The Peter Attia Drive - #128 – Irene Davis, Ph.D.： The evolution of the foot, running injuries, and minimalist shoes

00:00:00.000 Hey everyone, welcome to the drive podcast. I'm your host, Peter Atiyah. This podcast,

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00:00:41.720 head over to peteratiyahmd.com forward slash subscribe. Now, without further delay,

00:00:47.740 here's today's episode. I guess this week is Dr. Irene Davis. Irene is a professor of physical

00:00:54.940 medicine and rehabilitation at Harvard Medical School. She's also the founding director of the

00:00:59.520 Spalding National Running Center, one of the premier centers in the United States devoted

00:01:03.320 exclusively to the diagnosis, treatment, and prevention of running injuries and runners of

00:01:07.960 all ages and abilities. Irene holds two bachelor's degrees, one in exercise science from the University

00:01:13.500 of Massachusetts and one in physical therapy from the University of Florida. She then went on to earn

00:01:17.840 her master's degree in biomechanics from the University of Virginia before finally going on to get her PhD

00:01:22.460 in biomechanics from Penn State. In this episode, we talk about a lot of things. And Irene is someone

00:01:28.340 I've been wanting to talk with for about six months, and I was hoping to do it in person so I could

00:01:33.140 actually go to her lab. But alas, COVID turned this into yet another video interview. Nevertheless,

00:01:39.760 the wait was worth it. In this episode, we talk about a number of things. We start with the evolution

00:01:45.740 of running. So when did we stand up as Homo erectus? And then when did we begin to run?

00:01:52.460 How did we run? What was the mechanic of that run? And then what changed about 50 years ago?

00:01:57.780 Because what's really interesting when you think about this is we went from 2 million years ago

00:02:02.020 till about 50 years ago, sort of doing the same thing. And then 50 years ago, something changed.

00:02:08.060 We talk a lot about what that change was and how that change led to where we are today.

00:02:12.720 We had a little nerdy in this episode, but I think the show notes are going to make this

00:02:16.360 really easy to follow. And I go out of my way to stop and have Irene re-explain things and try to

00:02:23.420 re-explain things myself so that people who aren't as familiar with the terminology can understand it.

00:02:27.700 And I think we do a pretty good job of explaining the direction of the forces and just making sure

00:02:33.680 people understand some of the lingo that we use. But that said, the show notes will be very valuable

00:02:38.560 as we especially discuss some of the movement patterns, the gait patterns,

00:02:42.060 the muscles within the foot and the legs, and even things as simple as the different types of

00:02:47.380 strike patterns and what we mean by minimalist shoes. We have a very lengthy discussion about

00:02:52.720 minimalist shoes versus conventional shoes, motion control shoes, cushion control shoes.

00:02:57.800 We do talk a lot about running and walking, but I think a lot of what we talk about

00:03:01.420 goes even beyond that. And we have also a pretty detailed discussion about orthotics,

00:03:06.500 plantar fasciitis, and all of the common injuries that many of you have probably either heard about,

00:03:11.840 know people who have suffered from or have suffered from yourself.

00:03:14.760 So without further delay, please enjoy my conversation with Irene Davis.

00:03:23.860 Irene, thanks so much for making time today. I know you're incredibly busy as evidenced by the

00:03:28.420 fact that you had to change our last meeting in exchange for something that was obviously much

00:03:34.540 more important that we certainly could understand, which was making time to speak with folks at the

00:03:38.860 DOD. And I can imagine how they're very interested in what you do. Tell me a little bit about how you

00:03:44.760 came to be doing what you are doing. For example, what did you study during your PhD?

00:03:50.460 I'm actually going to go back a little bit further. So when I started out in college,

00:03:54.060 I really didn't know what I wanted to do. I honestly wanted to be an FBI agent and wrote a letter to

00:03:59.580 J. Edgar Hoover, who wrote me a letter back that I still have and framed that said that women aren't

00:04:05.640 allowed in the FBI. So at that point, I really didn't know what I wanted to do. So I went to

00:04:10.580 school and started taking classes in exercise science, which led me to wanting to understand

00:04:16.240 how the body works and combine it with medicine. And most people who go into physical therapy often

00:04:22.200 think about either medicine or PT. And I decided to go the PT route, got a degree in physical therapy

00:04:28.500 and worked for a while. But I think I've always had an inquisitive mind. And I kind of knew that I

00:04:34.520 would go back to school for just for additional education and thought that I would probably end

00:04:39.840 up going on for my PhD. So I went on, I did my master's in biomechanics, and then went on to Penn

00:04:45.820 State and did my PhD in biomechanics. The person at Penn State that I went to work with was Dr.

00:04:51.400 Peter Kavanaugh, who is one of the pioneers in running mechanics. And what I thought was really cool was I

00:04:57.720 was able to bring in my medical sort of physical therapy clinical perspective to biomechanics.

00:05:04.400 And marry them. That's really what I did. It's when I started that sort of journey of

00:05:09.620 understanding the relationship between mechanics and injuries. And then I took a position at the

00:05:15.520 University of Delaware to start my career. And on a personal level, was there an injury that you

00:05:21.060 had growing up? Did you know somebody? Were you close to somebody who'd been through the churn of

00:05:26.200 physical therapy, either with or without successful results that kind of created this passion within you?

00:05:31.400 So the physical therapy part, early on, I had a cousin who, in a diving accident, became a

00:05:38.520 quadriplegic. When I watched the physical therapist work with him, I was really inspired. And I actually

00:05:44.500 started my career in spinal cord rehab, but then moved on to, after I started my graduate degrees,

00:05:52.500 I moved into outpatient physical therapy because it was easier to do part-time PT in that kind of

00:05:57.860 environment. And then because of my interest in biomechanics and injuries, really orthopedics was

00:06:03.620 really kind of the better match for me, but really started with that. That's how I kind of got

00:06:08.180 interested. But my interest in biomechanics actually came from the fact that my cousin and other people

00:06:14.740 with quadriplegia have to move 100% of their body with 25% of their muscle power. And it's a

00:06:19.460 biomechanical feat. So you have to learn how to use your body in ways that we don't normally use it.

00:06:24.580 And you have to understand mechanics. And that's really what got me interested in biomechanics.

00:06:29.440 You know, I've been thinking about how I wanted to approach this subject with you.

00:06:32.980 And a lot of times I come into an interview and I have a pretty clear sense of how I want to do that.

00:06:37.140 And I got to be honest with you, I'm still sitting here as we're talking, thinking, God, we could,

00:06:42.300 well, maybe we approach it this way. Maybe we approach it that way. So I'm just going to take a

00:06:45.140 stab at one of the ways I wanted to talk about this with you. And if it goes in a place that's

00:06:49.020 interesting, wonderful, and if not, we'll pivot. But does it make sense to talk about this

00:06:52.600 through an evolutionary lens? Does it make sense to start from the standpoint of what did our

00:06:57.420 ancestors do biomechanically, I don't know, several million years ago that today we do radically

00:07:06.560 different? So in terms of our evolution, having been the driving factor, even more than sort of

00:07:12.280 the environmental change, which I know we're going to talk about the environmental changes later,

00:07:15.740 but just help me understand sort of what the step function changes have been, if any,

00:07:21.200 in the biomechanics of our species.

00:07:23.700 So if you don't mind, I wouldn't mind stepping back one more step and talk about the evolution

00:07:28.100 of my thought that leads to the evolution that you're referring to. So when I started out at the

00:07:34.740 University of Delaware, I had done some work as a physical therapist doing orthotics, and I became

00:07:40.640 the person who taught the orthotics, the foot orthotic component of our program. I was making

00:07:46.400 orthotics, I was doing research in foot orthotics, and really kind of got into the mindset that some

00:07:52.280 people have feet that can't support themselves. And it was interesting, it was kind of like a perfect

00:07:57.020 storm for me, because I was doing research in the area of impacts and injuries. And I realized that

00:08:04.420 when people land on the ball of the foot, and I'm sure we'll talk about this later, the impacts are

00:08:08.700 lower, and people who are barefoot runners tend to run on the ball of their foot. So maybe that's

00:08:13.320 really the way we were meant to run, and footwear can interfere with these things. And so all of

00:08:19.140 these things kind of came together at the same time that the Born to Run book came out. And again,

00:08:24.360 made me start to think it wasn't really the Born to Run book, but again, it kind of made me

00:08:28.260 re-examine my thinking. And it kind of brought me back to when I was a physical therapist in rehab,

00:08:34.240 where we would try to take away as much support and bracing to our patients, even in wheelchairs,

00:08:40.020 a lower back, less lower extremity bracing, so that they would use what they had. And yet,

00:08:45.880 my thinking in terms of feet was completely opposite. And then the other part of it I was

00:08:50.700 thinking about as a physical therapist, we don't brace anything else permanently if you have an

00:08:55.220 orthopedic problem. And yet with the feet, somehow we think someone needs, and I did, thought we needed

00:09:00.900 to have bracing in the foot, I needed to give them orthotics for every pair of shoes they had,

00:09:05.640 and they were going to need those forever. Instead of thinking that these feet actually

00:09:11.120 have these amazing muscles and that they have just as much of an ability to strengthen as my quads and

00:09:16.320 my hamstrings and my biceps. And so it really started to change my thinking then. And then there

00:09:23.680 were papers that came out that showed that when people are placed into shoes that match their foot

00:09:29.920 type, which is really how we got to these motion control and cushion shoes, and I can give you a little

00:09:34.660 history there too when we have a chance. But when you look at the studies that have been done,

00:09:40.040 what they found is that when you match the foot to the shoe, so a motion control shoe for a very

00:09:46.980 low flat foot that's flexible, a cushion shoe for a high arch rigid foot, and a stability shoe for a

00:09:53.820 normal arch, and then you compare that to a group of people who all got the same shoe regardless of

00:10:00.540 their foot type. There was no difference in the injury patterns. This was done by Joe Kanapik

00:10:05.600 in the military. I think something like 7,000 military individuals in different branches of the

00:10:12.020 service. So that started making me think, wait a minute, because I used to prescribe footwear in

00:10:17.520 that way as well. So all of this, along with really kind of meeting Dan Lieberman, who's an evolutionary

00:10:23.880 biologist, who invited me on to the nature paper from 2010, and it was at a time when I was moving

00:10:31.020 from the University of Delaware up to Harvard, which is where he was as well, I really started thinking

00:10:36.020 about the evolution. So when we think about the evolution of our foot, when we went from walking

00:10:42.300 man to running man, so that would be Australopithecus to Homo erectus, we actually started to develop

00:10:50.480 not just changes in our feet, but changes in our body. And there's a great paper by Dan Lieberman

00:10:56.320 and Dennis Bramble, it's Bramble and Lieberman, looking at the changes, the anatomical changes that

00:11:02.740 occurred as we went from walking to running. And what they found is that things like the longitudinal

00:11:10.160 arch, the medial longitudinal arch developed at that point, our joint surfaces got larger because

00:11:17.120 we had higher forces going from walking to running. And so those, those surfaces had to be larger in

00:11:24.640 order to distribute the forces. Our Achilles tendon got longer in order to store the energy, you can

00:11:30.920 walk with a very short Achilles, you don't need to store energy, but for running you do. And so we saw

00:11:36.680 these changes that occurred. And that's really kind of what I have focused on is the changes from walking

00:11:41.680 to running because my interest has been in running, but those changes occurred probably not just simply

00:11:47.080 for running, but they certainly optimized us for running. And they had, I think, 23 markers of

00:11:52.920 endurance running. It's a very fascinating paper. The title of it's called Born to Run, which is

00:11:58.180 interesting. I think that we really evolved to have feet that are very well on their own, well-equipped

00:12:06.820 to be able to walk and run without any kind of support. When you think about the structure of

00:12:12.380 our feet, we've got 26 bones. We have 33 articulations. Those articulations that have

00:12:19.100 six degrees of freedom of motion. The foot is a very complex structure, just like the hand. It's very

00:12:25.480 much like the hand, the anatomy. It also has four layers of arch muscles, four layers of 10 muscles

00:12:31.960 just in the arch. So it allows this foot to have diverse function from being a stable base of

00:12:38.580 support, to being an adapter on uneven terrain, to being a shock attenuator, to being a spring,

00:12:46.180 to being a rigid lever for push off. All of those functions come from the fact that it has that kind

00:12:51.260 of complexity and that kind of beauty. That was really interesting. And there was a lot I'd like

00:12:55.760 to unpack there. You mentioned Dan Lieberman. I saw Dan Lecter for the first time in the summer

00:13:01.800 of 2011. I actually remember it quite well. And I remember being blown away by a lot of things he

00:13:06.440 said. One of the things he said, if I heard him correctly and if I remember correctly, was that

00:13:11.420 over 24 hours, no animal could cover a greater distance than humans. And obviously there were lots

00:13:16.640 of animals that can run faster than humans for short distance, but over 24 hours, we're going to win

00:13:21.360 the day. And again, this was part of the sort of born to run thesis. I want to just go back and make

00:13:27.420 sure I have a couple of things correct. So when did we approximately stand up? How many years ago was

00:13:32.720 that? Oh, now you're testing me. I can tell you when we started to run. We've been running for 2

00:13:39.120 million years. Wow. Okay. That's longer than I would have thought. So 2 million years of, it was

00:13:45.800 essentially a transition from walk to run. Do you have a sense of how much, I mean, again,

00:13:50.300 how much speed did we give up acute speed when we went from, when we stood up? In other words,

00:13:56.860 I'm guessing that when we were on all fours, we could move very quickly over a short period of time,

00:14:02.600 a hundred yards or so, but probably not that quickly over miles. And so standing up gave us

00:14:09.400 that transition, right? We were able to then go slower, potentially over the first few meters,

00:14:16.160 but we could, as Lieberman pointed out, go much greater distances. Is that accurate?

