New Book Offers Latest Science on Nature-vs.-Nurture Debate

An interview with David Epstein, author of The Sports Gene.

Thursday, August 1, 2013, 12:00 am
David Epstein, author of The Sports Gene.

Sports Illustrated senior writer David Epstein has just published his first book, The Sports Gene, which analyzes the genetic research and unique athletes reshaping the age-old nature-vs.-nurture debate. Below, Epstein discusses what genes can tell runners, from elite performances to our own training and health.

While doing the reporting for your book, what was the most surprising thing you learned about how genetics contribute to distance running success?
David Epstein:
In general, I did not expect there to be so much evidence for genetic and biological influence on the drive to be physically active. Intuitively, I knew that people have different personalities. I know some of my friends would rather plop on the couch, and some of them can't sit still and start to go a little nutty if they aren't working out. Some guys who I ran with in college [Epstein ran track at Columbia University], once their running career was done, took up cross-country skiing, or got big-time into cycling. A couple of the others were really good at competing and, as soon as that was done, never ran again.

When I started looking into the biological basis for physical activity, in the scientific literature it's clear that the dopamine system, which is the reward system in the brain, responds to physical activity. There's no question about that. But it's also pretty clear that it actually drives physical activity as well. Scientists have engineered animals that have dopamine systems that make them want to be physically active, and get depressed and anxious when they aren't. And the more activity they're bred for, the more anxious they get when they're not being active.

There's every reason to believe that in humans it functions, to some degree, the same way. We’re used to thinking that voluntary actions are completely our agency. And they still are—like, you can still get up off the couch, but you might be less likely to do so. That was a topic that I didn't expect to get into at all.


In the chapter where you discuss that science, you talk about Pam Reed, the ultrarunner, and her genetic advantages in terms of willpower. It’s almost more acceptable right now to look at somebody and note his or her clear physical advantages—but the notion that grit and determination could be innate might discourage some people. What would you say to that?
That gets to the root of some of the concerns I had when I was writing the book and that I have in the field. Scientists will find either some environmental or training input, or some genetic input, and will often act like that means the other one doesn't exist. Any explanation that it's all nature or all nurture is a straw-man argument. Unfortunately that's what we usually see in pop science writing. You just take one line and stick with it.

I think while it's quite clear that some people have a greater innate drive to be physically active, that just means for some other people, maybe they need to work a little harder on their environment. I can tell you for sure, having a running partner makes such a big difference for me. It was amazing to hear Pam Reed say that even now she literally gets anxious and jittery if she isn't moving around all the time—which is exactly what happens in the mice that are bred for physical activity.

I’m not like that, so I think for someone like me—I’m still an active runner—I just have to work a little harder to make my environment better. I don't think it should discourage people. Frankly I think that's a huge portion of what we talk about in the running community is how you can manipulate your environment to get the best out of yourself.

What would you say is the most common misunderstanding about how genetics can influence distance running success?
Among laypeople, I think the biggest misconception is that genes are destiny as opposed to predisposition. The vast majority of genes now, it looks like, just shape your biological predisposition. They aren't certain destiny. Now, that's not true in every case. The genes that give you ten fingers and all the brain chemicals you have and your organs—those are pretty deterministic. But that's the vast minority of traits. Most other traits, genes work in broad networks. They depend on one another and don't crowd out human agency or free will.

But it might mean that you need to manipulate your environment in different ways. Somebody will have, for example, a gene that predisposes them to having brain damage if they get hit in the head. You see this with NFL players. And that doesn't mean that person is going to have brain damage for sure; it means they'd have to manipulate their environment to get hit in the head less if they want to be on equal footing with everybody else. And that's for the vast majority of genes.

When the human genome was first sequenced, scientists did think they would find more single genes that would say "you're like this," or "you're like that." But what's emerging is that genes push you this way or that way, but you have to interact with your environment to have some outcome. Every week I see news wire stories about a new gene being found. It's like: "The Alcoholism Gene," or "The Lazy Gene," or "The Angry Gene." And that sort of language I think is really counterproductive because it make it seems like you can't do anything about it, and that's not the case.

