high speeds that make animals overheat, to do what's called persistence hunting. And it's - people still actually practice this occasionally.

FLATOW: John Ratey, let's talk about why exercise makes us feel good, and I know this from my own personal experience. I will say, I've got to get on that treadmill for 10 minutes because I just need to get my blood going in the morning. But as I'm on there for that 10 minutes and then another five more minutes, I start to feel really good. And it wants me - it makes me want to say even longer on that. What's going on in my brain?

Dr. RATEY: What's going on is a lot of different changes. First of all, you're getting all your brain cells to work. And with that, they dump out all these great things we learned about for the past 40 years called neurotransmitters. And then they also - running also and exercising causes a release of brain growth factors that also are important in us feeling great about ourselves and keeping our brain working and functioning at its highest level.

FLATOW: Mm-hmm.

Dr. RATEY: And then, of course, we have the endorphins that are made in the body as well as the brain, more so in the body than the brain, and we get that. That also plays a role in us feeling satiated and feeling good. And then more recently, we have a group of other hormones that's just discovered called endocannabinoids, or marijuana-like factors, that also play a role in helping us stand the pain along with the endorphins that are endogenous morphine or internal morphine, as well as in the brain; it makes us feel really OK.

FLATOW: Mm-hmm. And how much running do you have to do, or walking or jogging, to start seeing these changes?

Dr. RATEY: Oh, you can see them very quickly if you get your intensity way up. But the usual case is running for 10 minutes, as you were describing it, is to get - you think your blood going or - but you're also - at the same time, you're releasing these factors, and you're turning on the front part of your brain, which is the part of the brain that helps us think and makes decisions and all of that because that part of our brain evolved from our moving brain.

FLATOW: Mm-hmm. So you're actually priming your brain, then, to do some mental work if you're exercising?

Dr. RATEY: Oh, absolutely. It gets us ready to sort an - information, make decisions, sequence our movements, helps us remember what we did before, evaluate our consequences, all these great things that add to our physical skill, as Dan was talking about, that made us evolutionary victors.

FLATOW: Uh-huh. And some schools, I understand, are using exercise to help the kids learn better.

Dr. RATEY: Absolutely. There's a number of schools across the country that are now - have developed these programs that are really so outstanding, where all the kids are moving for 40, 45 minutes a day. It's not about who's best, but who's achieving their personal best. And this pays off in their test scores and - first it pays off when we look at it, it decreases discipline problems and improves attendance because the kids enjoy school differently.

FLATOW: 1-800-989-8255, talking with John Ratey, who's author of the book �Spark: The Revolutionary New Science of Exercise and the Brain�; also Dan Lieberman, who's a biological anthropologist at Harvard. Dan, you say we have a special muscle, the gluteus maximus, if I might say it gently - our butts. Our butts are the keys for running - explain that a bit.

Prof. LIEBERMAN: Everybody wants to know about this one.

(Soundbite of laughter)

Prof. LIEBERMAN: So we're not, of course, unique in having a gluteus maximus; lots of other animals do. But it's the largest muscle in the human body. And interestingly enough, it seems to be relatively expanded in humans. So if you look at a chimpanzee, it's got a pretty small butt, if I can say that on NPR.

But we can see that about 1.9 million years ago, the gluteus maximus got really big, and we could - because we can see its insertion on the pelvis in early Homo erectus. And what the gluteus maximus does - well, it's involved in a bunch of things. So that upper portion of gluteus maximus helps you climb, and it helps you walk uphill. But you don't really use it that much in running, and I'm not sure if our ancestors were - once we got to the genus Homo - were climbing trees all that much or just walking up hills all the time - any more than say, earlier hominids.

But what it's really important at is that it fires every time your body hits the ground. Because when you're running, you're always falling. And your body wants to fall forward over your hips. So the gluteus maximus contracts, and it actually works with some of the other spine muscles and actually stops your body from tipping forward. And so, you know, any of the listeners can do this. You can just clench your rear end and kind of run around the room a little bit, you can actually feel it clenching up every time you hit the ground.

FLATOW: But it doesn't - but you never, and I'll say this gently, you never see a marathoner with a big butt.

Mr. LIEBERMAN: Oh, well, you know, it doesn't need - just remember, we have big butts compared to other creatures.

(Soundbite of laughter)

FLATOW: I see what you mean.

Mr. LIEBERMAN: So we already have big butts, all of us. Sprinters tend to have even more enlarged gluteus maximuses and also hamstrings because they're falling even harder, right?

FLATOW: Right.

Mr. LIEBERMAN: I mean, a sprint is a constant - you're falling forward as fast as you can. So sprinters really need those even more than endurance runners.

FLATOW: 1-800-989-8255. Let's go to the phones, to John(ph) in Jackson, Wyoming. Hi, John.

JOHN (Caller): Hey, how are you?

FLATOW: Hey.

JOHN: I just finished a book called �Born to Run.� It has a lot of stuff going on, but talks a lot about how modern running shoes have been a bad idea and have hurt a lot of people. Any comments there?

FLATOW: Dan? What, do we run better without shoes? You see all these, you know, marathon runners, they don't have shoes on. The winning ones from Africa, they're not wearing shoes.

