AOFAS Thought Leader Series-From Orthotics to Minimal Footwear: An Evolution of Thought

From Orthotics to Minimal Footwear: An Evolution of Thought

Video Transcription

It gives me great pleasure to introduce Irene Davis. Dr. Davis is professor of physical medicine and rehab at Harvard Medical School,  and she is the director of the Spaulding National Running Center. Dr. Davis is a superstar in the world of human movement biomechanics.  She is a past president of the American Society of Biomechanics and is one of a very select group of biomechanists to be honored as a fellow of that society.  Her research focuses on the relationship between lower extremity structure, mechanics, and injury,  and extends the development of interventions to alter mechanics through gait retraining. Her interests also include the effects of minimal footwear on mechanics and injury.  She is going to speak today about the evolution of our thought in shoewear. Please give a warm welcome to our 2017 research guest speaker, Dr. Irene Davis.  Good morning, and thank you. It's an honor to be here, and I want to thank the organizers for asking me to come and speak to you. This is a great group.  I'm going to give this talk in the content of an evolution of my thought, because I think it's important that we do evolve in our thinking.  For those of you who knew me early in my career, you're going to know that this is a big evolution in my thought. It starts with my research beginning as a Ph.D. student.  I was at Penn State with Dr. Peter Kavanaugh, who is one of the pioneers in the area of running mechanics,  and I was really interested in understanding the relationship between the foot and the knee,  and actually conducted my Ph.D. looking at the effect of foot orthotics on patellofemoral motion in people who are excessive pronators.  Now, this involved a pretty intense type of data collection. We had to put intracortical pins into the patellofemoral joint,  because you can't put external markers on it and get very valid data. So you can see this was a difficult, challenging problem,  and it's the same kind of problem that we have in the foot, and I'll talk more about that in the afternoon session in the research session.  But this dissertation is often your springboard for research.  So when I moved on to the University of Delaware, my very first study was looking at the effect of pronation on the knee,  not the patellofemoral joint, because I really didn't want to put any more pins in people, but I did want to understand how it affected the knee.  So I took a group of runners, 20 who had normal rear foot motion, and 20, as you can see, had excessive rear foot motion, peak of 20 degrees.  And what we did is we looked at their knee motion. We found that they had increased knee flexion, which is going to increase the load of the patellofemoral joint.  They also had increased internal rotation and increased valgus. So this is sort of what we were looking at with that increased valgus.  And increased flexion and increased valgus, for sure, are mechanics that have been associated with pronation and with the development of anterior knee pain.  So where do we go from there? So if we think that pronation is influencing the knee and the patellofemoral joint, then how do we affect that?  And my first thought, my first go-to was orthotics. And so I started with a series of studies looking at foot orthotics.  In this particular one, we were looking at foot and knee coupling. We also conducted a study looking at the inverted orthotic. I'm not even sure if this is even still being used,  but it was a very rigid graphite inverted orthotic and compared that to a standard device and looking at both foot and knee mechanics.  Also did some work looking at the custom and semi-custom devices and their influence on motion control as well as comfort.  So really did a number of studies in this area of foot orthotics. My underlying belief number one is that many feet are not strong enough to tolerate the loads of standing,  sometimes walking, and running. And this is the reason for the prolific use of foot orthotics in individuals who have musculoskeletal problems.  At the same time, I was also conducting studies on the effect of foot strike in runners.  And I know that there have been studies that document that 75% to up to 95% of runners in standard shoes land on their heels, and only 1% actually land on the ball of their foot.  We also know, and there's lots of studies that have shown this, that they result in very different ground reaction forces.  On the left, you can see there's an impact force that is associated with that heel contact. And on the right, it's a very gentle rise to peak and that impact force is missing.  We also know that when we look at the kinematics, this just happens to be the foot and the sagittal transverse and frontal plane.  I just want you to notice that all of the differences in these foot strike mechanics happen very early in stance. The same with that impact peak that happens very early.  And these kinematic factors, the movement patterns, are different only early in stance. But if you look later, they're very similar across the board.  So my second underlying belief at this time was that rear foot striking is actually the norm. I mean, up to 95% of runners run that way. It must be our norm.  But that impact transient is actually a normal characteristic of the vertical ground reaction force.  