00:14:22.220 Yeah, it probably is accurate, but I think I would really yield to someone like Dan

00:14:26.200 for that kind of information because I wouldn't be confident that I'm giving you accurate information.

00:14:32.300 Well, Dan is definitely someone I'd like to have on this show. I'll save those questions for Dan.

00:14:38.000 Yeah, I think that would be good. But I do know that when we transitioned from walking to running,

00:14:43.580 it was at a time when our brains were getting bigger and we needed meat and we didn't have spears

00:14:50.000 at that time. So we had to really outrun our prey. So we're not very fast runners, but we are

00:14:57.340 good endurance runners. And the reason for that is because we can pant off our heat, whereas these big

00:15:05.280 animals like kudus have their guts sort of slosh up against their diaphragm. And they can only do one

00:15:13.340 breath for every step. And so they aren't able to pant off their heat very well. So basically what

00:15:20.040 we would do is we would carve them out of the herd because we'd be able to follow one and we would

00:15:24.980 just run them to an exhaustion and then club them. So that's why that endurance running was so important

00:15:32.100 for us. So we are probably among the slowest of the animal kingdom when it comes to speed.

00:15:36.360 But as you said, we're very good endurance runners.

00:15:40.120 The other thing you said, Irene, that impressed me was effectively the malleable nature of your

00:15:46.580 thinking. I've met many people who come up in one school of thought, and I'll just use the example

00:15:51.920 you gave, but it's true of doctors. It's true of anybody, which was, hey, we're going to put

00:15:58.000 everybody into orthotics if they have the foot issue. And we're going to try to fit you to the

00:16:02.360 fanciest motion control shoe or cushion control shoe or whatever. And it seems that somehow in

00:16:07.600 the presence of new information, you seemed to very easily be able to let go of that and actually

00:16:13.880 challenge yourself and say, wait a minute. I was very impressed by the way you described it because

00:16:17.560 I'm sitting here saying, how the hell did I not see something so obvious? Which is,

00:16:22.560 and I'm not an orthopedic surgeon, but I certainly am familiar enough with the field to say there's

00:16:26.700 really no long-term use for a brace. I mean, we always want people to strengthen themselves

00:16:33.200 intrinsically rather than rely on extrinsic support. And yet I think up until probably two years ago,

00:16:40.260 I took it on face value that, yeah, orthotics are a great thing if you need them. Never questioning it

00:16:46.200 as you did. I felt the same way about myself at that time. I said to myself, how have I thought this

00:16:51.760 even for this length of time? And I think it really was because of what I had said to you.

00:16:56.460 There was a number of things coming together with my research, with other people's research

00:17:00.260 that started to make sense to me that maybe we aren't supposed to be in this kind of footwear and

00:17:06.480 maybe this kind of footwear changes the way that we run. And maybe we should be trying to strengthen

00:17:11.660 our feet. There were just a lot of things that came together at that time that kind of pushed me

00:17:17.100 into thinking differently. But I really believe that you have to evolve. We have to evolve in our

00:17:22.240 relationships, right? And we have to evolve in our spirituality. We have to evolve in our scientific

00:17:28.000 thinking as well. And I've always believed that. Does it make sense first, in your opinion,

00:17:33.580 to talk about what perfect intrinsic support of the foot looks like and then start to talk about how we

00:17:41.380 got where we got? In other words, do you want to follow this through a time sequence of, okay,

00:17:45.420 so 2 million years ago, we're out there running. Basically, we did that up until when? I mean,

00:17:50.660 when were shoes even brought into the equation? Let me talk about it in that way. So if we look at

00:17:58.240 the fact that we've been running for 2 million years, and we don't know exactly when the first

00:18:03.560 emerged, some of the first footwear that we found were found in the caves in Fort Rock, Oregon,

00:18:10.400 and they were dated to be 10,000 years old, not saying they're the first. But when we looked at

00:18:16.400 them, they basically were made out of sagebrush bark and had a flat surface with straps that kept

00:18:23.080 it on the top of the foot. When you think about that, they're kind of like harachi sandals. The

00:18:28.480 purpose of it is to protect the bottom surface of the foot from the elements. And when you think of

00:18:34.320 other clothing that has developed, short of being fashionistas, it's been to protect us from the

00:18:39.720 cold, the rain, the heat, the snow. And that was really the prime purpose of footwear up until,

00:18:48.000 I'm not exactly sure the dates of when we started to get into some of the high-heeled shoes and some

00:18:52.920 of those things. But in terms of athletic footwear, I'd like to talk about that.

00:18:56.920 Before we do, I just want to go back to this thing, which,

00:18:59.420 why is it that we even needed anything to protect our feet? There's no other animal out there that

00:19:06.840 needs to protect his feet. So a polar bear has enough padding and insulation on the bottom of

00:19:12.740 its feet that it can easily walk through its environment. This is true of every single animal.

00:19:18.340 Why did man not evolve enough protection of the foot to be resistant to scratching,

00:19:25.340 cutting, and extremes of temperature? I think that's probably another really good

00:19:29.380 question for Dan. I hate to pass that on, but we do develop calluses on our feet that help us to

00:19:35.360 protect us from the elements. I don't know what happened that made us, maybe it's a comfort issue

00:19:41.260 where it was just more comfortable. You can walk out on rocks and you've seen people walk across

00:19:47.600 really sharp rocks and be able to do it very lightly, but it's just maybe easier, maybe faster,

00:19:53.140 maybe more comfortable. I mean, that's what I'm thinking is likely to be the reason why we ended up

00:19:58.060 developing footwear. So we basically short-circuited natural selection on that particular element.

00:20:04.200 Perhaps, yeah. And maybe that speaks to all of clothing, actually, aside from maybe some of the

00:20:08.860 social modesty or whatever that came from it, but it might have been that, hey, we could wait another

00:20:13.200 million years and we'll develop really tough feet, but what the hell? We've now got a brain that tells

00:20:18.840 us how to put something on these things that will short-circuit that evolutionary period. Okay.

00:20:23.700 But you know that if you end up going barefoot a lot, that you develop calluses on the bottom of

00:20:30.000 the foot that are protective to the feet. So we do have the ability to develop that protective

00:20:36.240 feature. It's funny that you mentioned Oregon where they discovered the first shoe because,

00:20:41.360 of course, Oregon is the epicenter of another big revolution in shoes vis-a-vis running shoes. So

00:20:46.780 where did running shoes per se, this idea that we're going to put something that's more cushiony,

00:20:53.700 on our feet? It's funny, Ike, I haven't paid much attention to what running looked like

00:20:58.320 200 years ago or 100 years. If you look back at the Olympics at the turn of the last century,

00:21:04.780 what were athletes wearing in the marathon? Were they wearing basically just a flat piece of leather

00:21:10.560 that protected the bottom of their feet? Exactly. And up until probably the 60s, the kind of footwear

00:21:18.480 that we were wearing were really what we would call minimal footwear today. And it basically was

00:21:24.320 something that protected the bottom surface of the foot. There were some developments in terms of spikes

00:21:29.400 for track. And so there has been a development of footwear along that line. But when we're talking

00:21:35.260 about distance running, endurance running, people were running in very flat shoes. And then what happened

00:21:41.440 is we had the running boom. And people got very excited about running. And a lot of people who

00:21:49.200 were not very fit, better than us today, but in their time, not as fit as say runners who were part

00:21:56.600 of a high school team or collegiate track or cross country team, took the sign. Very quickly,

00:22:03.140 they developed some injuries. And some of the first injuries were Achilles problems because

00:22:10.120 people were used to walking around with a little bit of a heel in their shoe, two inch heel, men's

00:22:14.940 shoes got a little bit of a heel. And these shoes were flat to begin with. And Achilles, it doesn't

00:22:20.120 take much. You take out a lift, you know, if you just go down and walk in a flat shoe for a period of

00:22:25.060 time, you can develop an Achilles 10-9 so you don't do it slowly. And so people started to develop

00:22:30.060 some problems with their Achilles. So they started to add a lift in the shoe.

00:22:34.420 Just to explain that for folks who might not be familiar enough with the anatomy,

00:22:37.820 the Achilles is the tendon that's basically joining the bottom of the big muscle of the calf,

00:22:42.800 the gastrocnemius, right around the heel, right? Exactly. It's an extension of the calf muscle

00:22:48.000 and it's the attachment structure to the heel. So the more pointy your toe is relative to your heel

00:22:54.500 or the more your heel is raised, the more compressed that Achilles tendon is. In other words,

00:23:01.340 the less stretched out it is. That's right. That's exactly right.

00:23:05.220 So if you're used to walking around with two to three inches of heel elevation, and then you start

00:23:11.740 running with something that has no elevation, you've got a double whammy, which is one, you're

00:23:17.240 applying a huge stretch to something that hasn't been stretched. And then going back to something you

00:23:22.280 said a few minutes ago, the force of that, the force transfer in that transition from a walking

00:23:29.500 to a running stride multiplies that stretch by some factor that's probably not linear and therefore

00:23:36.560 quite destructive. Exactly. You hit the nail on the head. That was one aspect. So that created this

00:23:42.820 change of adding a little bit of a heel lift to athletic shoes. And this is where the heel

00:23:47.680 to toe drop comes from. The next thing that happened is there were some other injuries that

00:23:53.220 occurred. And I learned about this because I was writing a paper on the reemergence of the minimal

00:23:57.760 shoe. And I wanted to know how we ever got to having a motion control and a cushioning shoe. How did we

00:24:05.840 get these divergent types of footwear? Can you explain what those are? I mean, cushioning to me

00:24:11.060 sounds obvious, but explain it in some detail. So a motion control running shoe is a shoe that

00:24:16.820 actually has a very stiff heel counter and it has material that's stiffer on the inside of the midsole

00:24:24.300 of the shoe that helps to prevent the foot from rolling in. And it also may have some plastic support

00:24:31.120 reinforcements on the inside of the shoe and more arch support to prevent the foot from rolling in.

00:24:37.080 So that would be a motion control shoe. And that's typically designed for people who roll in too

00:24:42.680 much. This was what the original idea was. The other shoe is called a cushioning shoe. And it's

00:24:47.680 for someone typically who has a high arch, doesn't move a lot and needs more cushioning. But what

00:24:53.660 happened is we started to see many more injuries in runners after the running boom. And interestingly,

00:25:00.860 if you look at PubMed and you try to determine when the first, I think the first running injury

00:25:07.620 article was in 1970s, it was in the early 1970s, right? So before then we had lots of people running.

00:25:16.500 And if there was a lot of running injuries, you would have seen literature on it. I'm not saying

00:25:21.440 there weren't any running injuries. Of course there probably were, but it wasn't such a huge issue

00:25:25.660 as it has become. So I really think that it's part of the fact that these people were not trained

00:25:32.040 to cushion the landings. Because when you land, you've got to cushion it and you've got to control

00:25:37.060 it. So if you don't have the muscles and you don't have the motor control to be able to control

00:25:42.860 as your foot comes down so that you can actually attenuate the shock that you get when you land.

00:25:49.660 So you're not using the muscles correctly. You're not landing softly. Then you're going to have

00:25:55.400 injuries that are related to impact and related to too much motion. Does that make sense?

00:26:01.160 It certainly does. I want to make sure I understand what we're calling a running injury,

00:26:05.120 because as I've become more and more obsessed with this topic, what I've come to realize is that

00:26:12.260 if the feet aren't working correctly, the injury can go all the way to the neck. In other words,

00:26:18.140 what I used to assume is if your feet aren't working right, your feet can hurt. But then you

00:26:23.340 realize, well, actually that translates up to the knee and oh, that translates into the hip. Well,

00:26:28.140 actually that translates into the pelvis and the back and the L spine and the T spine and the C spine.

00:26:34.160 And before you know it, you realize if a person isn't connected to the ground correctly,

00:26:39.460 a lot of things go wrong. So when you talk about this wave of running injuries that showed up on PubMed

00:26:46.040 in the early seventies, do you mean specifically foot injuries or what type of injuries are you

00:26:52.120 referring to? I think the very first reference might've been tibial stress fractures. But if

00:26:57.800 you look at the distribution of running injuries, you're right. They can go all the way up to the

00:27:02.940 neck. The majority of them are from the knee down. If you look at the distribution, the knee is the most

00:27:08.920 common site for injuries, the lower leg, the ankle, the foot from the knee down. And the knee is the

00:27:15.340 primary attenuator of shock. So it takes a brunt of the load. You do a, most of your shock attenuation

00:27:22.200 through the knee. What is that load by the way? I mean, I remember knowing this at one point, you know,

00:27:27.300 my undergrad is in engineering and mechanical engineering. So we did a few courses in biomechanical,

00:27:32.340 but I've forgotten so much of it, but I do remember being blown away at what the load was that it was

00:27:38.320 experienced by the knee. So if you took like 175 pound man and he was running, the shock forces

00:27:44.120 felt in the knee were astronomical. They were much higher than what you would expect if you were

00:27:48.780 just thinking about this. The ground reaction force when you land is typically the peak ground

00:27:55.660 reaction force in running is typically about two and a half to three times your body weight.

