These Shoes Are Killing Me!

Stephen J. DUBNER: What are you wearing right now, shoe-wise?

Elizabeth SEMMELHACK: I’m wearing a pair of Vivier flats.

DUBNER: How many N.B.A. players regularly get pedicures?

Howard OSTERMAN: Ninety percent of them.

DUBNER: What kind of animals have you put in shoes?

Daniel LIEBERMAN: We put sheep in shoes, actually.

DUBNER: Have you ever had people come to you who want their foot surgically altered so that they will fit the fashionable shoes they want to wear better?

OSTERMAN: Once a week.

There’s a theory I’ve been kicking around. Not really a theory — more like an idea. Eh — barely even an idea. Let’s call it an observation. The observation is this: Very often, when we see something that needs improvement, that needs correction, we respond with an overcorrection. You see this all the time with nutritional trends. You see it in politics and government; in a lot of the rules and regulations we draw up. You see it in human behaviors large and small. Our sages have warned us against this; as one old saying goes: “Do not use a cannon to kill a mosquito.” And yet many of us are guilty of this all the time. So rather than simply correct, in measured increments, we overcorrect. That’s my observation, at least. You don’t have to agree. But I’m telling you this because I believe one overcorrection we’ve made has become so normalized that we’ve lost sight of just how extreme it is.

LIEBERMAN: We have that attitude because it’s natural to think the world around us is normal. Right? We think it’s normal to sit in chairs. We think it’s normal to eat breakfast cereal that comes out of a box. We think it’s normal to drive around in these metal contraptions, take elevators and get on the Internet. All of these things we think are completely, absolutely normal. From an evolutionary perspective, they’re not. One of those categories is shoes.

That’s right, shoes! Today on Freakonomics Radio: the social and economic history of footwear; the history of walking and running; and what our modern shoe fetish may be costing us:

SEMMELHACK: If you just added a few foot exercises to your daily routine, you might be playing cards before you know it.

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Not long ago, I was buying a case for my new smartphone. It was a rubbery protective case that also extends the phone’s battery life. And I thought, What does it say about my smartphone that, right out of the box, it needs this fairly substantial piece of add-on gear? And then, for some reason, walking out of the store, I had the same thought about shoes and feet. Do shoes represent some kind of evolutionary failure? Why does nature’s most advanced biped need to supplement its own feet with such substantial add-on gear?

LIEBERMAN: People have been wearing shoes probably for thousands and thousands of years. But the kind of fancy, modern shoes that we wear today are really quite unusual and haven’t been around for very long.

That’s Dan Liebermam.

LIEBERMAN: I’m a professor of human evolutionary biology at Harvard. It’s my job to look around the world, think about it and how we use our bodies, think about what’s normal and what’s abnormal. That’s not to say that everything that’s abnormal from an evolutionary perspective is bad. A lot of abnormal things that we do are terrific, like antibiotics, refrigerators and sterile surgery.

So where do shoes fit in? It probably helps to start at the beginning — or at least a really long time ago.

LIEBERMAN: When you walk around and see people, most of the day, you see people just walking. Right?

Right. Human ancestors are thought to have begun walking upright, at least some of the time, about six million years ago.

LIEBERMAN: But it turns out that running played a really important role in our evolutionary history.

Running was important because why?

LIEBERMAN: Because you can’t really be a hunter without being a runner.

This was long before any sophisticated weapons.

LIEBERMAN: For millions of years, the most lethal technology available to our ancestors was a sharpened wooden stick or a club.

So how did this hunting happen?

LIEBERMAN: We have abundant evidence that what people did was run animals in the heat to a state of hypothermia.

At which point the animal would lie down and could be clubbed to death.

LIEBERMAN: It’s called persistence hunting. The hypothesis really is that all these features — which range from having a spring in our feet, short toes, to having a big butt, Achilles tendon, for example — all these are novel features that humans have that that enabled our ancestors to become long-distance runners who could then chase animals down into a state of heatstroke.