But at the same time, there were animal studies that suggested this impact force might be related to injury.  So a study by Radin basically looked at rabbit tibia and applied impulsive loading, so like an impact load, and found that those rabbit tibia developed tibial stress fractures.  In another study of bovine joints, they actually first applied a very rhythmic type of load, and they had no damage at all.  But once they started to introduce an impulsive load, then the cartilage started to degrade. So both bone and cartilage are susceptible to these high rates of loading.  So we wanted to conduct a study in humans, and this was a collaborative study with my colleague Joe Hamel at the University of Massachusetts.  We studied tibial stress fractures and looked at people who had a history of tibial stress fractures and studied their mechanics.  So what we studied were tibial shock, that's the shock wave that travels from your foot to your head, as well as ground reaction forces.  Now, tibial shock is important because your body is a big filter. By the time it gets to your head, you want it to be about 1 to 2 Gs  or you're going to have a shaken adult syndrome, which we don't want. So your body has to filter it. So the higher that shock is at the foot, the greater the filtering,  because it's going to be 1 to 2 Gs no matter what at your head. So the lower the shock in the beginning, the less your body has to attenuate that shock.  What we found is that these individuals who had these bony injuries did have higher tibial shock and higher vertical impact forces,  and also looking at the slope of that first rise to peak, we found that they also had higher rates of loading.  So the next phase in my research was to then take off my scientific hat and put my clinical hat back on and say, okay, what do we do about this, Irene?  As a physical therapist, what do I do? So we actually started to develop these ideas of retraining gait patterns.  So we put a very small accelerometer, as you can see, in the distal medial tibia. It was about 3 grams. We tightly affixed it to the tibia, had the person run,  and this is their tibial shock with each foot strike. So there are four foot strikes there. It looks like an EKG.  And what we did is we gave them a line that we considered to be a normal amount of shock. It was usually about 50% of what they were running at.  And we asked them to just soften their foot strike. And in a single session, they can do this. They can't maintain it because you just don't have the motor pattern  or even the muscle control to do that, but they can do it. And if you can do it once, then you can actually reinforce that and change that movement pattern.  We also utilized a faded feedback design where we actually increased the run time over eight sessions and gave them 100% feedback during the first four sessions.  And you can see in the last four, we start to fade the feedback because motor control principles say that you've got to fade that feedback  so they learn to depend on their own internal cues. So we just basically turned off the screen. Here are results.  So in terms of tibial shock, which was the variable we gave them for feedback, it was reduced by about 30%.  And although we weren't giving them feedback on the impacts and load rates, the slope of that first rise to peak and the value of that first peak,  they did reduce it by 16% on the impact peaks and 22% on the load rates. And those reductions actually maintained out to a year.  So while I'm conducting these impact studies and these orthotic studies, I get a call from Chris McDougall. And he was a journalist for The New York Times,  and he was doing a story on the new shoe that just came out, the Nike Free. And he said to me, Hey, what do you think about those Nike Frees?  And actually he left me a message, and I just emailed him and said, Hey, I'll get back to you, because I had nothing to think about them.  I hadn't even thought about them, and you don't want to tell a journalist that. So I actually did a little bit of research on this Nike Free.  I'd heard about it coming out, but I hadn't paid much attention, because at this point I wasn't paying a whole lot of attention to footwear.  What I found is there was a study that had just been presented at the International Society of Biomechanics in Cleveland, and they found that the muscles of the foot,  the intrinsic muscles of the foot actually increased in size by utilizing this Nike Free shoe over a period of five months. And basically the shoe has no arch support,  so basically removed the support of that foot. So I started to question my underlying belief, number one, that feet need to be supported and need chronic support.  And in fact, I believe now that we actually decondition them when you put chronic support, when they have chronic support.  If you look at someone who has neck pain, you would never do this. I would never do this as a physical therapist.  I wouldn't put a permanent shoulder brace on someone who had a shoulder injury. Would I brace them initially? Sure.  Would I then try to wean them off of the bracing and strengthen them and utilize motor control principles? Absolutely. But we don't do that with the foot, and I didn't either.  I mean, this was my philosophy too. I felt like they're going to need it forever, and they're going to need it in every pair of shoes,  they're going to need it in their walking shoes, their running shoes, etc. So I started to really kind of question this and question the idea of chronic orthotic use.  