00:28:00.700 That's the force that your body feels. At the knee itself, it's even higher. So it can be

00:28:07.120 seven times your body weight. So if you're 200 pounds, it could be 1400 pounds.

00:28:12.200 So Nike actually called in three sports podiatrists when they saw all of these injuries that were

00:28:17.920 occurring. I got this information from an individual called Jeff Johnson. And Jeff was

00:28:23.340 with Nike in the early, early days of Nike. And he worked with them. And he's the person that told me

00:28:29.740 that when the injuries started to occur, they brought these sports podiatrists in. But he said that when he

00:28:34.340 was running back in the 50s and 60s in high school and college, he said that nobody was getting injured

00:28:40.560 and that people were running in rubber soles with canvas tops on them. And he said they developed legs

00:28:47.260 of steel. Those were his words, legs of steel. And they weren't having the knee pain and the stress

00:28:53.480 fractures. And of course, that's very anecdotal. But I think it's interesting that speaks to that. But then when the

00:28:58.800 running wound started, we started to see this very quick rise in injuries. So they brought these sports

00:29:03.240 podiatrists in. And what they told them is based on what they were seeing, they felt that the injuries

00:29:08.120 were related to too much impact and too much motion. And it was that. They had no science behind it. And I

00:29:14.200 truly believe that's what they thought clinically. But it was that information that created this divergent

00:29:20.540 motion control and cushioned shoe that we described. What they did is they rather than have the runners

00:29:28.880 adapt to the running, they took the shoe and adapted it to the runner. So instead of making

00:29:36.360 their feet stronger and making them land softer, the runners who are running in shoes that have no

00:29:41.820 cushioning at all, basically like minimal shoes, they adapted it. And the problem with that is that then

00:29:48.360 you start into the cycle where if you give people cushioning, they actually land harder. And that's

00:29:54.300 been shown by a number of different research studies. And when you put a support, the muscles get

00:30:01.240 weaker. And there are lots of studies that show that when you take the support away, take an arch

00:30:07.200 support away, the muscles of the foot get stronger. When you add cushioning, you land harder. There've been a

00:30:13.420 number of studies that have shown that that new Hoka shoe causes people to hit harder.

00:30:19.360 Let's unpack that for a second because the first thing makes a ton of sense. I can really see why

00:30:25.400 removing an arch support will actually allow the foot to become stronger. Take away the extrinsic

00:30:31.880 support, the intrinsic muscles are forced to adapt. Help me understand why the cushioning of the shoe

00:30:39.180 shoe will have the relationship you've described, which is a bit counterintuitive that it would

00:30:44.940 actually increase the force. Assume you mean the force all the way from the ground to foot and then

00:30:51.520 foot to knee. That's exactly right. I'm going to give you an example. So if you are going to hit

00:30:58.160 somebody with your fist, you think you're going to hit them harder if your fist is bare or if you have a

00:31:04.760 padding like a glove. In boxing, you're right. We typically do hit harder with a glove and I think

00:31:10.720 a lot of it has to do with the weight of the glove. You wear a 12 ounce glove, you have more mass that

00:31:15.880 is being thrown. So are you saying it's the mass effect as well of the shoe potentially? I don't think

00:31:21.480 it's just the mass effect. I think it's the fact that you have this protection so you can hit harder

00:31:26.420 and it does attenuate some of the load, but it doesn't attenuate all of the load. What I believe

00:31:32.900 and what's difficult is we don't have a lot of good data pre-cushioned shoes that is high-speed

00:31:39.840 data that looks at foot strike pattern. I think that we evolved to primarily land on the ball of

00:31:45.700 our feet because when you land on your foot barefoot, it's going to hurt. And there was a study done by

00:31:52.960 one of my colleagues looking at the pressure pain threshold of the heel. And what they did is they

00:31:59.760 applied pressure and then they determined when somebody felt pain. And what they found is that

00:32:05.740 when the pressure exceeds the pressure that you have in walking, that's when people start to have

00:32:11.440 pain, which tells us that we naturally, this heel pad was designed, was adapted for attenuating loads

00:32:19.740 of walking. Because you figure we were born to be barefoot. We should be able to do these things

00:32:24.180 barefoot. But running on your heel is very painful, can be very painful because you don't have the

00:32:31.300 cushioning. And there've been other studies that have shown that really is footwear that has changed

00:32:37.000 our mechanics from a forefoot strike to a rear foot strike. Now, it seems to me that maybe somebody's

00:32:43.920 already done this, but you could go back and look at lots of old film of runners going back into the

00:32:50.040 1800s and the early part of the 1900s. And if this argument is correct, you would see that everybody

00:32:55.940 would be a forefoot striker until the advent of cushioned shoes. In other words, this would suggest

00:33:01.700 that heel striking is something that's really only been brought about in the last 50 years. Is that true?

00:33:07.900 It's mostly true. I think that as a barefoot runner, it's been shown that they do vary. So barefoot

00:33:14.000 runners may land on their heel. If you're running in grass, you may have more of a tendency to land on

00:33:18.420 your heel. When you land on your heel, you can stride out more. And so for a given cadence, you can go

00:33:24.500 faster. So it may be advantageous if you're on a soft surface to land on your heel. But when you're on

00:33:30.300 relatively firm surfaces, there's more of a tendency to land on the ball of your foot. And if you look at

00:33:36.720 some of the vases, the prehistoric vases that depict man running, they're always running on the ball of their

00:33:43.600 foot. And if you look at the Boston robot that runs, guess what? He runs on the ball of his foot.

00:33:51.060 I honestly believe that optimally we were adapted to do that. And that's why we have a long Achilles

00:33:56.800 tendon. We have a much bigger calf than we do an anterior. We have much bigger muscle in the back

00:34:02.980 than we do muscle in the front. And when you think about that, one of the most common injuries that

00:34:09.120 runners have when they first start running is this shin splints that they call.

00:34:14.400 Explain to people what a shin splint actually is.

00:34:17.620 It's pain on the front part of the leg. And particularly in the anterior, the muscle in

00:34:23.660 the front part of the leg. And if you're not used to running, landing on your heel and having to use

00:34:29.640 the muscle on the front part of your leg to lower your foot down, you could have an overuse injury for

00:34:35.120 a while until it gets used to it. And so they get sore in the front part of their leg.

00:34:40.960 Let's explain that to people because I think a lot of people won't appreciate that. I think many

00:34:44.720 people might not understand that you have these muscles in the front of your leg, the tibialis

00:34:50.080 anterior, etc. They're in these packed, these tight little fascial compartments. And the point you're

00:34:55.780 making that of course I can see because I'm looking at you is an important one, which is, and so the

00:35:00.860 listener, I just hope they can sort of picture this, as the heel is coming to the ground, they

00:35:05.760 have to eccentrically allow the rest of the foot to come down. And in doing so, you're not using the

00:35:13.500 big muscle in the back of the calf muscle. You have to use that front muscle to control the toes as

00:35:20.920 they come down. And you're saying, look, those muscles are not nearly as big as the muscle in the

00:35:27.020 back. They're going to fatigue long before the muscle in the back. Your point here is, if you just

00:35:33.320 look at the shape of the human lower leg, it's designed to carry more load in the back than in the

00:35:40.260 front. That's correct. Here's another really interesting biomechanical fact. When you land on the ball of

00:35:48.020 your foot, you shift the load from the quadriceps, the muscle in the front of your thigh, and your knee

00:35:56.100 to the ankle and the calf. And when you land on your heel, as a heel striker, you shift the load

00:36:05.000 from the calf to the knee. When you think about the knee being the most common site for injury,

00:36:13.100 then it makes sense. And the knee was not really designed to take those kinds of loads

00:36:18.960 in running repeatedly. But the calf is this big muscle. And what happens is when you land on the

00:36:26.560 ball of your foot, because you have this time in which you're bringing your heel down to the ground,

00:36:32.760 you have that time to attenuate that force. Whereas when you land on your heel, you come in,

00:36:39.260 and it's almost like you get a very distinct impact.

00:36:42.540 In fact, when you look at the force that the ground pushes back up at you, the ground reaction

00:36:50.260 force of a rear foot striker versus a forefoot striker, a rear foot striker has an impact peak

00:36:57.800 followed by a propulsive peak. This impact peak is a very quick rise to peak. A forefoot striker has a

00:37:04.900 very nice, smooth curve that's very gentle. And so this impact peak is associated with a very

00:37:12.920 quick application of force to the body called the load rate.

00:37:17.620 Right. And let's explain why that matters. So if you can picture an x-axis that shows time

00:37:24.120 and a y-axis that shows force, the narrower the force is applied over time,

00:37:32.860 the more problematic it is. And that's what you're describing, which is when you strike

00:37:38.480 with the toe, that force peak is spread out. You can picture a curve over a longer part of the time

00:37:46.120 axis, as opposed to a spike function, which is when you're heel striking, that first transfer of force

00:37:53.520 is an up and down spike before you reach the propulsive phase, which is over a broader

00:37:58.800 application of time. Correct? Absolutely. And the steeper the slope of that first impact peak,

00:38:07.560 the greater the rate of loading. And studies have shown that rates of loading are related to

00:38:16.160 running related injuries. So the softer you land, the less your chance of getting injured.

00:38:23.320 So you've obviously explained a couple of benefits to heel striking. You can take a longer stride.

00:38:29.040 I think it's worth anybody sort of playing with that in their mind. And you can see why you could

00:38:33.620 take a longer stride if you could strike with your heel as opposed to your toe. And you've said that,

00:38:38.960 look, there might be times when you were running on a sandy beach or you're running in the grass

00:38:43.520 where the contact surface is malleable enough that you can get away with it. But so far,

00:38:50.540 what we've learned is for the most part, we've probably had 2 million years of running

00:38:56.100 on a toe strike or forefoot strike pattern. And basically what happened is once people who weren't

00:39:02.860 frankly fit enough to be running due to the other sedentary changes that came with our most recent

00:39:07.960 evolution, coupled with some well-intentioned, but probably ill-informed podiatrists suggested,

00:39:14.840 hey, we've got to lessen the load. We've got to put some cushion here and we've got to

00:39:19.740 make it easier for the Achilles tendon, which has become deconditioned.

00:39:24.060 Basically about 50 years ago, we started building shoes to fit a modern day problem as opposed to

00:39:29.060 taking a modern day problem and deconstructing it to its evolutionary origin. Is that kind of a

00:39:34.580 summary of what you've said?

00:39:36.260 It's exactly right. And that's exactly our approach that we take in our clinic.

00:39:41.160 So when people come to us with injuries and they come to us and many of them come with foot

00:39:47.820 orthotics, habituated to foot orthotics and habituated to standard shoes, our goal, we believe

00:39:54.680 that the closer we are to the way we evolved to move, the less the risk for injury. What you and I

00:40:01.780 are doing right now, we're sitting, it's very unnatural. What we evolved to do was to squat.

00:40:06.840 We really try to get people back into shoes that allow their feet to do what they were adapted to

00:40:14.520 do and to run in a pattern that is closer to our evolutionary legacy.

00:40:19.640 Do you believe that there are some people who shouldn't be running? And I say that not from

00:40:25.100 the standpoint of somebody who is so injured and they have no cartilage left. But I mean, if you took

00:40:29.720 the average teenager who for all intents and purposes still has their body intact, but either

00:40:37.220 they're too overweight or they've spent too much time in a high shoe, meaning a heel to toe ratio

00:40:45.260 that's too great, or there's something about the length of their tibia to their femur that just

00:40:51.340 doesn't seem optimal. In other words, like we say this, that we're born to run, but that's obviously a

00:40:56.780 great general statement. But do you think that there's some nuance to this and that, you know,

00:41:00.240 there's just some people for which running is never going to be a good idea? Or do you think

00:41:04.120 that, no, Peter, truly anybody who still has cartilage left in those joints can be trained to

00:41:09.560 do this thing? Well, I don't believe in a hundred percent of anything. There's always going to be

00:41:15.920 exceptions, you know, that from a medical standpoint as well. But I believe that running is an activity of

00:41:22.400 daily living. People talk about running being a skill. I don't think it is. We learn to run on

00:41:27.620 our own. We're not taught. If you have children, you'll see, you'll watch them go from crawling to

00:41:32.520 walking to running. You don't get out there and you're not training them. Now, there are some

00:41:37.180 runners that could be trained to have better technique, but you know what? You could train

00:41:40.920 walkers to have better technique as well. We evolved to run and it's something that we need for

00:41:46.020 fight or flight. You know, you're going to run away from the boogeyman. You're going to run after your

00:41:49.560 kids. Running is something that is ingrained in us. Having said that, if someone is born with

00:41:56.180 a huge leg length discrepancy that is really going to abnormally load them when they run,

00:42:01.840 that's probably not a good idea. If somebody has some really extreme foot deformities,

00:42:08.360 maybe running isn't the best idea. But I think if we looked at the distribution,

00:42:12.780 the normal distribution of structure, most people can run. And I think that the problem,

00:42:20.940 it starts really, Peter, from when we are children. I would love for you to take a look

00:42:28.280 at a video. There's a trailer on the motivation factor. The motivation factor is a 90 minute

00:42:35.580 documentary about a program at La Sierra High School that was in Carmichael, California.