And all that running was not done in Nikes or Onitsuka Tigers.

Irene DAVIS: Remember that this new technology and footwear has only been around for about five or six decades, and yet we’ve been running for two million years in either bare feet or shoes that are extremely minimal.

That’s Irene Davis.

DAVIS: I am a professor in physical medicine and rehabilitation at Harvard Medical School. I’m also the director of the Spaulding National Running Center.

Her view of feet and modern footwear?

DAVIS: We have lulled ourselves into thinking that our feet need cushioning and support to survive and to withstand the loads of walking and running. It’s very hard for people to make this paradigm shift back to really the way that we were running for the majority of our evolutionary history.

Anthropologists estimate that humans began to wear rudimentary shoes somewhere between 26,000 and 40,000 years ago. So let’s ask two questions — one small, one large. Why did we first embrace shoes? And what have they come to represent?

SEMMELHACK: See, you’re getting ahead of yourself. You’re rushing to [define],or maybe you haven’t yet defined, “shoe.”

That’s Elizabeth Semmelhack.

SEMMELHACK: I’m the senior curator at the Bata Shoe Museum.

Which is in Toronto. All right then, how do we define shoe?

SEMMELHACK: “Shoe” is a term that we bandy about to mean all kinds of things. But more technically it is something that has a sole and then it has an upper or parts that cover the entire foot. And so a boot would be a shoe then that had a shaft. The uppers continued, you know, up to the knee perhaps. A sandal might just have an upper and a thong to secure it to the foot.

DUBNER: What about the barefoot running shoes that are a rubber-ish sock for the shoe with toes?

SEMMELHACK: Yeah. What about them?

DUBNER: You do not sound very excited by them. Are they a shoe? Do you have some of them at Bata Museum?

SEMMELHACK: We actually don’t have a pair and we should have a pair. They are an interesting invention. I still find them very disconcerting when I see them out on the street.

DUBNER: Really?

SEMMELHACK: I do.

DUBNER: Because why?

SEMMELHACK: With the exception of maybe summer sandals, the foot is usually encased. Right? We don’t really see it that often. To see each toe enveloped in its own little toe casing … I don’t know.

DUBNER: It’s not your thing.

SEMMELHACK: Not yet, no.

DUBNER: It offends your sensibilities somehow.

SEMMELHACK: It doesn’t offend them. I just am still struck by it every time.

DUBNER: I see. That’s interesting. I’ll be honest with you. I’m challenging, in my mind at least, the central premise of the shoe and that encasing. I’m not a total idiot. I understand that when it’s cold or wet, or the ground is rough or sharp or whatever, that obviously you want to protect the bottom of your feet. But I also wonder at what cost we’ve encased our feet for lo these many millennia. We’ve now created many, many, many, many different forms that have all different political, economic, social signals and that’s fascinating. But I am curious if you ever step back and wonder about the necessity of this encasing strategy.

SEMMELHACK: I do, actually. When I think about Chinese foot binding — which resulted in women’s feet being around three inches in size — it seems like such a profound body modification. But the fact of the matter is that all of us who have grown up wearing footwear have bound our feet to some extent. If we were able to meet our non-shod selves in a different dimension and look at what our feet would be like naturally, they would be much larger, much more splayed, rougher. In some ways the foot would become the shoe needed to make it through daily life, because the body has the ability to build up calluses at the bottom of the foot.

That said, Elizabeth Semmelhack appreciates what the shoe has helped us accomplish.

SEMMELHACK: Shoes have been central to things like being an astronaut, living in the Arctic and venturing across hot desert. There are many places where the human spirit for adventure was probably helped by a pair of boots. It’s probably hard to summit Mount Everest not wearing footwear. Its protective quality has helped humans expand their territory. But it has been central to [human’s] expansion of class division. The true function of footwear is more about establishing who you are, what your gender is, what your status is. It functions as a communicative social tool, while at the same time, some shoes make it comfortable to walk around in. But not all.