Mr. LIEBERMAN: No, the winning runners are - actually are all wearing shoes. But you can run barefoot without shoes. Abebe Bikila broke the world record and won the Olympics in 1960 running barefoot. I don't think you need to have shoes to run. Shoes can be pleasant and comfortable. I think the big debate really is not whether shoes are good or bad for you, but whether the very recent models that many people are wearing, with high heels and lots of cushioning, are good for you. And to be honest, at the moment, most of the evidence that people are using to discuss this is very anecdotal. I myself love to run barefoot, and I'm pretty sure that barefoot running can be very good for you. It strengthens your foot. It forces you to run in a way that's very healthy. But I don't - I think the most important thing is for people to run and enjoy it, and to do so in a way that doesn't make them injured.

FLATOW: But we evolved without wearing shoes.

Mr. LIEBERMAN: Absolutely. And again, people can run barefoot. I mean, I have to say, I really love running barefoot. It's quite fun. And I think that the way in which people run when they're barefoot is actually very healthy. And so the idea that you need shoes in order to run, or need shoes in order to run well, is obviously false.

FLATOW: Uh-huh. 1-800-989-8255.

John Ratey, you know, we talked about this boost you get from running. Can it really cause you to push yourself too hard?

Dr. RATEY: Oh, sure. That's what happens. You - people that are running all the time. Then people who get into marathons and ultra marathons, the biggest problem they have, usually, is when they do it too much and too hard and too long, and they end up injuring their joints.

And that's how I got very much interested in exercise as a mental health issue because I saw - I grew up in Boston during the Boston Marathon craze when it was beginning. And as a psychiatrist, I began to see people who had injured themselves because of overdoing it. And the first thing would happen is they'd get depressed because they couldn't run anymore and that they're - they weren't giving themselves the necessary jolt of the neurotransmitters that we talk about so much in depression and anxiety control. And then after that, a lot of them showed up with having attention problems, problems focusing, problems staying with their projects or get - staying motivated. And this led to a whole interest in attention deficit disorder, which a lot of people treat with constant activity.

FLATOW: 1-800-989-8255, talking about runners and the marathon this hour on SCIENCE FRIDAY from NPR News.

Let's see if we can get a phone call or two in there. Let's go to Jim(ph) in Little Rock. Hi, Jim.

JIM (Caller): Hi, how are you?

FLATOW: Hey there.

JIM: My question is, I was wondering if all people have the capacity to perceive the positive effects of neurotransmitters and endorphins when they exercise. Because personally, I exercise on a regular basis; I run to try to stay in shape, but I have never felt particularly good while, or following, an exercise compared to many people that I know.

FLATOW: Good question.

Dr. RATEY: It actually is about anywhere from 5 to 8 percent of the people who do exercise do not feel that positive jolt. You know, there's a big difference between the - as you describe - doing your 10 minutes in the morning and feeling ready to go and feeling the endorphin rush that got so popularized in the '70s, when we first discovered endorphins and found out the endorphins were raised in people who went fairly long distances. But not everybody gets that. Not everybody gets that jolt and that rush.

But most of us feels satiated, feel content. A lot of people are just glad that they're done with their daily exercise. But marathoners, you know, tend to really feel they need it, and they can't stop themselves.

FLATOW: Jim, you don't sound like you need to have it. You just like to enjoy run - running.

JIM: Well, I mean, I exercise. I'm one of those that tends to battle my weight, and I exercise when I have to.

FLATOW: Yeah.

JIM: But there's nothing that draws me to it and makes me want to go out there and do it. And it makes me also wonder: Could there be any sort of genetic predisposition toward people who enjoy running because they happen to have the perception of the highs after they do that versus people who might not have that, and they have more tendencies to be obese because they just don't gravitate toward exercise?

FLATOW: Yeah. Good questions.

Dr. RATEY: I think that's true. There is - there are all these differences. There's the whole spectrum. It's not an either/or most of the time. But there are some people who don't get that feeling of satiation or feeling of - that they're more complete, and that they feel better and they feel ready for the day. They've - some people don't get that. But most of us do feel that.

FLATOW: Dan, any comment on that?

Prof. LIEBERMAN: Well, it's an interesting point. I think one of the things to realize is that we live in a very weird world now, where most of us don't ever have to do any exercise at all if we don't want to. We do it on a voluntary basis. But before the origins of industrialization and before the agricultural revolution, pretty much every day, everybody every day had to do a lot of work, and often that involved running. So your average hunter-gatherer has to walk 10 to 15 kilometers a day and very often, they do a lot of running and they climb and they dig, and they do all kinds of things. And so we didn't really have any choice for most of human evolutionary history. And I suspect that there probably were - less selection for the kind of enjoyment the - you know, endocannabinoids, etc., that really do make running a lot of fun. But you know, natural selection didn't really have to work on the sedentary humans among us because until recently, there weren't such a thing as sedentary humans.

FLATOW: And can you get that - the high just from walking, also, if you're not doing the big jog, John?

Dr. RATEY: Yes. It's harder to do. One has to really walk longer distances. But certainly, walking is great - and it's better than sitting. As Dan was just saying, I mean, the hunter-gatherers did -where we came from, we really were moving quite a lot during - each and every day. And so - and walking and foraging was a big part of what we did.

FLATOW: I'm going to have to stop it at there because we've run out of time. I want to thank you both for taking time to be with us today.

Prof. LIEBERMAN: My pleasure.

FLATOW: You're welcome. Dan Lieberman is a�

Dr. RATEY: Thanks for having me on.

FLATOW: You're welcome - biological anthropologist at Harvard. John Ratey, associate clinical professor of psychiatry at Harvard Med School and author of "Spark: The Revolutionary New Science of Exercise and the Brain."

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