I'm not talking about any orthotic use. I'm talking about chronic use. Well, the next year, Chris called me again and said, Hey, I want to come to your lab.  I would like to look at running myself in a pair of these shoes, these new shoes, compared to a pair of these Nike Air Pegasus, and also to barefoot. So basically, he ran barefoot,  and we compared his rates of loading across those three conditions, and what we found is that the impacts were actually the least when he was barefoot.  It was really interesting, because this got me thinking again, right? And I didn't know it at the time,  but he was actually starting to develop his background information for this book, Born to Run. How many people have read Born to Run? Quite a few. Okay.  So now a storm is brewing in my mind, right? So I know, and we started looking at other injuries besides bony injuries  and finding that these load rates were actually related to anterior knee pain, to plantar fasciitis, and maybe to others that we hadn't looked at.  We looked at some of the big injuries just because they were the most prevalent. Those were retrospective studies. We conducted a prospective study and found that those individuals  who go on to develop an injury that needs medical care, so the ones that are more chronic, significantly greater impact peaks and load rates. This is prospective now.  Before they got injured, they had baseline higher load rates and impact peaks than those people who had never been injured before.  So again, now this is prospective data, more compelling. And when I looked at forefoot striking, they don't have an impact.  And if we look at barefoot running, it's a forefoot strike pattern, and barefoot is how we started. So this is why this storm started brewing in my head  when I started thinking about all of these things and thinking. I started questioning my own clinical approach. And I started asking myself this question.  Could footwear and impacts actually be contributing to injury? Because up until now, we had thought that that impact peak is a normal part of ground reaction force,  barefoot striking is normal, et cetera. When you think about it, up to 79% of runners get injured in a given year. 46% of them will be recurrences.  It's really interesting because that's something that we actually evolved to do. We had to run for our survival. And it doesn't make sense.  It would be like birds getting wing injuries or fish getting fin injuries at that same rate doing something that they're meant to do.  So it really started to beg the question for me, are we doing something wrong? And again, this is shaking my own beliefs.  And I became aware of this mismatch theory of evolution that basically says we are not living the lives that our bodies were designed for.  So what you're doing right now is one of the most unnatural things that we do in our lives. We were designed to squat. It's why our patella cartilage is the thickest in the body.  And so sitting has really caused a lot of problems. I think it's a big part of why we have so much core instability.  But the food we eat, the air we breathe, and certainly our activity level.  And this theory suggests that it's in part the cause of many of the noncommunicable diseases that we have today, the preventable diseases.  And I want to extend that to running and to the foot, because I believe that we are not using our feet and we're not running in the way that we are meant to,  and that that's leading to greater impacts that are going to be increasing our risk. It's also leading to deconditioning of the feet, which again is going to lead to increased risk.  So I think with a little tongue-in-cheek, maybe we have a disevolution of the runner. Because our foot, and I'm going to talk more about the amazing feet that we have,  and you guys will really appreciate that being the group that you are, this afternoon in the research section.  I'm going to talk a lot about the research that we're doing in foot strengthening and those kinds of things. But it is incredibly well suited for standing and walking and running.  There are many benefits of doing this barefoot. So barefoot individuals actually have higher arches. And this is a study that was done back in 92.  And so it's been around for a long time. It's 2,300 Indian children from India, not American Indian.  And about a third of them came from communities where they wore closed-toed shoes. A third came from communities where they wore open-toed sandals.  And a third came from communities that were barefoot. And these are the results. Flatfoot was most common in the communities where they wore closed-toed shoes,  which are assumingly probably have some type of arch support in them. And least common in the kids that went barefoot. This is so counterintuitive.  When I was a young PT and I had my children when they were young and toddlers, I was looking for those shoes that had the best arch support, stiff heel counter.  And now when my grandchildren come over to Mimi's house, we take the shoes off and we just go barefoot.  So I think that they suggest even back in 92 that this might actually be detrimental to the foot. I think we need to start thinking differently about this.  When you look at barefoot runners, at least 80% of them don't land on their heel, and we know that that results in lower impacts. They have shorter strides.  