DUBNER: When and why did women start wearing shoes that, to me at least, look to be painfully small and constraining?

SEMMELHACK: If you look at paintings from the early 17th century, like a painting of a bunch of Dutch people drinking, it’ll be women and men and their feet are all very clearly visible and there’s really no size difference between men’s and women’s shoes. But if you fast-forward through that century, all of a sudden the women’s feet are tiny in representation and men’s are much, much larger. Some of it has to do with shifts in ideas about gender. Enlightenment thinking was attempting to establish that men and women were different. Some of that finds expression in fashion. By the end of the 17th century there’s this much larger thing happening within culture that’s suggesting that men are rational and that their clothing should sort of not betray any excess interest in the fancy things in life. Women are seen as naturally irrational and frivolous. The high heel fits into that perfectly.

The shoe — like just about everything we humans wear and use and do — is a hybrid of function and form. It’s plainly useful … but part of its use lies in its ability to signal something about the person wearing it. Consider the humble sneaker — or, I should say, the sneaker that I had presumed was humble.

SEMMELHACK: A lot of people think of sneakers as being really casual. Some of them, the majority of them, being inexpensive.

In 2013, Semmelhack put together a museum exhibit on sneakers.

SEMMELHACK: But what my research showed was that sneakers actually started out as objects of luxury. The early sneakers, tennis shoes, were expensive. They reflected privilege, because in the middle of the 19th century, before the 40-hour work week, only the wealthy had the time to play. Only the wealthy could afford multiple pairs of shoes to have specific shoes to play in. Then, rubber itself was expensive, and the cost of sneakers was quite high.

So how did the sneaker cross over into an everyday thing?

SEMMELHACK: In the 1930s, one of the things that becomes a pan-cultural obsession is the physical fitness of each country’s citizenry. World War I had proven to the world that there were not enough fit men to fight a war. So as World War II was brewing — eugenics and ideas about racial superiority obviously led to fascist concepts — and countries around the world began to insist that their citizens exercise to prove physical superiority or ethnic, racial superiority. But also to get ready for the next war. In many ways, it was this moment of fascism that democratized the sneaker.

Speaking with a shoe historian like Elizabeth Semmelhack, you get the sense that every kind of shoe imaginable has a similarly winding history, like the sneaker’s; a similar blend of form and function, and — this is what I’m most interested in — a similar tally of benefits and costs.

LIEBERMAN: Sure.

The evolutionary biologist Dan Lieberman.

LIEBERMAN: Just so you know — despite what people sometimes say about me — I view shoes probably much like an economist. There are costs and benefits to that. I don’t see them as being all good or all bad. I’m wearing them right now, for example.

Why is Lieberman so insistent that he’s not anti-shoe? Because he kind of has that reputation. Because in addition to studying the evolutionary history of distance running, he is a distance runner. Who often doesn’t wear shoes.

LIEBERMAN: Sometimes I wear sandals. Sometimes I’ll wear minimal shoes. Sometimes I wear trail shoes and sometimes I’ll go barefoot.  Often, at the end of my run, I’ll take my shoes off and run the last mile or so barefoot.

DUBNER: Describe what it’s like to run barefoot even just a mile.

LIEBERMAN: It’s funny. Most people are afraid of the concept of barefoot running and haven’t tried it. But actually, it’s a delightful experience. You have, by some estimates, the fourth-most innervated part of the body is the sole of the foot. You get lots of information about the world from the sole of your foot. Taking your shoes off can be, as we all know, an intensely pleasurable experience. The reason people are afraid of barefoot running is they think it will hurt. But what almost everybody discovers when they take their shoes off and start running is that you stop running in the same way. Most people, when they’re wearing shoes, land on their heel. You have all this cushioning in the heel that makes it comfortable. Almost everybody, when they take their shoes off and start running on a hard surface, gets off their heel and starts to land on the ball of the foot. That’s called a forefoot strike. And when you run that way, there’s no collision and actually it doesn’t hurt. Barefoot runners don’t mind how hard the surface is. What they care about is how smooth the surface is. Running on a smooth concrete asphalt road is like running on butter. The things that really hurt are gravel, knobbly things, things with a lot of texture, until you have calluses.