00:42:42.780 Stan Lepradi, a Marine in 1955, brought a program to La Sierra where he had every single child.

00:42:52.920 He recognized that only 40% of kids are involved in sports. I mean, some kids don't want to,

00:42:58.700 some don't feel they can. So he wanted every single child to be fit. And he took those kids

00:43:05.340 and every single one of them had a PE five days a week, 55 minutes. And they went through a Marine

00:43:12.560 type bootcamp program, but he did it in a way that was highly motivational. So the kids started out in

00:43:18.360 white shorts and then you moved, you had criteria and you were on teams. The white shorts were a team.

00:43:24.240 And when you got to move, everybody cheered you on. You got to the red team. So these kids progressed

00:43:29.700 all the way up. They finally had to add on what they called the Navy blue team and only 21 of probably

00:43:37.300 at least 20,000 people that went through their school because it was a 30 year program and they

00:43:41.920 had 800,000 kids per class. Only 21 made that. This program yielded children and teenagers that were

00:43:51.100 so fit, Peter. When you look at this trailer of the documentary, you're going to be incredibly

00:43:56.360 impressed. They look like they're all military. I think about that. And I think that that's not

00:44:02.020 hard to do. He did it without any real fancy equipment. The kids were doing monkey bars.

00:44:08.000 They were doing pushups. They were doing calisthenics. They were doing the pegboards.

00:44:11.820 They were doing man carries. They did all kinds of things that were building not only strength,

00:44:18.880 but physical literacy. They taught them how to move. Those kids are all going to be able to run.

00:44:24.780 The reason I talk about this, and those kids today are now 55 to probably 79 years old.

00:44:31.840 And we're actually proposing a study to follow them, to look at them now where they are now and

00:44:36.340 compare them to a comparable group that was growing up at that same time.

00:44:41.480 So to see if that sort of critical window of exposure was going to, like an exposure to language

00:44:47.120 or something during a period of time that's critical would stay with them.

00:44:50.060 In the documentary, they all talk about how much this program changed their life. They attribute

00:44:56.700 their success to it. Some of them were in really troubled homes. But aside from that,

00:45:01.580 the physical part of it is that when you see this documentary, you see this video of these kids,

00:45:06.760 every one of them are fit. So I believe, aside from being born with some kind of neurological

00:45:12.620 disability, or certainly those are the ones that I would say probably don't have that same

00:45:17.760 potential. But if you're born with a normally intact neuromuscular system, I think everybody

00:45:23.360 has the ability to look like that. Because I saw it. I saw it in this class. It's amazing.

00:45:28.700 Every single kid. Now their body types are a little bit different, but they were all fit. They were all

00:45:32.960 strong. Every one of them ran. They had to run a mile. Each short level was a different time for their

00:45:38.720 mile. They all ran. So I think running, this is coming back to your question, I think it is innate

00:45:44.620 in us. And I think everyone, you know, who has a pretty normally intact neuromuscular system can run.

00:45:50.380 But to answer your question, should that teenager who's overweight and has been doing video games go

00:45:56.340 out and run? Probably not. You need to get fit to run. These kids are growing up being fit. But if

00:46:03.040 you're not fit, going out and running right away is not the best thing to do. Because I think you need

00:46:07.640 to develop that strength and that motor control. I've had a lot of people who are obese that run

00:46:13.540 and run without pain. If you run on the ball of your foot, you soften the landing. Going from a rear

00:46:20.580 foot to a forefoot strike, so landing on your heel versus your ball of your foot, does not change the

00:46:26.600 peak force. The peak force is the same. It changes that first impact. You remove that impact. And when you

00:46:34.500 think about the landings, you have a thousand foot strikes per mile. You run 20 miles a week,

00:46:40.960 that's 20,000 foot strikes per week. You do that for a year, that's a million foot strikes per foot

00:46:46.560 per year. So that impact, you get that every single time. I think that one of the things that we feel

00:46:53.960 is that by getting off your heels, we actually reduce you, bring you farther away from your injury

00:46:59.960 threshold, which we all have an injury threshold. Our goal is trying to make sure that we keep people

00:47:05.140 as far below it as possible. Do you have a force plate treadmill in your lab?

00:47:10.280 We do. Can you explain to folks what you see when you put, like if I were to come to your lab and we

00:47:17.120 were to experiment and you'd put me in making this up, one day I'm going to run in a minimalist shoe,

00:47:23.180 one day I'm going to run in a hoka, which would be the exact opposite of a minimalist shoe.

00:47:27.000 One day I'm going to heel strike, one day I'm going to forefoot strike. What are the different

00:47:31.380 things you see in that two by two? So minimalist versus maximalist shoe, heel versus toe strike.

00:47:38.320 What does the force plate treadmill show you in terms of like a magnitude effect, especially as we

00:47:45.260 start to now map that out for what you said, which is a million of those a year is not an unheard

00:47:50.440 of amount for someone even running modestly. Well, the first thing I want to ask you is,

00:47:54.120 can I invite you to come and do that? I would happily do that.

00:47:57.900 Okay. I would love it. You're in Boston when I always have a reason to be there. So yeah,

00:48:03.320 I've never run on a force plate treadmill, by the way. So I'd love to know what that's like.

00:48:07.500 So if you're running in a cushioned, a highly cushioned shoe, most likely you're going to be

00:48:11.320 landing on your heel. Which by the way, I used to run in a hoka, so I can relate. I know what that

00:48:16.420 feels like. I know what it's like to heel strike in a hoka.

00:48:18.440 Yeah. So when you heel strike in a hoka compared to heel striking in a conventional regular shoe,

00:48:25.360 normal shoe, a Nike Air Pegasus, let's say, you're likely to have, based on research,

00:48:30.780 higher slopes. It's called the load rate. So a quicker application of force during that first

00:48:38.020 impact peak. If you compare a forfeit strike in regular shoes to a forfeit strike in minimal shoes,

00:48:48.660 you're going to see differences there. The forfeit strike in minimal shoes, your slope will be

00:48:54.740 slightly less than forfeit striking in regular shoes, but that's the vertical direction. And

00:49:00.240 that's all we've been talking about so far. I want to introduce the concept because a force plate

00:49:05.160 will give you the amount of force in the vertical direction, the amount of force you're applying

00:49:10.880 in an anterior, posterior, front to back direction, and the amount of force that you can apply in a

00:49:16.740 medial lateral direction. So what happens is when you forfeit strike in a pair of conventional shoes,

00:49:24.040 you have a tendency to land in more plantar flexion than in minimal shoes, which puts a greater load on

00:49:31.000 the Achilles that we talked about in your calf. And you have a tendency to have a greater force in the

00:49:37.800 anterior, posterior direction. Explain what you're doing with your hand there for people who might not

00:49:42.240 be familiar with that terminology. I'm pointing my toes and I'm coming into the ground, approaching

00:49:48.380 the ground with a very pointed foot. And that tends to push forward on the ground and the ground pushes

00:49:54.100 back at you. So you get this high breaking force. In the medial lateral direction, when you forfeit

00:50:01.260 strike in a pair of regular shoes, you have a tendency to be more on the outside of your foot

00:50:08.480 when you land. This is called inversion. This is your landing on the lateral border of your foot

00:50:14.980 with your medial border up. Right. And I think of that as inversion because the bottoms of your feet

00:50:20.460 now start to point inward to the midline of your body. That's correct. When you land that way,

00:50:26.820 because you're coming down on the outside of your foot, you're kind of pushing outward. You have a

00:50:31.720 greater lateral force that you're applying to the ground. So you have a greater medial by the ground

00:50:38.920 reaction force. So basically what's happening is you increase the force in the medial lateral direction

00:50:45.760 when you are forefoot striking in a pair of regular shoes. When you forefoot strike in a pair of minimal

00:50:52.580 shoes, your toes are less pointed. You tend to be less inverted. So your foot is more level when you land.

00:51:00.080 And so you reduce the forces in the vertical direction, the rates of loading, the slope,

00:51:06.600 you reduce the slope in the anterior posterior direction, and you reduce the slope in the

00:51:10.620 medial lateral direction. So it's the softest landing. When people try to transition to a forefoot

00:51:18.320 strike pattern in a pair of regular shoes, they often come to me with problems with their Achilles,

00:51:24.740 the tendon in the back, and also problems with the tendon of the muscle on the outside of the leg

00:51:31.200 called the perineal tendon. It's a tendon on the outside of the leg. They're so tipped laterally.

00:51:37.640 And they're stretching that out.

00:51:39.720 Exactly. Our recommendation is if you're going to forefoot strike, there's an interaction between

00:51:45.840 footwear and foot strike, and it's important. If you're going to decide you want to transition to

00:51:51.280 a forefoot strike pattern, it should be done in minimal shoes. But if you're going to stay a rear

00:51:56.080 foot striker, make sure you put cushioning under your heel because you're going to need it because

00:52:01.020 you're hitting hard. Now let's get one more idea across, which is there are shoes that have

00:52:08.400 cushioning that have no heel raise. I'm blanking on a brand. I have a friend who wears them.

00:52:13.940 And I think it starts with an A, but I could be wrong, but it's got about a three quarter inch

00:52:18.720 sole, but it's the same at the front and the back. So it has zero elevation of the heel,

00:52:24.380 but it has some cushioning. And of course we wouldn't consider that a minimalist shoe, would we?

00:52:29.100 You might be thinking of the Topaz.

00:52:31.300 It's not. I could look it up, but I guess the point is when you say minimalist, we're talking

00:52:35.900 really about two features, no elevation of heel and no cushion or support, correct?

00:52:41.680 Yes. When I talk about minimal, I'm talking about a shoe you can roll up and put in your pocket.

00:52:48.100 Okay. How many brands are there of those shoes? I wear a brand called Zero. There are another

00:52:53.520 couple of brands out there.

00:52:55.300 There are. There's many, I think, but some of the big brands that you think about

00:52:59.500 are Vivo Barefoot.

00:53:01.660 Yep. That's the one I was thinking of. They seem to make a pretty nice looking product.

00:53:05.400 Yep. And then there's Innovate.

00:53:07.660 Okay. So is Innovate a true minimalist? I mean, I love Innovate and I have them,

00:53:11.680 but I've sort of migrated over to the zero because it has a wider toe box. And I'm also,

00:53:18.300 one of the things I've been working very hard on, which I'd also like to come back to. So I'll just

00:53:21.860 mention it now and we'll park it, is spreading my toes. So at the outset, when you were describing

00:53:28.200 the anatomy of the foot, I was using my hand to pretend it was a foot. You saw me doing that and

00:53:34.440 you made the comment just like the hand. And I, through a colleague had an epiphany a year ago,

00:53:40.140 which is, can you imagine how unhelpful your hands would be if they were shoved into tight gloves

00:53:46.820 most of the time, as opposed to being able to spread apart. And since that time, I've been working

00:53:52.520 greatly to sort of enhance the spread of my toes so that I could actually use these feet the way I can

00:53:58.860 use my hands. And so for that reason, that's when I went from the Innovate to the zero was to be able

00:54:03.780 to actually get those toes across. But you're saying the Innovate is still a minimalist shoe

00:54:08.920 because it meets the criteria that it can be rolled up into a ball. Some of these minimal companies

00:54:13.560 actually have shoes that have some midsole. So as long as the shoe has no midsole, so some of them have

00:54:21.320 real true minimal models and then some that add a little bit of cushioning into them.

00:54:26.260 So what I'm saying is if it's a model that has no cushioning, has no arch support,

00:54:32.780 has a flexible heel counter and flexible upper, and you can roll it up, it's a minimal shoe.

00:54:38.480 Now, what happened after the Vibram lawsuit, which by the way, was not about injury, but about false

00:54:46.780 reporting of increased muscle size with the use of the shoe.

00:54:51.280 I'm not aware of the lawsuit.

00:54:52.880 There was a lawsuit that came out against Vibram, and it was basically about false advertising.

00:55:00.600 Although a lot of people, because when Vibram shoes first came out, a lot of people thought

00:55:05.860 you could just put these shoes on and run. And we need to talk at some point about transitioning,

00:55:10.700 but there were some reports of injuries with them. And I say, it's just like if you were to go to the gym

00:55:17.540 and lift a hundred pounds when you never lift and gotten injured, you wouldn't say, don't ever do

00:55:21.480 that again. You'd say, don't do it that way. Well, what happened with this is it really turned

00:55:26.780 people against the minimal shoe. And a lot of people think that the lawsuit against Vibram was

00:55:32.880 about injury because people, there were some reported injuries in the literature. It was about

00:55:37.980 the fact that the Nike free shoe, which was the very first barefoot type shoe, wasn't really quite

00:55:43.820 truly barefoot or minimal, had shown that you increase muscle size when you take away the support

00:55:49.700 in the arch. And since the Vibram shoe took away the support of the arch, they were advertising this

00:55:54.480 could strengthen your feet. That's what happened. So what it did is a lot of the shoe companies sort

00:56:00.440 of pulled back and started adding a little bit more to their minimal shoes. I think New Balance

00:56:07.340 had a New Balance Minimus that had no midsole. Minimus Trail, I think had no midsole. And then

00:56:13.420 they started to put a little bit of a midsole in there because I think that they thought that that

00:56:18.380 was what we needed to do to try to prevent injury. But I call those shoes partial minimal shoes

00:56:24.700 because some of them have a little bit of a heel to toe drop. Some of them have a little bit of arch

00:56:31.080 support. Some of them have some cushioning and they have various degrees. The Nike free, for example,

00:56:37.360 was the very first shoe. There was somebody at Nike, his name was Jeff Pichotta, and he was tasked

00:56:43.580 with studying barefoot running and coming up with a shoe that mimicked it. That's why it has all those

00:56:49.600 flex grooves on the bottom of the sole. So it can be very flexible. He took away the arch support.