They have higher cadences, which is believed to help reduce the loads at the hip and the knee. In terms of the knee, this was a survey study conducted on about 800 runners  who had transitioned to truly barefoot running, no shoes. And they asked the question, what injury do you not have now that you had before? And the knee was the most common.  So this is actually forefoot striking or minimal shoes is really a very good intervention for knee injuries, and I'll show you why.  So if you look at the difference between a rearfoot strike and a forefoot strike, you can see that the rate of loading, that slope, is much greater  because you have the impact transient in a rearfoot strike. So at the same point in time, early in the gait cycle, your force is higher.  And let's just talk about the patella-femoral contact force. Your quad force will be higher. Your patella force will be higher.  You also have more knee flexion in landing and early stance when you are a forefoot striker. I didn't show you that data, but that is true.  So what happens is the patella gets more seated in the femoral groove. So now you have a larger surface area, lower force. That means you have lower contact stress,  which is actually one of the hallmarks of patella-femoral pain. The idea is that you just don't have good distribution of your force across the patella facets.  There are other benefits of being barefoot. This was a study looking at single leg standing in a pair of socks, toe socks, regular socks, and barefoot.  They used a measure called time to boundary condition, and what they did is basically looked at how long it takes before you lose your balance.  And believe it or not, a thin pair of socks reduces your static stability. So they lost their balance sooner when you had socks on than when you're barefoot.  So even a thin pair of socks results in a decrement in your static stability. We have a paper right now that's online, not published yet,  but basically looking at dynamic postural stability. So we did single leg landings because running is a series of single leg landings,  and we did it barefoot in a pair of minimal shoes and a pair of standard Nike Air Pegasus. Now you might think that the Air Pegasus with a wider base and more friction  would actually result in a more stable landing. Our measure was the dynamic postural stability index. It's a measure of instability, and you can see the results.  So as you add more between the foot and the ground, your landings are actually more unstable.  It's why ballerinas and gymnasts don't want to put a lot between their foot and the ground. Now there are pitfalls of barefoot running.  Basically when you are barefoot running, you tend to be on the ball of your foot. You do load the calf. You load the plantar fascia. You load the metatarsals.  So there are areas that get loaded more, and people who do it habitually actually have stronger calves, and there's data to support this.  We don't have data on the metatarsals. We'd like to look at that a little bit more closely, but clearly the muscles are stronger. The Achilles tendons are stronger and stiffer.  So it does require, if you haven't done this all your life, strengthening and adaptation, and I'll talk more about that later today.  And you can injure your foot because now it's exposed to the environment, whether it's cold or it's sharp objects.  I've never cut my foot running barefoot, but I have burned it on hot pavement and blistered it. So you have to be careful, and this is really why footwear was developed,  was to actually protect the bottom surface of your foot. If you look at the history of footwear, now remember we have been running for 2 million years,  and modern shoes with cushioning have only been around 50 years. So 50 versus 2 million is like a blip. It's like a nano, nano, nano, nanosecond, right?  But the first shoes that we actually found were these shoes that were found in the caves of Fort Rock, Oregon, and it was sagebrush bark held on with straps.  So basically just to protect the bottom surface of the foot. In terms of the history of running shoes, in the 1890s,  J.W. Foster actually developed a shoe that had a little bit of a spike. This was really the first formal running shoe.  In 1917, we had the advent of vulcanized rubber, so we made sneakers, and they're called sneakers because you can sneak up really quietly on people.  1925, Adi Dassler, who now is Adidas, actually perfected the shoe that J.W. Foster created. 1972 was actually the beginning of the cushioned heel.  1983 was the Nike Air Pegasus. It's the one shoe that is still around today. In 1992, we had the Brooks Beast, right? So we're just getting beefier and beefier.  In terms of minimal shoes, 2005 was really the beginning with the Nike Free coming out, and it really came out because the people at Nike were noticing that people at Stanford,  on the Stanford track, were actually training barefoot. And they thought, wow, let's try to make a shoe that actually mimics barefoot running.  And then 2009, when they were making this vibrant five-finger for boating, the barefoot community jumped on board because it provided a nice way to protect their feet  when they were running barefoot. 2010, we started to see some of the other new companies coming on board, Vivo Barefoot, Innovate.  