You talked a little about surroundings and how different variables other than genes can impact you, and one of the big questions discussed in the book is: Why do East African runners dominate in distance events? How much of it is genetics?
One place to start with is this idea of an "East African" phenomenon. Take the Kenyans, for example. It’s really a Kalenjin running phenomenon: one tribe that is 10 to 12 percent of the population of Kenya. Millions of Kenyan kids all over the country run to school, for example. For the most part, only the Kalenjin kids emerge. Millions of kids in India run to school and they're not emerging as great runners. It’s really the Kalenjin in Kenya and the Oromo in Ethiopia, neither one of which account for most of the population. Even the winner of the London Olympic Marathon, Stephen Kiprotich, who was from Uganda, is actually a Kalenjin. Same tribe, different country.

The Kalenjin have a couple of things in common, both environmental and genetic. As far as genetic features, they have among the world's most "linear" builds: their pelvic breadth is incredibly narrow and their limbs are extremely long. Having proportionally long legs makes you lighter, so you have better running economy. They have their ancestry in a really hot and dry climate and, like all organisms—not just humans—that evolve at low latitudes in hot, dry climates, they have elongated limbs for the purpose of cooling. It’s the same reason why your radiator has coils: to increase the surface area compared to the volume. There was just a study out that shows that Kalenjin runners also have longer Achilles tendons, which is good because they store more elastic energy. And they have “distal elongation”: not only are their limbs long, but they get longer and thinner as they go outward. That's hugely important on running economy.

For example, in studies where eight pounds are put on a runner's waist, it decreases running economy because the runner is heavier, but only a little. Then if you move a four-pound weight down to each ankle, it makes a huge difference. So, look down: If you have thick ankles, you're just not going to win the New York City Marathon. I'm sorry, that's just a fact. It's like swinging a pendulum. This is why Oscar Pistorius has the same running economy as [former marathon record holder] Paul Tergat, because he has these inhumanly light lower legs.

In addition to a linear build, the Kalenjin and Oromo both have low-latitude ancestry. Which means that they're genetically adapted to sea level but yet they're all growing up at 8,000 feet. If you live at altitude prior to puberty as a kid, you end up with a larger surface area of your lungs, which is good for your aerobic power.

I think if Kenya turned into Finland tomorrow—this First World country with no poverty—I think the running phenomenon would be done. But even if you put Finland back in between World War I and World War II, when it was a poor country, and assume the socioeconomic circumstances of Kenya, I don't think it would turn into Kenya. Even the rest of Kenya isn't turning into that little sliver of Kenya. So I do think there are innate biological traits without which we wouldn't see this phenomenon.

Speaking of body types, another interesting part of the book was the discussion of the "Big Bang of Body Types," the physiological specialization that's happened over the last century from sport to sport. Long ago, it was thought that average body proportions were best for any sport. Today, however, you have, for example, tall basketball players and tiny gymnasts. You talk about the advantages of distance runners becoming smaller over the years, but then you also give the example of [women’s marathon record holder] Paula Radcliffe, who is 5'8". What makes her success unique? 
Paula is way taller than a lot of the people she runs against. She's not extraordinarily tall, but she is for a marathoner. [Physiologist] Andrew Jones has tested her since she was a teenager, and he suggested that that was actually one of her advantages. She already had a VO2 max of 72 when she was a teenager without hardly training—close to as high as women get. Over the next decade of her training, her VO2 max didn't really improve, but her running economy got better year after year after year. Part of that Jones attributed to her legs being longer while her body weight stayed basically the same.

But one thing I look at is that she's never even in contention in warm weather marathons. A physiologist I talked to for the book suggests that's because when it gets above a certain temperature she has so much more trouble cooling at the same pace compared to women she's running against. So if you look at the Olympic marathons she’s run in, the winners were 4'11" and 5'2" or 5'3", and Paula Radcliffe isn’t even in contention. During that same time period, in the prime of her career, she was absolutely unbeatable when the weather was cool.

When a human gets bigger, their volume expands in three dimensions while their surface area only expands in two. As they get bigger, they get worse at cooling because they're creating more volume and less surface area. So I think while Andrew Jones might suggest that Paula’s increased leg length improves running economy, I think her overall increase in size seems to have put her at a big disadvantage in any warm weather marathons.

Since you began working on this book, how has the perception of the prevalence of doping in elite running changed? It's kind of a weird frontier now, where it seems like the science and the law are in a perpetual footrace.  
What you call a "footrace” is interesting because when I look at the World Anti-Doping Agency data, not just for running but for all sports, even as the technology gets much, much better, the percentage of positives stays between 1 and 2 percent per year. I've talked to a lot of people about this, and they believe that basically the dopers and anti-dopers are in lockstep year after year. The technology gets a little better; dopers get a little better. But the percentage of positives doesn't change.