00:56:55.980 He took away the stiff heel counter. I mean, that's a pretty thick shoe, isn't it though?

00:57:00.580 An inch of cushioning, right? Yes. His plan was to have a Nike, maybe zero to 10.

00:57:08.240 Like no cushion all the way up to full cushion. Barefoot all the way up to having cushioning.

00:57:13.940 And they started out, I think, with the 5.0 and they did do a 3.0 and a 7.0. I don't know if

00:57:19.080 you remember these. And they were either more or less cushioned. But the problem with the minimal

00:57:23.860 shoes are that the studies that have been done have demonstrated that when people run in a

00:57:29.660 partial minimal shoe, they run closer to running in a regular shoe than barefoot.

00:57:35.400 In which case, it defeats the purpose because they're still heel striking, but now they have

00:57:39.380 less cushion. Exactly. And a study that was done looking at a regular shoe, partial minimal shoe,

00:57:46.500 and a minimal shoe over the course of a training cycle of 12 weeks, the partial minimal shoe had

00:57:52.600 twice the injuries as the minimal shoe. And the authors suggest that it may be, and they didn't

00:57:57.680 look at biomechanics, but it may be because the partial minimal shoe, they still were heel striking,

00:58:03.020 but now you have less cushioning. Which is why I say, if you're going to land on your heel,

00:58:07.080 put cushioning under it. I'm not going to try to convince people to run a certain way. When

00:58:10.980 people come to me with injuries, then we have a conversation about why we might want to change

00:58:17.000 foot strike. But if people are out there and they're happy, I'm happy for them. I just say,

00:58:21.700 you need to put cushioning under there and you need to change those shoes every three to 500 miles.

00:58:27.360 I don't know if you know, the shoes that you have, the zero shoes are guaranteed for 5,000 miles.

00:58:32.940 I did not know that. And I don't know if my wife will let me keep any one pair for that long.

00:58:38.300 I know. I know. They're growing on her. She initially called them my clown shoes. She was so

00:58:45.160 unimpressed with them. But then I got her three paired. They've just evolved in terms of their

00:58:50.620 fanciness now. So she likes them a little bit more. Yeah. They're a little nicer.

00:58:54.780 You brought up something that I want to go a little deeper into. So I made this mistake

00:58:58.960 before with a friend, which was they were wearing orthotics. This was after I'd sort of

00:59:05.900 bought into the thesis that, hey, you don't want to be using orthotics indefinitely. You want to

00:59:11.120 regain the strength that is intrinsic to your own foot. And I sort of tried to help him wean off the

00:59:18.220 orthotics, but I think I did it too quickly and it ended up kind of causing him pain. So walk us

00:59:25.360 through how you handle a patient. So patient comes to you. I'll just make up an example, but feel free to

00:59:31.760 come up with a different one if this isn't instructive. But this is someone who's athletic,

00:59:36.780 a former athlete even, a former runner for that matter, who goes on to perhaps they stop running

00:59:43.420 and they come back to running. They develop very bad plantar fasciitis. They see a podiatrist who

00:59:48.340 says the diagnosis is low arches or high arches or some arches, and they need to be in a stiff

00:59:54.460 orthotic. And now they're in an orthotic. And now they come to you and they say, God, I'd really love to

00:59:59.020 run again. But this plantar fasciitis just won't quit. What can you do for me, Dr. Davis?

01:00:05.160 I always try to educate my patients because they need to buy into this. Our approach is 180 degrees

01:00:12.200 from the approach that they've been given. And I don't want to diss someone else. I just want to say

01:00:16.560 we've got a different approach. And our approach is rather than adapt to you, we want you to adapt

01:00:22.640 to running. And so that requires you using your muscles and your body in a different way.

01:00:27.380 And I give them the example of a neck brace. This is always really very illustrative for them.

01:00:33.820 So if you put someone in a neck brace for life, what's going to happen to your neck muscles?

01:00:38.660 And they say, well, they're going to get weak and I'm not going to be able to hold my head up.

01:00:42.040 So if I give you a foot orthotic for life, what's going to happen to those muscles?

01:00:46.360 I think we all think that the arch is going to fall and the arch doesn't fall. The arch actually

01:00:50.860 gets stronger. So when you use that kind of analogy, a light bulb goes on like, wow, yeah.

01:00:56.180 Yeah. They don't realize they have 10 muscles in their arch. So I go through that anatomy with

01:01:00.380 them. I'll show them a picture of it. And I go, you've got 10 muscles and four layers in your

01:01:04.820 arch of your foot. They can get stronger unless you're paralyzed. I don't think you're paralyzed,

01:01:08.680 right? No. So what we're going to do is we're going to slowly wean you from those orthotics. And at

01:01:15.080 the same time, we're going to be giving you exercises to strengthen your feet so that it can start to

01:01:20.040 take on the load that it's supposed to take off. So what we do is we slowly wean them and we usually

01:01:26.600 wean them out in the same way I used to wean people in, which is I'll say, take them out for an hour in

01:01:31.580 the morning, but keep them with you. You don't want to take them out and go cold turkey. And it depends

01:01:36.340 again on how much they're doing. If they're walking to work and they're going three miles, you don't want

01:01:41.540 that to be the hour that they take them out. Maybe walk a half a mile without them or a mile without

01:01:47.160 them. And then just slowly take them out and use your body to judge. If your feet are feeling sore,

01:01:52.840 put them back in. And we never take them away from them. I mean, they always can have them.

01:01:58.000 So if they decide at some point they want to go back to most people come to us wanting to get out

01:02:02.900 of them because they're a pain. They're expensive and they've got to replace them at times and they

01:02:07.600 stink and they just don't like the idea of it. A lot of people don't. So that's how we wean them out.

01:02:12.920 At the same time, we are strengthening their feet. And we also, once somebody has weaned out of them

01:02:21.740 and they're able to walk comfortably without their orthotics in their regular shoes, then we put them

01:02:27.740 in a pair of minimal shoes like the ones you have. There are lots of different brands. We have three

01:02:32.820 brands in our office where they can try them on and decide what they like. Some people's feet are

01:02:37.860 narrower. So what are the three brands you like people to try?

01:02:40.920 I want to kind of be shoe agnostic because I love them all.

01:02:44.300 Yeah, yeah.

01:02:44.880 The three we have just because people have given them to us really are the Innovates,

01:02:48.620 the Vivo, Barefoots, and the Xero. So it's the ones that people have donated the shoes to us,

01:02:52.800 I think to their advantage because those are the ones people are going to try. But there are others

01:02:57.600 as well. And so we get them walking in the minimal shoes because we published a study that showed

01:03:03.600 that simply walking in minimal shoes is as efficacious, as effective as a foot strengthening

01:03:12.220 program. So we had three groups of people in this study. Sarah Ridge from BYU was the first author.

01:03:18.900 One group walked around in their regular shoes. Another group slowly progressed their walking steps

01:03:24.560 in minimal shoes. And the third group went through our foot core program over eight weeks. And the foot

01:03:30.660 core group and the minimal shoe group had almost the same amount of strengthening. Foot core group

01:03:36.140 had a little bit more strengthening, but it's very powerful when you think just putting a pair of shoes

01:03:40.740 on is going to strengthen your feet. And so we have them do that right from the get-go.

01:03:47.520 If someone comes to us with plantar fasciitis, it's not right from the get-go. And in orthotics,

01:03:51.440 we take that slowly because it's important that they develop. They've got to give the foot time to adapt

01:03:56.700 to not having the orthotic. So what does that look like? Let's go through that in some detail.

01:04:02.440 Yeah. So it depends on the person and how long they've been in the shoes and how weak their feet

01:04:07.520 are. So what we do is we just try to slowly wean them out over the course of maybe two to three weeks

01:04:13.200 of weaning them out. And that's sort of the protocol you described earlier, which was

01:04:17.020 maybe just take it off for an hour in the morning as you walk around the house.

01:04:20.900 And then an hour in the midday and an hour at night, maybe something like that.

01:04:24.340 Yeah. Got it. Okay. So the first goal of therapy for that patient is if I could get you for a day

01:04:31.000 to just through your activities of daily living, not require full arch support, that's a win. That's

01:04:38.040 step one. That's step one. That's right. And then we build their foot strength and we get them to wear

01:04:43.020 the minimal shoes just walking. And our program, when we transition someone from regular shoes,

01:04:49.560 even if they're not in orthotics to a minimal shoe and forefoot strike requires what we call our

01:04:55.160 pre-gate program. So that program can be anywhere from one to three months, depending on the person

01:05:01.740 and their age, the older you are, the more time it takes. Typically we're a little less plastic as we

01:05:06.320 age, but it's a program in which we do foot strengthening. We're also addressing other issues.

01:05:12.320 It's not just foot problems, but foot, hip, knee. We're working on functional activities,

01:05:17.580 teaching them how to use those foot intrinsic muscles when they're moving. So it's not enough

01:05:23.640 just to strengthen. You've actually got to teach people how to engage them during the activity.

01:05:29.400 And then we do a lot of off the treadmill kinds of activities like hopping and lunging and plyometrics

01:05:36.480 and jump roping and all kinds of things that helped get them to move dynamically, but not run.

01:05:42.220 These are components of running. And once they've met certain criteria, which can take anywhere from

01:05:47.180 one to three months, depending on the person and what kind of pain they're in, then we put them on

01:05:51.540 the treadmill and we start to do the retraining. When somebody is wanting to transition to minimal

01:05:57.020 shoes, even if they're completely healthy, I can't emphasize enough that it's not just putting a new

01:06:04.540 pair of shoes on. It's changing the way that you even walk and it's putting greater demands on your

01:06:10.280 foot and your ankle. And so you need to give yourself time. And so you need to walk and make

01:06:15.400 sure you can walk for maybe 30 minutes briskly, and then start to interject some running slowly.

01:06:21.940 Because if you don't, you're going to load the foot faster than it's ready. And you can create

01:06:28.520 problems like plantar fasciitis or worse of a metatarsal stress fracture. The bones of the foot,

01:06:34.360 every bone, your tibia, those are really protected by muscle. So when you have one of the long bones

01:06:41.280 of your foot, the muscles on the bottom of your foot and the muscles on the top of your foot are

01:06:45.480 balanced so that the strain in the metatarsal is minimized. But if you have an imbalance in that

01:06:52.740 muscle strength, then you're going to get additional strain on these metatarsals, which can lead

01:06:57.760 repetitively to a stress fracture. So it's really important that they strengthen.

01:07:03.320 You know, Irene, I've looked at more CT scans and MRI scans of people than I can ever possibly

01:07:10.120 count. And let's just say you're looking through the trunk or the legs. The difference between a

01:07:17.320 muscular person who's super fit and someone who's never exercised in their life is so apparent at the

01:07:24.120 level of every muscle. There's the obvious muscles. You look at the quadriceps. You look at the

01:07:29.140 quadriceps of a muscular person. I mean, you can see those four muscles. They are huge.

01:07:35.220 But even at the level of the rectus abdominis muscles, you take a look at a person who's never

01:07:40.800 done a core exercise or a crunch in their life, and they barely have like half a centimeter thick

01:07:47.000 of a rectus abdominis muscle. And then you look at somebody who's incredibly fit all around,

01:07:52.000 you see a rectus abdominis muscle that's easily an inch thick. I've never bothered to look at

01:07:59.440 the MRI of a foot for the same thing. But hearing you talk about this makes me wonder if you look at

01:08:07.620 a person who runs in a minimalist shoe, who's been doing it forever, who's got these amazingly

01:08:13.860 intrinsically powerful feet. And then you look at somebody who's using a highly supported shoe.

01:08:20.120 If I show you those two CT scans or MRI scans, just on the basis of the musculature, can you

01:08:27.320 see a clear difference? I don't look at those very often, just because I'm more on the rehab side of

01:08:34.800 things. I know that research shows, it's been done with ultrasound, that when people run in minimal

01:08:41.260 shoes, the volume, we've done a study looking at volume of the foot intrinsic muscles, as well as

01:08:47.140 the cross-sectional area of each muscle gets bigger, significantly bigger. So I would say likely, yes,

01:08:54.060 you would be able to notice it. I know that those numbers definitely increase. What I also know is

01:09:00.680 there was a study recently done that was presented in a meeting, it hasn't quite, it's in review right

01:09:05.760 now, that took healthy feet and put them in a pair of orthotics for 12 weeks. And then they had a

01:09:12.880 control group that just weren't a pair of shoes. Over 12 weeks, they measured that baseline. And at

01:09:18.380 the end of that time period, the intrinsic muscles size reduced between 10 and 17%, 10 and 17%

01:09:26.420 reduction. And the other group, there was no change at all. We wouldn't expect it. What does that tell you?