There have, of course, been some world-class barefoot runners, even in recent history. There used to be a handful of barefoot placekickers in the N.F.L. Some of the best soccer players in the world grew up playing barefoot. And then of course there was baseball’s Shoeless Joe Jackson, who reportedly played in his socks one day because a new pair of spikes had given him blisters. Dan Lieberman, meanwhile, might best be called a fan of barefootedness rather than an outright advocate. He’s also spent a lot of time thinking about the benefits, and costs, of shoes:

LIEBERMAN: Well, look, I wear shoes most of the time. I’m not so sure that shoes cause that many problems. It’s a little bit more complicated than that. Just putting on a shoe is not like smoking a cigarette. It doesn’t cause you to become unhealthy. Instead, it masks other problems that can lead to poor health.

He knows this how?

LIEBERMAN: Believe me, I’ve looked at thousands of barefoot people’s feet and thousands of shod people’s feet. I’ve seen a lot of horrific feet. I buy a lot of those disinfectant wipes [for] my lab. And I will tell you that I’ll take a barefoot person’s foot over a shod person’s foot any day.

So what has the shoe done to our feet? Coming up on Freakonomics Radio, we get into the details:  

OSTERMAN: In the short term, the problem is the overuse on your knees and your hips.

DAVIS: Our feet get sweaty. They get stinky. But that’s because we keep them in shoes.

OSTERMAN: The long-term effect is it shortens the Achilles tendon and shortens the muscles in the back of the calf.

DAVIS: I wonder what our hands would smell like if we kept them in some device that didn’t let them breathe.

OSTERMAN: There isn’t anybody who wears a six-inch heel into my office who doesn’t know that it is detrimental to their health.

DAVIS: The foot is an amazing structure that is highly underappreciated.

That’s coming up, right after this break.

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Our ancestors went barefoot for many, many years — and happened to be great distance runners. The earliest shoes, made of animal skins or plant matter, were necessarily minimalist. But many modern shoes — whether formal or casual, whether made of natural materials or entirely man-made — are far more constructed. They’ve often got hard soles and substantial heels; heavy padding and cushioning from fore to aft; they’ve got what’s called a “toe box” — which, strangely enough, is often not shaped like our toes, which are wider than the rest of the foot; but the toe box is narrower. All this has led critics to conclude that many shoes are, at the very least, a most unnatural appendage and, worse, are perhaps quite bad for our health. Peter Griffin, from Family Guy, isn’t a fan of the shoe:

Glenn QUAGMIRE in a clip from Family Guy: Peter, would you mind putting on some shoes?

Peter GRIFFIN in a clip from Family Guy: Oh, you mean foot prisons? Yes, I would.

Or, as the late podiatrist William Rossi once wrote: “Natural gait is biomechanically impossible for any shoe-wearing person.”

DAVIS: The foot is an amazing structure that is highly underappreciated.

Irene Davis again, from Harvard Medical School. Her Ph.D., by the way, is in biomechanics.

DAVIS: The foot has 26 bones. It has 33 articulations or joints, each with six degrees of freedom of movement. We have four layers of arch muscles and that complexity is purposeful because the foot has to function as our base of support, a mobile adapter to uneven terrain. It has to be spring-like at times. It has to be rigid at times. When you take that foot and encase it in these very rigid shoes, which I’ll call coffins, the foot then loses its ability to function in the way that it was adapted. I see this in the clinic all the time.

Davis’s Harvard clinic is not to be confused with the Harvard lab run by Dan Lieberman.

LIEBERMAN: We try to understand how, for example, the foot works and then test hypotheses about how feet function, and how variations and foot anatomy affect function, hence performance.

But it is interesting — even heartening, you might say — that Harvard has at least two entirely separate research facilities devoted to exploring — as Davis called it — the “highly underappreciated” foot.