I think a major perception that changed with respect to distance runners within the last year and a half has been more people letting go of the idea that the Kenyans might be too quaint to dope. There has been very little testing in Kenya. Now there's some testing, there have been a couple of positives, and, frankly, having been there and seen the circumstances, you ask yourself, Why wouldn't they?

I looked at data for Major League Baseball, and if you saw the graph of the likelihood of a player from a certain country testing positive, it’s almost perfectly inversely proportional to the GDP of the country he's from. That suggests to me that either people from the poorer countries are less sophisticated dopers, or maybe, more likely, their other options are not that good. I think there was a time, like when I was running in college, that people felt that just because of their rustic circumstances, that there was no way any Kenyans were doping. I think people are letting go of that idea now.  

Do you feel that doping is a more of a problem in sprinting or distance running? Or is it nonspecific? 
I tend to think it is more of a problem in sprinting, although I should say my experience from having done this in a number of other sports has been that even the athletes in the sports themselves have no idea how prevalent doping is. The only sport where I did some reporting where I got the sense the guys knew more or less how prevalent it was was cycling.

I tend to think that it might be more prevalent in sprinting because we see more positives there. A lot of drug use came out of things like weight lifting and power lifting and guys who I think had more inroads into the world of sprinters. My perception from both the data on positives and retired athletes that I have talked to is that doping is an issue in every sport that exists, but I think it has deeper roots in sprinting, and certainly a longer tradition.

Another interesting story that you told in the book is about [former mile world record holder] Jim Ryun. Can you talk about his unique genetic advantage?
Probably the most famous exercise genetics study of all time was called the HERITAGE Family Study. It was this consortium of five universities that took DNA from about 100 two-generation families and put them on five months of identical bicycle training. They found that the participants—none of whom had prior training—had this massive range of VO2 max increase. Fifteen percent had no improvement, while 15 percent of people on the exact same training improved their VO2 max 50 percent or more. It had nothing to do with how good they were to start. Families stuck together along this improvement curve, and in 2011 these researchers found a number of genes that predict a lot of an individual's ability to improve with training.

Jim Ryun’s story is a great one to illustrate someone who is a “rapid responder” to training (such as the HERITAGE participants who greatly improved their VO2 maxes).
He was a terrible athlete in middle school. He joined the cross country team his freshman year in high school just because he wanted a varsity letter and had been counted out from other sports. He was something like the 14th guy on the “C Team” when he first started. And doing the same training as the other guys on the C Team, he starts—almost by the week—moving up the team to the point where, by the end of that season, he's the top runner and they win the state championship. Literally in just one season. He takes some time off, thinking, I don't know if I'm really committed to running. Then he comes back for track season. He goes from like a 5:40 miler at the beginning of cross country season to 4:08 during track season, even with the time off. His training response is just unbelievable.  

And you could see that throughout his career. Even when he was adult, a world-class runner, he would take time off and you could see his VO2 Max go down into the 60s. Jack Daniels tracked him. As soon as he started training it would go right back up to 80 or 81. That's exactly what the HERITAGE Family Study researchers documented in people of lesser accomplishments than Ryun. We're used to thinking that challenge is something that pre-exists any kind of training, and what genetics science is making clear is what's much more constant and probably important is actually your biological set-up to be able to benefit from a particular type of training.  

What kind of genetic testing is out there now that the person on the street who wants to find out more about his or her abilities can do?
It's a little hard for the person on the street. Some genetic testing is available; but most of the genetic testing that's marketed directly to consumers is total rubbish. They're using genes that aren't very well proven. It's not really clear how they impact things. Sometimes the effects are really small. Unfortunately most direct-to-consumer testing has marketing that's way, way beyond the actual science.  

There's one scientist in the book who will do muscle biopsies of athletes and tailor their training plans accordingly. That helped him tell the guy who went on to become the bronze medalist in the Olympic shot put that he wasn’t doing the right kind of training. He had this huge proportion of fast-twitch muscle fibers, and the scientist told him he should change his training to short periods of incredibly intense lifting. He did the same thing with a distance kayaker, who had almost completely slow-twitch muscle fibers in his shoulders. The scientist told him to switch to longer races, and the guy instantly became one of the best competitors in the world.