01:09:31.840 We know that when you take away the support, the muscles get bigger, but it makes sense, but no one

01:09:36.020 has actually shown this, that when you actually add support, those muscles get smaller. It makes

01:09:40.640 perfect sense. And yet, we don't think about that. We don't even think about the importance of those

01:09:47.520 foot muscles. There was a recent clinical guidelines in the Physical Therapy Journal, looking at clinical

01:09:53.480 guidelines for treating plantar fasciitis. And they have all kinds of recommendations, ultrasound,

01:10:00.080 orthotics, ice, stretching, everything but strengthening. And if you look at the clinical

01:10:08.260 guidelines for something like ankle sprain, or knee injury, or shoulder injury, they all include

01:10:13.940 strengthening. And that's my own profession. That highlights the lack of appreciation for the muscles

01:10:20.140 in the foot. And they're very, very important.

01:10:23.620 So how many podiatrists would agree with your approach versus disagree with your approach? And is

01:10:29.020 there a position statement taken by the field as a whole on this? Because I've been to podiatrists

01:10:34.620 myself three times in my entire life. And every time I did, I walked out with a set of orthotics.

01:10:42.340 Now, it could be that that's just a bad sample size, but that would lead me to believe that the

01:10:48.400 entire field of orthotics is built around that. And I could be very skeptical and say that it has to do

01:10:53.520 with reimbursement, and they're making money on the orthotics, and all sorts of things.

01:10:57.160 I'll refrain from that speculation. But where does the field as a whole sit in relation to what

01:11:02.880 we're discussing now? So when I first started talking about this, I used to present at the

01:11:09.320 foot orthotic meetings with a group of podiatrists. So when I started to change, I think they were very

01:11:15.540 surprised. And I have debated on stage a very good friend of mine, colleague, who is very dug in

01:11:24.600 about his dogma and orthotics. And I think it's because they think it's working. I have to believe

01:11:31.220 that he thinks that this is the right thing to do. But we went back and forth. Now, this was probably,

01:11:36.960 I don't know, eight years ago now. I don't know what he's thinking now. But I can tell you that more

01:11:42.240 and more podiatrists are telling me that now they think about orthotics as more of a temporary thing.

01:11:47.960 So I think we're moving in that direction. There are some podiatrists, there's one that I have been

01:11:53.820 in touch with recently, who is very much on the barefoot running and all of that. And he doesn't

01:11:58.920 prescribe orthotics at all, which is really unusual. I went down to Australia, I was invited down. And

01:12:05.880 again, this was probably about six, seven, eight years ago, again, same time period, probably,

01:12:10.080 they asked me to give a talk on barefoot running. I thought, gosh, do they really want to hear this?

01:12:15.580 Because it was a big podiatric group, I found that a lot of them were very open to the idea of

01:12:21.980 treating people with exercise and not orthotics. So it could be somewhat regional. And these were

01:12:28.580 also younger podiatrists. So the ones that are coming up are thinking differently.

01:12:33.360 My husband tells me, because I am a very impatient person. And he said to me, Irene, the way that you

01:12:38.300 change things, the way that you bend bamboo is a little at a time, you add some water and you bend it,

01:12:43.480 things are going to be slow to change, and you just have to keep at it. So my goal is to get people

01:12:50.600 back into minimal shoes from day one, because I think they're important for kids. I don't think we

01:12:58.900 should be putting kids into really structured shoes, let their feet develop. I think they're

01:13:02.780 important for adults. I also think they're very important in the aging. When you have a shoe that

01:13:09.420 allows your foot to be closer to the ground, you're more stable, that allows the muscles to act.

01:13:15.860 Because one of the things that happens with aging, as you start to lose muscle power, you lose it

01:13:20.800 in your feet and lower extremities first. It goes from the feet up. So if you can do something to help

01:13:26.620 to preserve that strength, that's a good thing. I think it's really important. We're in the process

01:13:31.560 right now. A group of us are writing a paper about the minimal shoe across the lifespan,

01:13:35.700 because I think it's not just about athletics. It's about getting people into shoes that let their

01:13:41.160 feet do what they're supposed to do. I've really come to believe that as well, Irene. I got my little

01:13:46.280 guys some zeros last year because I sort of realized we were putting them into an ideal world. I'd love

01:13:53.120 for them to run around barefoot for the reasons you suggest, but look, you want to protect the bottom

01:13:56.680 of their feet. The concrete gets too hot. Okay, fine. But putting the zeros on them and hopefully they'll

01:14:02.720 skip some of the stuff that the rest of us did. And to your point, I think as people age, you know,

01:14:06.880 the analogy I like to think about when I talk about feet is the tires on a race car. You watch

01:14:12.380 something like Formula One, right? Which is the pinnacle of motorsport. And what you have to

01:14:17.020 remember is all of that power, that thousand horsepower engine, that million dollar car has only four

01:14:24.680 points of contact with the road and they're called tires. Every bit of force generation in the AP

01:14:31.740 direction and in the medial lateral direction is transmitted through the drivetrain, through the

01:14:37.600 tires to the road, full stop. That's it. So now imagine how much you could de-engineer tires to

01:14:46.400 distance them from the road, how much you could create lateral instability, how much you could remove

01:14:53.920 grip from them. And I think about that through the lens of our foot. If you cram your foot into a

01:14:59.960 narrow little box and remove it from the surface of the road, it's sort of like making your tire

01:15:06.480 have less grip, more slip angle, and less lateral stability. None of those things are desirable in a

01:15:13.840 tire. I think if you just sort of think about the importance of connecting to the ground, it does start

01:15:20.200 to become pretty obvious. And I actually like the way you're thinking about it, which is let's not

01:15:24.880 shoehorn everyone into this box. If somebody comes along and says, look, I'll never be able to give

01:15:29.600 up heel striking. Well, that's not a person that should be going to a minimalist shoe. That's fine.

01:15:35.140 Let's hope that everything else is going okay. I do want to ask you like, what is a good reference

01:15:39.360 for somebody? Let's say there's somebody listening to this now who's wearing a maximalist shoe, who's

01:15:44.160 heel striking and either does or doesn't have injury, but says, you know, I want to start thinking

01:15:49.300 about this transition. What are the references to learn how to forefoot strike? Is this just something

01:15:54.760 you just go out and do and start concentrating on? To be honest with you, I know that there are people

01:16:00.140 have written books about it. There are courses on pose and chi running. I guess I believe that it is

01:16:08.160 our, if you take your shoes off, it's a natural way you want to run. Now you might still land on your

01:16:14.300 heel for a little while because you're used to it. But it's interesting. When I was in college,

01:16:19.700 I was running maybe about 20 miles a week just to stay fit. And I ended up with thinking, I can't

01:16:25.120 remember what the injury was, but every time I stopped, it would go away. And then when I'd start

01:16:28.280 running, it came back. So I gave up running. I did a lot of inline skating, a ton of inline skating,

01:16:33.240 did some marathon races and stuff in it. When Born to Run came out and I met Chris McDougal because Chris

01:16:38.560 came down to, he lived in Lancaster, lives in Lancaster now. And he came down to the University of

01:16:44.000 Delaware because he was doing a story for, I think it was the Times. And he wanted me to run him on

01:16:50.180 the treadmill and run him barefoot and that kind of thing. So we got talking and he said to me,

01:16:54.520 you know, I haven't run in so long and I think I'd really like to run again. Should I get those

01:16:59.120 Vibram shoes? And he said, you know what? Start barefoot. Just start barefoot and your feet will

01:17:03.760 teach you. And I did. That's what I did. I started running again barefoot. My feet did teach me.

01:17:09.400 It's like, you don't need to be taught to walk. Now, if somebody has really bad posture,

01:17:15.300 you have all kinds of postures and walking as well. We can improve walking. I'm not saying that

01:17:19.900 you can't improve the technique of someone in running, but I feel like sometimes people overthink

01:17:24.920 it. Get people in that do these really strange things. Like they're kicking their butt and they're

01:17:30.060 not running fast. They're running slow, but they're kicking their butt. Like why are you kicking your

01:17:34.840 feet of someone? Well, that, you know, I was told to do that. So it seems like maybe just going to

01:17:39.420 grass, going to a forgiving environment and running barefoot and doing it for very short periods of

01:17:44.760 time. Instead of doing like a long run, say, look, I'm going to go and run a few hundred yards,

01:17:50.860 stop, regroup. I'll give you an example. I learned to swim as an adult. I guess we could sit here and

01:17:56.160 debate whether swimming is innate to our species. It seems there's probably a very early window in which

01:18:01.760 if you're exposed to swimming, when you're, you know, a few months old, it tends to come naturally,

01:18:05.860 but certainly anyone who's watched a five-year-old who's never a swim, you realize it doesn't look

01:18:10.820 too innate, but nevertheless, I'm 31 when I'm learning to swim. And the only way I could really

01:18:17.200 do it was to understand the technique and do it in very short bursts with lots of rest so that my

01:18:24.500 technique wouldn't deteriorate, which basically amounted to doing a lot of drills and never really

01:18:29.660 swimming more than 50 yards or 50 meters at a time until I slowly learned how to piece those

01:18:35.920 together. And I haven't read Chi Running. My wife actually has it because Terry Laughlin, who's the

01:18:42.160 guy that taught me how to swim, he's no longer alive, but Terry created a program called Total

01:18:48.400 Immersion for Swimming. He was very good friends with, I forget, is it Danny? What's the guy who wrote

01:18:53.540 Chi Running? Oh yeah, I've met him. Danny, yeah, I can't remember Danny's last name. I can't recall,

01:18:59.100 but Terry and Danny were friends. And when Terry knew that my wife was a runner, he got her

01:19:04.340 connected. And I guess I should go back and read the book. I'm very curious now about what the methods

01:19:09.760 are, but it really is whether you decide you never want to run for the sake of running or whether you

01:19:16.340 decide, I actually do want to run. I want to use running as a form of my exercise. I just don't think

01:19:22.320 you can make a strong enough case for why it's imperative that we learn to use our feet better.

01:19:26.600 That's sort of my thinking on this subject matter is the minimalist shoe becomes a vehicle through

01:19:31.820 which we learn to acquire the contact of our feet to the ground. And if you want to run,

01:19:37.060 that's essential. Yeah, I agree. I want to go back to something that you said about when you start

01:19:42.200 running. This is another thing I asked Chris. First of all, I asked him, should I wear the vibrancy

01:19:47.300 goes? No, you really need to go barefoot so you get all the sensory input. And I said, you know,

01:19:51.760 I like to paint my toes. I go, Chris, I don't want to get calluses. He goes, honey, the world is your

01:19:56.640 pumice stone. But he told me don't start in grass. And the reason for that is that when you start in

01:20:03.100 grass, well, first of all, grass is more dangerous. I've never cut my foot. I have burned my foot on

01:20:08.360 hot pavement at times because I wasn't smart enough not to run when it was really hot. But the problem

01:20:14.400 with running grass is, first of all, you can't see what's there. I'd be a little nervous running

01:20:17.780 barefoot in grass. Honestly, I've cut my foot in the sand, sharp shells and things like that.

01:20:23.340 So if you can't see what's underneath it. But the other thing is that when you run on a soft surface,

01:20:29.060 you stiffen your leg. This is amazing thing about our leg spring. You have this ability,

01:20:34.500 this innate ability to modulate the stiffness of your leg. So when you land on hard surfaces,

01:20:40.880 you make your leg compliant. So if you're going to step off of a three foot step and land on concrete,

01:20:47.460 you're going to land as soft as you can. You're going to flex your ankles, your knees, your hips.

01:20:52.500 But if you land in sand, you're going to stiffen. You don't want to collapse into it. So you stiffen

01:20:57.740 on soft surfaces. And there's lots and lots of studies that have shown this. This is definitely

01:21:02.660 true. This is why when you have a cushioned shoe, we'll go back to that, that you tend to land hard.

01:21:09.240 If you train on grass, there's nothing wrong with starting on grass. It's fine. But when you train on

01:21:15.600 hard surfaces, it teaches you to be really compliant. And that's what Chris told me to do.

01:21:20.340 He said, start on the hard surfaces. If you're going to run, do most of your running on hard

01:21:25.160 surfaces, like people who compete, mostly always on hard surfaces, unless you're doing track,

01:21:30.380 then you need to train your leg to be compliant. I tell people, you can mix it up. It's fine. But

01:21:36.440 make sure you do a good part of your training on the surface you're going to do most of your running on.

01:21:41.100 So don't do all of it on soft surfaces, really. And again, if the hardest part is making your leg

01:21:47.520 nice and compliant. And when you make it compliant, you're actually using muscles to attenuate. So it's

01:21:53.660 work. It's work to make it compliant. So yeah, I would start that way.

01:21:59.420 Thanks for clarifying that. That's interesting. Now I want to go up the chain a little bit. You alluded

01:22:03.760 to the knee and I want to talk about other issues of the knee. So is knee valgus an issue? Are you

01:22:10.360 concerned with that? Do you see when a person's running and they have a significant valgus? And

01:22:14.840 I'll let you explain to people what that is. How much of an issue is that? And is that basically

01:22:20.080 always a pathologic finding, sometimes a pathologic finding? And does it always result from the foot?