2012 is when some of the big companies said, okay, we're going to get on board a little bit, so we're going to make our shoes a little more minimal.  But they weren't really truly all the way minimal, and I'll talk about that in a minute. And then now the pendulum swings all the way back.  These came out a little earlier in 2013, but really became popular in 2013. Now we have shoes that have 30- and 40-millimeter midsoles.  So no wonder why people are actually confused. And, you know, you have to ask the question, how does footwear matter? Because, again, I never used to think it did.  But this was a study, and it's a series of three studies done by Joe Knapik out of the military, and he combined them all into a meta-analysis.  So there's thousands of soldiers in the study. Half of them, he looked at their foot type, and if you had a low pronated foot,  you got a motion control shoe, neutral foot stability, high arched, rigid foot, you'd get a cushioning shoe. The other half all got a cushioning shoe regardless of their foot type.  So the idea of these differences in these shoe characteristics is it's supposed to reduce injury, but they found absolutely no difference between these groups in terms of injury.  And that's when I started questioning. These studies started coming out in 2010. That's when I started questioning whether this is really an appropriate way to prescribe footwear.  And, in fact, there's other studies now that show that pronators actually do better in a neutral shoe. So how did all these classifications come about?  I'm going to give you a little bit of history here. Jeff Johnson actually was one of the founders of Nike. He was there between 1965 and 1983. He was a runner in the 50s and 60s.  He said he was running in shoes that were called plimsolls. They basically had a rubber sole and a canvas top. He said they were well trained. They had legs of steel.  And he reports, and, of course, this is very anecdotal, that there were very few injuries. But what happened is in the 70s we had the running boon.  We did have more unfit people running, although back then it was still we didn't have the charity runners that we have today.  But we started to see, and we also had the beginning of the cushioned shoes. This was when we first started seeing the first injury reports associated with running.  There's nothing else in the literature until the 1970s. A newly minted runner's world actually published two studies, one in 71, one in 73,  and basically found that knee injuries were the most common and they were actually becoming more prevalent.  Peter Cavanaugh published a study as well and found in 1979 of the injured runners the knee injuries were the most prevalent. So now we're starting to see injuries.  It wasn't just knee injuries. I used that one just as an example. But what happened is Nike actually invited three well-known sports podiatrists, which you may know them.  So Steve Sabotnick, Harry Hlavnik, and Dennis Vixie. And these guys were the ones that were actually seeing some of these runners.  And they came in as consultants and they said, we think they have too much impact and too much motion. And it was really that.  They basically were worried about the injuries and asked these clinicians.  And I'm sure that this is what the clinicians thought, but there wasn't really any anecdotal evidence for this. And that's actually how those shoes were born.  So I'm in the middle of all this just really questioning about footwear and what should I be prescribing my runners. And at this time, I actually took a position.  I left the University of Delaware, took a position back home. I'm actually from Boston.  I wanted to get back home and what better place to treat runners and see runners but Boston with the storied Boston Marathon. So I headed up to Boston.  I developed and founded the Spalding National Running Center, which has a research component to it and a clinical component. And they are highly integrated.  So our clinic actually helps to generate research questions. The lab helps to answer some of those questions that we ask. And I started really looking now at footwear.  Because, again, I never really paid any attention to it.  So what we do now in every single patient, we've done over 600 of them so far, we videotape them with and without their shoes.  And I just want to give you one example because I've seen many of these kind of cases. This is someone who is running in a lightweight cushioned shoe.  It looks like they're pronating. They're having some knee problems. I had them run barefoot. And this is the same point in the gait cycle. This is mid-stance.  And you can see that they look like they've got a pretty neutral foot, right?  And when I put them in a pair of minimalist shoes, they have holes in them because we also use them for research, you can see that, again, you don't have the same degree of pronation.  So why is that? If you look, I really think in part it has to do with the lever arms that we have with shoes. So here's a bare foot. Here's the subtalar joint axis.  That's the vertical ground reaction force that hits you in the lateral portion of the foot. That's the moment arm. So that force times that moment arm is a pronatory torque.  Now, let's take that same foot, put it in a shoe, and the shoe doesn't have a really wide flare.  Same subtalar joint axis, exactly same force, but because you have some flare and the shoe is wider, guess what?  