LIEBERMAN: So we will bring into the lab people who have never worn a shoe in their lives and people who wear shoes all the time …

DAVIS: There was a recent study by a group in Brazil and I spent some time with them …

LIEBERMAN: And we’ve looked at how they run and how they walk, how strong their feet are…

DAVIS: … and they actually randomized these women who had knee osteoarthritis into one of two groups.

LIEBERMAN: And we tried to collect some data on injury from them. For example, their knees. We’ve been x-raying people’s knees.

DAVIS: One group stayed in a pair of cushioned shoes and the other group were given this five-dollar — in U.S. dollars — pair of shoes that were highly flexible.  And what they found is, number one, their mechanics were more normal in the minimal shoe.

LIEBERMAN: In those barefoot populations, we find almost no incidents, for example, of people having flat feet. They just don’t exist.

DAVIS: But more importantly to these patients, they had significant reduction in their pain medication and significant improvement in their functional outcomes. That’s just with a pair of minimal shoes.

LIEBERMAN: We look at incidence of musculoskeletal diseases. The evidence appears to be that they have really considerably lower rates of diseases like arthritis. It doesn’t mean that these people don’t have problems, of course they do. But they have fewer problems, it seems, in their feet, their knees, and possibly their hips.

DAVIS: It’s interesting. In the beginning, I really didn’t think footwear mattered. As time went on and my thinking evolved, I started to understand how much footwear impacts our mechanics.

LIEBERMAN: Foot health can affect what’s often called the kinetic chain.

DAVIS: If you take someone who has run barefoot all their life and you put them in a pair of shoes, they’re very likely, when they’re running without shoes, to land on the ball of their foot, because it hurts to land on your heel. But if you put them in a pair of cushioned shoes, they will very likely transition to landing on their heel. That actually creates a cascade of events that happen up the lower extremity and up to the hip.

LIEBERMAN: When you have foot problems, that often causes knee problems, which cause hip problems. We have, for example, an epidemic of osteoarthritis today. One contributing factor to arthritis might be the shoes that we wear. That’s a hypothesis. I don’t have any data on that.

DAVIS: I’m going to suggest that when we put a pair of shoes on that has cushioning like that, it actually creates a mismatch between the way we were adapted to run, which is on the ball of our foot, and the way that we run today. That mismatch results in mechanics that we have shown to be related to injury.

LIEBERMAN: There are a variety of diseases we call mismatch diseases caused by our bodies being poorly or inadequately adapted to novel environments. They lead to problems that range from flat feet all the way up to really serious problems like certain cancers, heart disease and diabetes. When we treat the symptoms of those problems, those mismatch diseases, rather than the causes, we allow the diseases to remain prevalent [and] sometimes become even more severe. It’s a vicious cycle that we create by using cultural methods to not treat the symptoms of mismatch diseases.

DAVIS: Then we’ve got shoe companies who are very much invested in the cushioning, the support and all of the technology that they put into shoes.

LIEBERMAN: What’s happened is the shoes create a problem. Then they create other aspects of the shoe that can solve the problem and tell you that that shoe is better. Mother Nature was a pretty good engineer.

So, do all these shortcomings of the shoe mean that we should consider it, to some degree, a … stupid invention?

DAVIS: As shoes in general, the earliest shoes were not stupid inventions at all. They were there to protect the bottom of our foot, perhaps when it was cold out or we had to go over rough terrain. Just to protect our foot, very much like most of the other clothing we wear. What is stupid is that we have then started to add all of this technology to the shoe. We’re adding cushioning when our muscles can do that cushioning. We’re adding motion control when we can control our feet with the muscles that we have in all of the movements that we have. By doing that we’re actually setting our feet back.

LIEBERMAN: The basic foot we all inherited is probably a pretty good foot. To me the null hypothesis is that that natural barefoot or minimal shoe is probably healthier than a more conventional shoe unless you can prove otherwise.