01:22:26.700 There's a lot of questions there. I'm known for that, Irene. That's what I do. I'm going to give

01:22:31.060 you a lot of questions. I'm known for saying there's never a hundred percent of anything. I'll never say

01:22:36.180 always a never say never. There are people who have terrible alignment that aren't injured. And

01:22:42.380 there are people who have good alignment that are injured. And part of it is because these injuries

01:22:46.640 are multifactorial. And if we just take the mechanical part of it, part of it's related to

01:22:50.980 your structure. That's just how you're built and then how you move, your motor control, and then your

01:22:57.320 dosage, how quickly you ramp up and how much dosage you have. So you could have someone who has a problem

01:23:03.420 with their alignment, but they're keeping their dosage down so they don't get injured. So you can look

01:23:08.000 at them and it looks like that they should be injured, but they're not. That might just be because

01:23:11.860 they're keeping their dosage down. You could have someone that looks really well aligned and really

01:23:16.560 good mechanics, but because they did too much too quick. So it really is not a one-to-one. And here's the

01:23:22.580 other thing that's really interesting. You can have someone who's got knee valgus and have five people.

01:23:28.680 One could have a knee problem. It manifests as a knee problem. One, it could manifest as a hip problem.

01:23:35.360 Another person, it could be their medial foot. Another person could be their plantar fascia.

01:23:39.960 So it's not a mapping of one-to-one. And you can have somebody with knee problems.

01:23:45.320 One of them might have excessive valgus. Another might have a really stiff landing.

01:23:50.800 You see what I'm saying? So it's what makes it so much fun to figure out,

01:23:55.840 but it's not straightforward. It's not a one-to-one mapping. Having said that,

01:24:01.540 there are these patterns that we tend to see with injuries. So I had to kind of preface it with that,

01:24:08.580 but the two features that we see most often with injuries, and we've had over 700 through the

01:24:15.420 running injury clinic so far at our center, are high impacts, landing hard, and malalignment in general.

01:24:23.400 But the most common malalignment is a medialization of their leg. So when I say that,

01:24:29.600 I mean there's valgus. So the knees come in towards each other. So instead of the legs being

01:24:36.140 straight, the knees bow in. They can bow out. That's why there's other alignments. This is most

01:24:41.060 common though. The kneecap rotates inward. So the kneecaps start to look at each other,

01:24:46.340 a rotation inward of the leg often. And the pelvis drops to each side. Every time you land,

01:24:53.880 other side drops down, then you land on the other leg. The other side drops down. It can be just on

01:24:57.780 one side. All those seem to go together and they're the most common. And I think that a lot of that

01:25:04.980 relates if we talk about evolution. It goes back to the fact that when we sit, as much as we're sitting

01:25:11.860 now in our lives, we don't have the core stability. Short of if we're really going at it and really

01:25:17.940 making sure that we're addressing our core, which not a lot of people do. And that core instability,

01:25:22.580 just like the instability of the foot. You don't have the core muscle. We call it the

01:25:27.060 foot core for a reason. It's just like the lumbopelvic core. If those muscles aren't doing

01:25:31.620 their job, then the prime movers can't do their job and you have malfunction. So I believe that we

01:25:37.920 see a lot of this instability because we are so weak in our cores and we don't have that kind of

01:25:43.280 stability. And those kids I mentioned from La Sierra High School, I bet you if I looked at them run,

01:25:47.940 they wouldn't have those kinds of mechanics. So it is a very common kind of problem that we see

01:25:53.220 in terms of mechanics is that valgus. Irene, when you talk about the elevation and depression of

01:25:59.380 the hemipelvis, I think everybody knows what you're talking about, which is basically the hip hiking

01:26:03.380 that occurs one side to the other. It's actually not a hiking. It's the other hip dropping. I see.

01:26:08.720 So the one side is actually staying level. The other side's actually depressing. Okay.

01:26:12.780 Right. And it's the side. So if you're on your right leg, it's the right hip that keeps the left

01:26:19.260 hip from falling down. So it's the opposite side that drops. So if I'm my right leg, it's my right

01:26:27.080 hip muscles that hold my hip, my pelvis level. I got it. Because the left foot's not on the ground.

01:26:33.440 It's not under load. It's swinging through. So this drops unless these muscles are doing their job.

01:26:38.780 And then when you go to the other leg, so now I'm on my left leg, then my pelvis is going to drop to

01:26:44.160 my right because the left hip muscles are not doing their job. You mentioned the core, which is

01:26:50.500 obviously a very broad term. So are you referring to the intrinsic muscles of the pelvis along with the

01:26:58.460 transversalis fascia and all these muscles? Or is it also in part the result of the adductors and

01:27:06.920 abductors being too weak? This is such a complicated part of the anatomy that it's hard to get a handle

01:27:13.740 on what muscles. Let's use the example you gave. So the right foot is on the ground striking. The left

01:27:20.780 foot is now sweeping. The left hip has now gone down, right? So what's not firing that should be?

01:27:28.880 I think it's all of the above. I think you need that stability of the small muscles that actually

01:27:35.080 stabilize the hip and its socket. I think you need the abdominals that prevent the pelvis from

01:27:41.900 anteriorly tilting. So you get a tilting of the top part of the pelvis forward and the back part of

01:27:47.160 the pelvis backwards. That tilting is also associated with rotation inward of the thigh. They kind of go

01:27:55.520 together. And then if the abductors are not doing their job, you get the drop. It really is all of it,

01:28:00.800 but you need that stability also of the core. And the core really is the sort of the transverse of

01:28:07.120 deep muscles that stabilize. And it's not always weakness. We think about it. We talk to our patients

01:28:13.660 and say, you've got your hardware and your software. Your hardware is the strength of your musculoskeletal

01:28:20.480 system. That's your hardware. But the software is your motor pattern. So we see people who are not

01:28:26.780 that weak, but they are a mess mechanically because they just aren't using the muscles in the way that

01:28:32.800 they should. Another injury I'd like to ask you about is, which I've struggled with not in a long time. I got

01:28:39.280 it under control by strengthening my abductors, but is IT band. And a lot of people get this really

01:28:47.300 miserable pain on the side of their knee. I think most people are familiar with what that is,

01:28:52.160 but the IT band is this sort of tendinous thing that connects to a muscle called the tensor fascia

01:28:58.120 latae, which is basically at your hip. What are some of the things that you see exacerbating that IT

01:29:04.580 band syndrome? And do any of them actually tie all the way down to the foot and what we've talked about?

01:29:10.320 It can. That's a very good point. So we did a study looking at people with IT band syndrome

01:29:16.520 compared to healthy controls, and we looked at their mechanics. And we have two studies. One of them

01:29:22.200 was retrospective. That means that these people were now healed, but they had a history of IT band

01:29:28.720 syndrome, and we compared them to their controls. Then we had another study where we had people who

01:29:34.620 were healthy to start out with, and we looked to see who got injured and who did not. That is a stronger

01:29:40.780 design because there you can say they didn't have the injury. Here are the mechanics, and it led to

01:29:46.500 this injury. Whereas when you look retrospectively, which is easier to do from a scientific standpoint,

01:29:52.480 you've got to wait for the injuries in a prospective design. But in a retrospective,

01:29:56.820 you can just go and get people who have a history. But you don't know whether the injury caused it

01:30:01.700 or it was there before. We've done both kinds of studies, and we found the exact same results,

01:30:08.220 which to me is very compelling. What we found in the mechanics was that people with IT band syndrome

01:30:14.280 had greater inward angulation of their thigh, which can kind of contribute to valgus. And the reason that

01:30:22.920 that's important is because the IT band attaches to the distal thigh. There's a very robust attachment,

01:30:30.000 not just to the tibia, Gertie's tubercle, which is a little bump on the lateral lower leg bone,

01:30:36.840 but it also attaches to the end of the thigh bone. And so when the thigh comes in too much,

01:30:43.140 it stretches it. The other thing that stretches is when the pelvis drops, because the IT band comes

01:30:49.380 all the way up, and it does insert a tensiofasciolata and the glutes. So the drop of the pelvis

01:30:56.120 and the inward angulation of the thigh just puts a big strain on the IT band. And if it's already

01:31:02.660 tight, as you flex and extend your knee, it goes back and forth over the bump on the lateral end

01:31:08.860 of the thigh bone. So it just rubs and get this pressure. You can have that pressure, excessive

01:31:14.220 pressure to start with. And then if you increase the amount that your hip comes in and your pelvis

01:31:19.840 drops, it just further exacerbates it. So that's one cause of it. The other mechanic that we saw,

01:31:27.100 both retrospectively and prospectively, again, very strong results, was internal rotation of the tibia.

01:31:33.860 So the tibia is a lower leg bone. Now the IT band also attaches to the tibia. So as the tibia rotates

01:31:41.860 inward, it stretches the IT band. So when you ask me about the foot, the tibia is connected to the

01:31:49.820 leg bone is connected to the foot bone. So if you're excessively pronating, it can excessively

01:31:55.500 internally rotate your tibia. It can be from the foot and it can be from the hip. And when you think

01:32:01.480 about the knee and all kinds of knee injuries, it's the joint in the middle of the foot and the hip.

01:32:06.980 So it often is the victim of issues with the foot or the hip.

01:32:11.580 Pronating in this context is the opposite of inversion?

01:32:15.860 Yes. Pronating and supinating, it's just another term for it. But yeah, so you're rolling your foot

01:32:21.440 inward too much. The analogy would be the eversion, inversion and eversion. Sometimes also referred to

01:32:27.800 as supination and pronation. That's very interesting. It speaks to this idea that you've got to be able to

01:32:33.960 at least try to identify the cause of this with some gait analysis. I think in my case, when my IT band

01:32:39.960 hurt, I just assumed it was the first explanation you gave. And it was because once I took on a robust

01:32:48.640 program of strengthening the glute med, basically, especially from an eccentric standpoint, so really

01:32:55.960 did a lot of eccentric strengthening of the glute med, all of a sudden you now have the ability to keep

01:33:01.760 the femur out. You take that valgus and lengthening away of the IT band and the pain gets better. I was

01:33:08.300 experiencing it on a bicycle, actually, not running. Nevertheless, but the point here is I never even

01:33:14.280 thought about it through the lens of if you have enough eversion or pronation, you're going to pull

01:33:19.880 on the other head of that tendon, which is attaching to the tuberosity of the tibia. I mean, it's really an

01:33:25.440 amazing field you're in because it is truly an engineering field. I mean, it's a structural.

01:33:31.380 One of the things I'm doing with my daughter right now this summer is we're working on physics.

01:33:36.080 She's in sixth grade. It's more about the fun of physics, but last week we worked on free body

01:33:41.460 diagrams, drawing forces and the direction of this force, the direction of that force and the magnitude

01:33:47.980 of this versus that. And we're basically just doing Newtonian physics and going through the three laws.

01:33:52.520 This would be a great thing for me to now show her as she's sort of thinking about this muscle's

01:33:57.840 pulling this way, but if this one's pulling that way, look what could happen.

01:34:01.720 And the ground reaction force is another great example because they are equal and opposite.

01:34:06.380 It's Newton's third law. You push down, the ground pushes you up. So when you push down on the ground,

01:34:11.600 you're a free body diagram of the world. You are pushing down on the world, but the world's so massive,

01:34:17.240 it doesn't move. And you get all the Chinese people on the other side, they're pushing up,

01:34:20.460 on the other side of the world. But the force that's coming back at you because your mass is

01:34:26.200 so much smaller creates your movement. So it is all physics. And this is why I have loved being

01:34:31.500 in this field is because I get to marry physics with medicine. Let's go back and close the loop

01:34:35.980 then on that sort of force discussion around how it is that joints can experience an amplification of

01:34:43.520 that force. So the reason that it amplifies the force is because the ground reaction force,

01:34:50.880 the muscles have to respond to the ground reaction force. And so if you have a force that is directed,

01:34:57.540 say, let's take the knee and it's directed behind the knee, it's going to create a flexion moment

01:35:02.820 on the knee. And so the knee has to extend in order for you to be able to prevent yourself from

01:35:10.980 collapsing. So it creates these muscle forces around the joint. And when the muscle forces

01:35:17.800 act around the joint, they compress the joint inward. And so they create an increase. That's

01:35:24.180 how they get amplified. It's really amazing because, and this will be probably more than you would want

01:35:29.500 to explain to a 12 year old, but this is where the free body diagrams become really complicated

01:35:34.960 because it's not just, I hit this thing with 200 newtons. It hit me back at 200 newtons. No,

01:35:43.900 that 200 newtons gets into the joint. And then the joint has its own internal moment arm. That's going to

01:35:50.560 add, as you said earlier, potentially seven X that force. And then of course, depending on the length of

01:35:57.600 that moment arm, I mean, we're talking about really serious forces here. Do you ever just sit back and

01:36:03.520 look at this and think, how the hell did we even evolve? Like it's so remarkable at what our bodies

01:36:09.000 are capable of, isn't it? Yeah, it is. And the fact that we're so adaptable is the thing that's

01:36:14.920 amazing. I mean, this is why I love mechanics because we can adapt. We can't change our structure

01:36:20.920 short of doing osteotomies, which I'm not qualified to do, meaning making changes in alignment in the

01:36:26.920 bones. Mechanics though, is something that's very modifiable. And for a long time, people did not

01:36:33.560 believe that. When I first started in this business, I was a young scientist and I went to a meeting and

01:36:39.520 I talked about gait retraining runners. Wow. I got virtual tomatoes thrown at me. I remember it.