I don't think most of us should be doing biopsies because it's an invasive procedure and we don't have great access to it. But I do think we should pay more attention to the kind of training that we see benefits from. This made a huge difference for me. I started running track as a junior in high school. I was going to run cross country for the first time my senior year and I tried to make up for lost time by running a ton of miles. I got up to 80 miles a week, more mileage than probably 99.99 percent of high schoolers—and I ran even worse. It totally killed my speed. And I remember then getting back into speedwork, and even my distance times would get better. When I ran in college, when I focused on 200s and 400s, my mile time would improve. Even my cross country times would improve.

In the book, you tell the story of your high school teammate, Kevin Richards, who collapsed and died at the end of a race because of a heart condition, hypertrophic cardiomyopathy. That's a different case where understanding your genes and how they interact with your running can have a major impact. What can a parent of a young runner do to avoid such a tragedy?  
Right now we're actually going in the wrong direction in terms of protecting athletes because an increasing number of states are allowing practitioners like chiropractors or even herbalists to do pre-participation screening for high school sports—and they have no cardiovascular training. They are not going to know the difference between a heart murmur that's just from your heart getting stronger with training, and one that could be dangerous. We're talking about these really expensive solutions, about screenings that are never going to happen, giving every kid an EKG. Never going to happen. We're ignoring other low-cost solutions that can save some people—like having people who really have cardiovascular training do pre-participation screening.

Many distance runners, if not most, are going to have a heart murmur when they're in really good shape. Because your heart is a muscle, like any muscle, it grows when you work it out. And so as you increase the strength of your heart you could have what's called a physiologic heart murmur that will go away when you get out of shape. I would have a heart murmur when I would show up in high school or college and have my pre-participation physical. Distance runners are very likely to be told—as my friend Kevin was—"You have a heart murmur, but of course you do, because you're a distance runner and in really good shape."

I would encourage any parent of a distance runner who has a heart murmur to take them to a cardiologist, particularly one who has a specialty in hypertrophic cardiomyopathy, or at least is familiar with it, because there are differences in the dangerous kind of heart murmur and the distance runner's heart murmur. But only specialists can check that.

If someone in the family has died from cardiovascular reasons, say, before the age of 50 or even 60, and you can get DNA and find that they have one of the recognized genes for HCM, then everybody in the family should get tested. If they find out that you have this gene, maybe you can get an implanted defibrillator. That's an area where genetic testing has made some big differences for patients right now. An athlete drops dead on a field at least every other week. One in 500 Americans have the condition. This is way more common than people think.

Are there any other very common, preventable health risks that distance runners can learn about themselves through genetics?
That's the most obvious one, but there are other heart conditions, like Long Q-T Syndrome, the other sudden death condition that people should look out for. The reason we love running is it's great for us—except for the people who have some of these underlying conditions, in which case it could be deadly to them.

People can now get tested for other “predisposition to injury” genes that have to do with tendons and ligaments. Genes that code for collagens, the so-called "body's glue," that basically holds your tissues together. There’s a company that just started called Genomics. A doctor has to order the test for a patient, but that's pretty easy if a patient wants it. I think people have to be careful about how much stock they put in the information, because it just tells you a little bit of information about certain risk factors.

There are other things you can do—you can strengthen sport muscles. You can stay out of certain environments. It's the same reason people rehab after having surgery, so they prevent a certain injury that they're predisposed to having from happening again.

What do you want distance runners who read your book to take away from it?
One thing that occurred to me as I was putting this together is that some things that we think are genetics might not be, and other things that we think are completely acts of will—like the drive to train—might actually have very important genetic components. So really, even though we sort of fit stories to what we think is going on, we can't observe the genetics; we don't know what's really going on.

I would say to any distance runner: If you train with a partner and you're not getting the same results out of it as he or she is, the problem is very likely you in the deepest sense of the word. It's probably your genetics, and you should try something different. I was often afraid to try different training methods. You get into a groove, and you don't really want to change things, and distance runners are creatures of habit. But there are people in the book like Chrissie Wellington, the greatest female Ironman triathlete of all time, who because she dared to try something completely different found that she had talents she didn't know about.

I think most people feel like there's some sort of minimum mileage you have to put in to run a certain distance. But if that's not working for you, try something different. Unfortunately, right now you can't see your genes, so I really think people should go through a period of experimentation with training and not stick to something just because it works for somebody else.


Amby Burfoot's Review of The Sports Gene