OSTERMAN: People do things that aren’t necessarily the best thing for them, [but] what looks good with what they’re wearing at the time. Getting over the fashion aspect of it is a very difficult thing for a lot of people.

That is Howard Osterman.

OSTERMAN: And I’m a podiatrist in the Washington D.C. area.

DUBNER: And you happen to treat a couple of sports teams, I understand.

OSTERMAN: Correct. I do the Washington Wizards and the Washington Mystics.

When Osterman says that “getting over the fashion aspect” of shoes is hard for people, you may have thought he was referring to women’s high heels or men’s dress shoes, with their narrow toe boxes. He wasn’t. He was talking about his basketball patients.

OSTERMAN: You would think that they would wear, for their period of time that they’re in the N.B.A. or the W.N.B.A., the most appropriate shoe that they can wear. Bottom line is they want something that is from a company that they want to wear it from, in a style that they want to wear.

DUBNER: I would think that in the N.B.A., foot health is hugely important and that there’s a lot of things that can go wrong.

OSTERMAN: Sure. The players are interesting in that they really have one piece of equipment that they have to buy: that’s their shoes. They really don’t care what their foot structure and shoe company go with. They really will just — for the most part — take what is going to pay them the most.

DUBNER: You’re kidding.

OSTERMAN: For what they can get for free.

DUBNER: Really. I always thought that if you sign a deal then you basically have whoever it is, Nike, Adidas, Puma, custom-make you for your foot at that level? That’s not happening?

OSTERMAN: You know what? The stars have that. But most of the time, I would say we have probably two or three players that that’s for us. There [are] 15 players on the team. You want to know what is my main job working with these basketball teams or with these sports? I basically strip the insides of their shoes and rebuild them with a custom insert.

DUBNER: How many N.B.A. players regularly get pedicures?

OSTERMAN: 90 percent of them.

DUBNER: I’m curious, from your perspective, from the foot’s-eye view, whether the shoe, on balance — whether there are more benefits or more costs?

OSTERMAN: There [are] more benefits. Look, we’ve paved our environment. We work in areas that have hard floors and we do extensive walking. Most of us carry a little extra weight than we theoretically should. Our core strength is not what it was 50 years ago when manual labor was more of an issue. What happens is the shoes can be used for structural stability. They can be used for cushion and shock absorption. They can be used for protection against the elements.

DUBNER: What share, would you say, of the problems that a podiatrist addresses are actually caused by shoes?

OSTERMAN: I wouldn’t necessarily say caused by shoes, I’d say exacerbated by shoes.

DUBNER: What does it say I guess about evolution that we need this fairly complicated piece of add-on gear to walk properly when, in fact, we evolved as a walking animal?

OSTERMAN: Shoes tend to be a fashion statement. There isn’t anybody who wears a six-inch heel into my office who doesn’t know that it isn’t detrimental to their health. When you’re in that higher heel, and anything really over an inch and a half, [it] throws your body forward enough that it puts a lot of stress on the front of the knees. The four muscles, the quadriceps —  that come in the front of the knee that attach just beyond the knee, in the front of the shin — they have to fire constantly to give you some stability. Also, you will arch your back to try to keep you from not leaning forward. That combination puts stress on the knees and the low back. The short-term effect is overuse where the muscles are just not capable of handling it. The long-term is it affects the entire mechanics of how a foot works.

DUBNER: Have you ever had people come to you who want their foot surgically altered so that they will fit the fashionable shoes they want to wear better?

OSTERMAN: Once a week.

DUBNER: You’re kidding.

OSTERMAN: Most of them are just asking, because when you tell them what’s really involved they really don’t want to have it done. You know, because once you start changing joints and re-aligning toes, then you really are throwing the foot into a whole different functional capacity.

DUBNER: It sounds like the shoe causes more changes to our physiology than any other piece of clothing certainly, right?