01:36:46.740 And people saying, you can't change the way somebody moves, that we have these automatic generators of

01:36:53.160 gait. But if you actually study it, we do have the ability, super cortical ability to modulate

01:37:01.740 our gait pattern. And so it's been really fun to be able to say, okay, I see that in your gait.

01:37:08.580 I'm going to change it. It's not easy. I have to say it's not easy because in order to change somebody's

01:37:14.880 gait, you have to give them a lot of practice. They've got a certain pattern that they have,

01:37:20.900 and they've had it for 20 years, 40 years, 60 years, depending on who, how old they are.

01:37:26.880 And we've done gait retraining across that age span. You need to be able to give them feedback

01:37:31.960 to begin with so that they start to learn, okay, this is right. This is what I see that's right.

01:37:37.400 If it's visual feedback, this is what it feels like. Now I know what's right. Then you have to

01:37:43.700 start to fade the feedback. So now they have to feel what's right without having it because they're not

01:37:48.160 going to have it. And then you have to give them a lot of practice. That process of changing your

01:37:53.520 gait, though I think it's worth it if you've been injured and we think that the mechanics are causing

01:37:58.480 the injury, you have to be patient with it. And even when you finish. So in our program, I started

01:38:04.380 to tell you, we have a, say on average, a two month pre-gait. Then they have a three time a week,

01:38:11.140 four week gait retraining on the treadmill. And then they go out for 10 weeks under our supervision,

01:38:18.000 they're out running on their own, but we check in with them. They come and see us at two weeks

01:38:22.300 and at four weeks. And they have to start really slow. They can't go really fast because even though

01:38:29.700 they've maybe got the pattern now, if they want to start ramping up, they got to give the tissues

01:38:33.880 the time to adapt. It is a process that takes patience. And if someone's going to come to us and

01:38:40.700 say, Hey, I'm doing this New York marathon two months. We say, we can't do this right now.

01:38:45.400 We'll give you some exercises and try to help you out, but you're going to need a lot more time

01:38:50.240 than that. What percentage of those patients, Irene, are people that have no injury, but have

01:38:56.020 bought into this thesis, which is my gait's probably not adequate and I'm going to get injured one day.

01:39:01.500 So I want to do this in a totally preventative manner versus people who are actually under the

01:39:07.060 spell of some injury at the time that they show up.

01:39:09.140 So in order to be able to have the treatments paid for, you have to have an injury. They wouldn't

01:39:15.680 get it covered in terms of retraining. So I would say we have had people come in for just an eval

01:39:21.960 for us to kind of take a look at their gait. Sometimes a spouse will give it to their spouse

01:39:26.140 as a Christmas gift or something like that. But in terms of people who come through the program,

01:39:31.320 it's a hundred percent people who've been injured.

01:39:33.660 Which seems to be a bit of a failure of the system. That's sort of the same problem we have in

01:39:37.120 medicine, which is, look, we'll wait till you have type 2 diabetes, at which point it's going to cost

01:39:42.140 the healthcare system somewhere between $7,000 and $12,000 a year, including insulin. But God forbid,

01:39:48.600 we spend, I don't know, $500 a year on prevention to make sure you never get type 2 diabetes. It seems

01:39:55.340 to me that a great investment, at least for the people who are motivated, would be taking people who

01:40:02.100 are not injured and teaching them what you were talking about.

01:40:05.300 So let me tell you about a study of one of my colleagues. He was one of my postdocs that he

01:40:09.880 went on and did a study where he took 320 novice, meaning they'd been running a year or less.

01:40:17.060 I think they'd all been running at least a year, but not much more than that.

01:40:20.280 And then what he did is he took half of them and had them train on a treadmill because the same kind

01:40:26.540 of retraining program we have, where they had a monitor and they could see those impacts that I was

01:40:31.640 telling you about. And I can give you some graphs of these. And so what they did is they were told

01:40:36.440 to get rid of the impact, to land softer. And he didn't monitor what they did, but in order to do

01:40:42.340 that, they probably got off their heels. And then the other group went through the same eight sessions.

01:40:47.600 They did eight sessions. They slowly ramp up from 10 minutes to 30 minutes over those eight sessions.

01:40:51.900 And then he followed them for a year. And these are healthy people. 62% reduction in injuries in the

01:40:59.680 group that was trained to land softer. 62% reduction over the course of a year. That's huge.

01:41:07.040 What's most amazing to me in that study, if I understand you correctly, Irene, is that

01:41:10.680 they weren't given an explicit instruction of how to change their form. It was basically,

01:41:16.220 they adapted to the visual stimulus of just make that spike smaller. And they figured out what to

01:41:25.040 do. And then in what sounds like a relatively short period of time, made the adjustment,

01:41:29.300 the adjustment stuck. Am I replaying that correctly to you? Yes, I think you are. The thing that we're

01:41:35.100 not sure of because he didn't, and this is one of the criticisms of the studies that he never brought

01:41:39.100 them back later to see if it did stick. So not sure. And it may be that some people did get reduced

01:41:47.600 the spike where others may have eliminated it by being on the ball of their foot. I would like to

01:41:51.940 know if the people on the ball of their foot had less injuries. Dan's group did a study, Dan Lieberman's

01:41:57.100 group did a study looking at its retrospective of the Harvard track team and found that the kids who

01:42:04.340 were forefoot strikers on the track team had half of the running, he classified them into overuse

01:42:11.500 injuries. And they had half of the injuries of the rear foot strikers. Because it's retrospective,

01:42:17.640 it's not as strong as being prospective. But another really interesting piece of information

01:42:22.740 in terms of how this might apply to running teams is that there's a group, it's a close Christian

01:42:29.540 community, and I won't name them because they don't want to be named, but it's a close Christian

01:42:33.860 community. The doc of the close Christian community basically went through medical school,

01:42:39.160 he's a physician, and he had all kinds of foot related problems. And all of his residents and

01:42:44.400 fellows and colleagues who were giving him advice, he got like three pairs of orthotics and nothing

01:42:48.400 helped him. It was when Born to Run had come out and he kind of looked at it and put the book down

01:42:53.280 and they decided to read it. And then he decided that he's going to try to go barefoot and minimal.

01:42:58.640 And it cured his problem, resolved his problem. I can say it's cured it, but it resolved his problem.

01:43:03.160 So now he, as a member of this community, they pay for your medical school and then you come back

01:43:09.020 into the community. And he's the physician in the community. The track team of this community

01:43:16.160 had had some members that had season ending injuries, running injuries. But before that,

01:43:22.040 he started to prescribe minimal shoes for some of his patients that weren't responding to standard of

01:43:28.120 care. So he used to really send all of his foot related patients to a podiatrist. And then he

01:43:35.180 started deciding, I'm going to try this because it worked for me. So this first woman who just wasn't

01:43:41.120 getting better with the orthotics and the standard of care. So he said, look, I know you may think I'm

01:43:44.880 crazy, but would you be willing to try this? And it worked. And they tried it again. And he tried it

01:43:50.100 again. And he tried it again to the point where he was so convinced that this was working. They

01:43:55.600 actually decide the footwear. They have a clothing store because nobody pays for anything. It's all

01:44:00.900 common money. And they had a clothing store. He ordered minimal shoes. So 80% of their community

01:44:06.880 now are in minimal shoes. And he showed a graph of the number of referrals to podiatrists went down

01:44:15.140 as his prescription of minimal footwear went up. And with that success in a normal community with

01:44:20.760 walking, he decided to try it with the cross-country team. He was the physician for the cross-country

01:44:26.320 team. And the coaches went along with it. So they basically started in January and had the kids start

01:44:31.780 transitioning in January before the September season. So they had, what, nine months of slowly

01:44:37.220 working into the minimal shoes. And they ended up that year having no injuries and winning their

01:44:44.900 division. And then they had a second year of, I think, winning. They got bumped up, even though

01:44:51.360 we're a small school because they were so successful, they got bumped up to the next division. And I think

01:44:55.620 they came in second. And they had basically no injuries, like one sprained ankle, but no tubular

01:45:00.760 stress fractures, no plantar fasciitis, no anterior knee pain, no ITB, all the things that you see.

01:45:06.360 And he's had a third year. I think this is the third year. And then we had COVID. Yeah, he had a third

01:45:10.880 year because COVID. I haven't really talked to him since. I can't publish this because they want to stay

01:45:15.480 private. And I understand that. But it's just unfortunate I can't publish it. But basically, it's just an

01:45:21.780 example. When you have this kind of ability to control it and you look and see that it can have that

01:45:28.180 kind of result. This is why I say, I would love to see people all start their kids this way and have

01:45:33.980 people run this way. I think our running mechanics would improve. I think we wouldn't have the same kind of

01:45:38.560 problems with feet. I don't think we'd have the same kind of problems with these. This is my hypothesis.

01:45:42.720 And I admit it's a hypothesis. And some people think I'm a little bit crazy. But I don't. We're really

01:45:48.420 coming back to your points about evolution. It's the way that we evolved to be. And so I feel like we

01:45:54.860 have everything we need. And that when we start to add shoes, we haven't talked about this much,

01:45:59.480 you add torques to the ankle, knee, and the hip. So when you look at the torques at the ankle,

01:46:06.940 knee, and hip, they are the lowest with barefoot. That's like your gold standard. And the minute you

01:46:12.340 start to add footwear, low heel and higher heel and more athletic shoes with more flares to the

01:46:19.260 outer sole, the torques go up. Now, does the increase in torques cause a problem? I don't know.

01:46:26.120 But they certainly are increased above what we're adapted for. It's like, how do we facilitate

01:46:32.360 natural movement in a modern world? And it's a challenge.

01:46:36.240 I share your view. I share your bias. I'll say that, that if you took every kid when they were

01:46:41.660 born and you kept them in minimalist footwear and they never sat down in chairs. So you squatted,

01:46:48.240 you sat on logs, you stood, but this idea of a desk and a chair was taken away. I would put those as

01:46:55.820 two of the five most important things you could do. Like if I could be czar of the world and I could have

01:47:01.120 five things that I would do to change human health. And I was given the liberty of going

01:47:07.080 and starting at the beginning. So saying you could implement these changes from the moment a person

01:47:11.560 is born. Those are two of the five I'd take right there. I couldn't agree with you more because we

01:47:16.960 see so many problems with feet and hips and it's all related to that. I just couldn't agree with you

01:47:21.860 more. I think that we got us started there. And I think that we would be solving a lot of the

01:47:27.320 problems. We're going to get phys ed and this is going a little off topic, but I'm really wanting

01:47:33.380 to see phys ed back in schools every single day and not just dodgeball, but activities that are

01:47:40.160 actually calisthenics, pushups, sit-ups, using your upper extremities, monkey bars, kids hanging

01:47:45.940 in front. I mean, we don't do that anymore. I think we need to really encourage that kind of activity.

01:47:51.100 The statistics are overwhelming. It's just so unbelievable. I think by the time adolescents,

01:47:57.900 you're 12 to 17 years old, on average, kids have at least one chronic disease.

01:48:04.680 Not all kids. Maybe it was 40% of kids. I can't remember the exact numbers, but it was really

01:48:09.080 alarming. And a fairly large percent of them had two chronic diseases as adolescents. That to me is

01:48:16.080 really alarming. We shouldn't be having chronic diseases as kids. Diabetes is really high.

01:48:21.500 In kids now, it's grown. It's really increased. Yeah. And I think the chronic injury issue is

01:48:27.040 another problem, which is if you're a kid that if you're having knee pain and hip pain and all these

01:48:33.020 sorts of issues when you're 18 or when you're in college, it's not like it's going to get better

01:48:38.080 when you're out of college without a very deliberate effort. We definitely need to get our kids so that

01:48:43.260 they're not doing a single sport. It's been shown that those kids actually burn out quicker. They get

01:48:49.100 injured at a higher rate. That it's important for kids to be using their bodies in a number of

01:48:53.840 different ways. That multi-sport athlete is much healthier than the single sport that's doing

01:48:59.320 soccer all year long. Yeah.

01:49:01.560 Irene, I got to say, I'm pretty glad that Hoover sent you that rejection letter 50 years ago,

01:49:10.440 right? Because I think the human condition is a better place for you not having become an FBI

01:49:15.280 agent, though I'm sure you would have been an excellent one at that. And despite what you said

01:49:19.460 about your patience, I don't detect in you someone who has an unhealthy amount of impatience. I detect in

01:49:26.340 you just the right amount of impatience, which is you've kicked the hornet's nest enough. You've

01:49:31.160 stirred up the pot enough. But what impresses me the most in this discussion, and I knew from

01:49:36.300 reading what you'd written and sort of your credentials that this would be an interesting

01:49:39.780 discussion, but what doesn't come across in all of those is how malleable you've been in your

01:49:43.800 thinking and how many ways and times you've changed your view based on new evidence that's put

01:49:50.320 forth. And that leads me to believe that five years from now, if we speak again, you're going to have

01:49:54.260 something different to say, which I always view as a sign of good thoughtfulness. With that said,

01:49:59.680 I want to thank you very much for your time. I know people are going to enjoy this hopefully half

01:50:03.100 as much as I did. Peter, it's been really fun talking to you because I think we are like-minded

01:50:08.200 and like-spirited. Thank you very much for the opportunity. I really have enjoyed it.

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The Peter Attia Drive - September 14, 2020

#128 – Irene Davis, Ph.D.： The evolution of the foot, running injuries, and minimalist shoes

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