OSTERMAN: Oh, absolutely. One of the things about these thick-soled, rubber based shoes with good stability is, we were born — both the palms of our hands and the soles of our feet are born with nerve sensors that do what we call proprioception. When your foot hits the ground, it has to register to your brain a certain position, a certain sensation. The problem is when you get these big, thick, clodhopper shoes, what ends up happening is you lose that. There’s a lot of sensitivity that’s lost by going to these more supportive shoes, which is really why the minimalist shoe industry came about.

DUBNER: And you’re generally in favor of them I gather, yes?

OSTERMAN: Yes, absolutely. The problem is, again, we tend to carry too much weight, and we don’t have the mechanics that allow those less-supportive shoes to not create things like heel spurs and plantar fasciitis.

DUBNER: But is part of the problem — when you say we don’t have the mechanics — is that we don’t have the mechanics because we’ve trained ourselves out of having the mechanics by wearing shoes that we wear?

OSTERMAN: That’s a portion of it. Our population is living longer, so there’s more wear and tear on the joints. There’s exercises you can do also to build the musculature. When we send people to physical therapy, they’ll have them either picking up a towel, trying to grip a towel, or picking up marbles, trying to do that.

DUBNER: Should everybody do those exercises on a regular, maybe even prophylactic basis?

OSTERMAN: Absolutely.

DUBNER: But are you doing marble exercises?

OSTERMAN: On occasion.

DUBNER: What’s that mean, on occasion? Come on! How many times in the last month have you picked up marbles with your toes?

OSTERMAN: That would be a zero.

DUBNER: All right, so here’s the question: On the scale of stupid stuff — with 10 being a really bad idea or stupidly executed, and 1 being absolutely awesome and perfectly done — where do you rank the median shoe?

OSTERMAN: I would tell you most of the shoes now are a 3 or a 2. They’ve gotten much, much better.

DUBNER: Really? So we should be grateful.

OSTERMAN: Well, most of the shoe companies do like to sell their shoes. They have really caught the idea that people are wearing different styles. Many of these companies really have taken to better materials and make better shoes.

DUBNER: What would you say that people should look for generally in a shoe, keeping in mind we wear shoes for many different uses and many different occasions?

OSTERMAN: You want something that has a rubber sole, that actually provides some cushion and shock absorption. It needs to have some level of flexibility in the forefoot so that it allows the toes to bend at the level where they bend. A lot of the issues that we see are shoes that either bend midfoot or don’t bend at all, which force the foot to work outside of the general mechanics of [the] way a foot should work. Those are things we’re looking for.

DUBNER: Have you ever looked at videos or maybe seen live people who play music, let’s say, with their feet? People who are missing hands or arms, they learn to play piano or guitar with their feet?

OSTERMAN: Absolutely.

DUBNER: Is that something that you think any of us could be able to do if we habitually used our feet more and obviously had them out of shoes more?

OSTERMAN: The musculature in the feet are very similar to the musculature in the hands. Look at any child who is born without arms and you see what they can do with their feet — as you said, play music, things like that. The dexterity, the neurotransmitters that your brain puts out should just as easily be able to do the toes as they can the hands.

DUBNER: Doesn’t it just seem like there’s this huge wasted resource, that we’re all born with these appendages that have capabilities that we’re not using? Doesn’t that seem like a shame to you?

OSTERMAN: Of course. But it’s a societal issue as much as anything. We went from quadrupeds to bipeds and it changed the whole mechanics of what we needed.

DUBNER: But that said, even though you have that position, you’re not even picking up marbles with your feet. Do you use your feet for anything beyond what I might use my feet for?

OSTERMAN: No, but we have a tendency. I’ll take my shoes off when I’m home. Things like that. You know, we’ll wear sandals in the summer or whatever it ends up being.

DUBNER: But you’re not, like, playing cards with your feet or playing piano with your feet?

OSTERMAN: No, not at all.

DUBNER: All right, let me ask you a flip question: Let’s say that we had evolved — through physiology and culture and so on — to, for some reason, always be wearing heavy gloves on our hands, kind of the equivalent of shoes. But let’s say no shoes on our feet. How atrophied do you believe our hands would be as a result of that?

OSTERMAN: It would be remarkably similar.

Irene Davis agrees we could be doing more with our feet.

DAVIS: The feet actually are very similar in a lot of ways to the anatomy of the hand, in terms of muscles, in terms of nerve supply, in terms of blood supply. Obviously the toes aren’t as long as the fingers, so you don’t have the same kind of dexterity. But I do think that you have the ability to make them more hand-like.

She also thinks we should all spend more time barefoot:

DAVIS: As much as possible. If you’re in an office where people don’t have to see you — because there’s this cultural thing about being barefoot or taking your shoes off. The minute I get into work, I take my shoes off. I treat patients with my shoes off. Take your shoes off at home when you’re walking around the house. Spend some time outside walking barefoot. Yes, as much as possible.

That “cultural thing” about being barefoot — it runs deep, at least in many cultures. Why else would it be illegal to go into a store or a restaurant barefoot, or drive a car? Actually it’s not: there are no federal or state laws against driving barefoot — although if you crash while driving barefoot, you may be blamed more harshly than if you were wearing shoes. As for restaurants and stores — they can legally make their own rules about their customers as long as they’re applied equally to everybody. Davis believes this kind of restriction is less about hygiene than pure social stigma.

DAVIS: I have thought about that a lot and I don’t understand it. Hands go many more places than feet do. Actually, feet are likely cleaner from a bacterial standpoint than hands are. I just think it goes back to culture. It’s something that has evolved in our culture that we should cover our feet. Our feet get sweaty. They get stinky. But that’s because we keep them in shoes. I wonder what our hands would smell like, and would our hands get sweaty if we kept them in some device that didn’t let them breathe?

Irene Davis has a dream. She wants this to be what she calls “the decade of the foot.” I’ve decided to do my small part. I’ve been spending a lot more time barefoot; I’ve even been walking around Manhattan barefoot — well, in my socks, actually, because I’m a bit of a coward. I’ve walked about 10 miles by now; it’s amazing how much more you notice uphills and downhills, and how many different sidewalk surfaces there are. And your leg muscles definitely feel different. I’ve also played some golf barefoot — super fun! And, as Dr. Howard Osterman prescribed, I’ve been picking up marbles with my toes. Nearly every day. And you know what? He’s right — my foot dexterity has increased so much, and so fast! Here, check this out …

[MUSIC: Beata Moon, “Inter-Mez-Zo: Inter,” (from Moon: Piano Works)]

Not bad, huh? All right, that’s not really me. It’s my friend Beata Moon, a composer and pianist. Playing with her hands. But I have learned to turn up the volume with my toes … Next time on Freakonomics Radio:

Barry RITHOLTZ: It’s a tax on smart people who don’t realize their propensity for doing stupid things.

What’s a tax on smart people?

Eugene FAMA: It’s easy to explain. It’s a simple proposition.

What’s a simple proposition?

John BOGLE: It’s Wall Street’s nightmare!

What’s Wall Street’s nightmare?

Barry RITHOLTZ: For how long was the working assumption that the Earth was the center of the universe? We had telescopes, we could see the motions of the planets. It was pretty absurd. We are now in the middle of the Copernican Revolution about the proper way to invest or at least the rational way to invest.

The passive-investing revolution. We’ll hear from Jack Bogle, Gene Fama, Barry Ritholtz and more — that’s next time, on Freakonomics Radio. 

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Freakonomics Radio is produced by WNYC Studios and Dubner Productions. This episode was produced by Shelley Lewis. Our staff also includes Stephanie Tam, Merritt Jacob, Greg Rosalsky, Eliza Lambert, Alison Hockenberry, Emma Morgenstern, Harry Huggins and Brian Gutierrez; and we had help this week from Sam Bair. The music you hear throughout the episode was composed by Luis Guerra. You can subscribe to Freakonomics Radio on Apple Podcasts, Stitcher, or wherever you get your podcasts. You can also find us on Twitter, Facebook, or via e-mail at radio@freakonomics.com.