You just doubled the torque because you multiply the force times the distance. So now the pronatory torque has doubled.  When we look at the lateral ground reaction force, which occurs really early in the gait cycle, it also, it has a larger moment arm. It's smaller force, larger moment arm.  That contributes to the pronatory force. Now, if we were looking at a foot and where the foot hit the ground, that moment arm would be cut almost in half.  So you can see that that reduces it. And actually, there have been studies that show that pronation is actually greater in shoes due to the longer moment arms.  So, and other studies have been done. Casey Kerrigan, who was at PM&R at Harvard for a while, she actually looked at the torques at the foot, the knee, and the hip.  And she found that as you increase anything between the foot and the ground, those torques go up. So basically, our gold standard is barefoot.  And then we start adding abnormal torques. It's not surprising that we have these overuse injuries. I wanted to show you the effect of footwear when people forefoot strike.  We have some pilot data. We've not published this yet. But this is just an example of a patient who came in to us as well.  She had tried transitioning to a forefoot strike pattern in a pair of standard shoes. And what we find is that they tend to plantarflex more than they need to.  I don't know if you remember Chris's video. He was coming in, landing very almost horizontal. So you've got to get up over that heel. So they're plantarflexing more.  And they've got a flare even on the forefoot. So they've got to invert more.  And she ended up with Achilles tendonitis. Not surprising. I didn't give her any instruction. Just put her in a new pair of shoes that have no flare, no heel lift, or anything.  And you can see that her mechanics look different. So I then started looking at, well, how does footwear and foot strike interact? Like, do they matter? Do they both matter?  Is one more important than the other? So what we did is we took a group of people who were habitual. These are habitual rearfoot strikers in standard shoes.  We found habitual forefoot strikers in standard shoes, so cushioned shoes, and habitual forefoot strikers in minimal shoes. And what you hear ñ I'm going to orient you here.  Each of these bars you can think of as being related to the impact that the body experiences. It's basically the load rate.  And what I've done is I've not only shown you the vertical, but you also can see the anterior posterior medial lateral forces. And the resultant is the combination of all of them.  So what you see is if you look at the second set of bars, it's what we would expect. The highest impacts with a rearfoot strike.  Next with a forefoot strike, but in the standard shoes. But it's lower than rearfoot striking, which we've been talking about all along.  But that it's even lower when you're forefoot striking in a pair of minimal shoes. When you go to the resultant force, the first set of bars on the left,  what happens is because the anterior posterior medial lateral, and I think it's because of the plantarflexion, the inversion, they create higher impacts in those directions,  that the resultant force is identical to the resultant force of landing with a heel strike. So if you land on the ball of your foot as a forefoot striker in a pair of regular shoes,  or you land on the heel, actually your resultant impact is the same. So again, it says to me, strike pattern matters, but footwear matters as well.  So softest landings are really forefoot striking in a pair of minimal shoes, and this is what has fueled our approach.  What constitutes minimal footwear? I want to talk about this just a little bit. I believe it's shoes that have no motion control, no cushioning,  zero drop, no arch support, no midsole. But there is a new sort of group of shoes, which I'm going to call partial minimal shoes,  and a lot of people like to go there because it's kind of in the middle. You feel like, you know, I don't want to go all the way to a minimal shoe.  These are shoes like these that have minimal motion control, minimal cushioning, minimal heel-to-toe drop, minimal arch support, minimal midsole.  So the question is, how are they different? Because if you think you're just going to put a pair of partial minimal shoes on and run like you're barefoot, if that's your goal,  to try to be similar to barefoot running but have protection, these studies are interesting. So this is a true minimal shoe.  They compared it to the mechanics of running in the Nike Air Pegasus versus barefoot, and they found indeed that you do run very similarly in those shoes.  When you go to a partial minimal shoe, this is a different study. These two shoes have some midsole to them.  Clearly the Nike Free doesn't have much arch support, but it does have cushioning. They compared those two shoes to the Nike Air Pegasus, which is your standard shoe and barefoot,  and they found that those shoes running in those shoes was similar to running in a pair of regular shoes, but now you have less cushioning.  So my feeling is if you're going to land on your heel, put some cushioning under it if you want to remain a heel striker. So not similar to barefoot.  Now interestingly, Mike Ryan and Jack Taunton from British Columbia here basically did a study randomizing 100 people into one of three footwear groups.  One group stayed in a pair of traditional shoes. Another group got randomized into a partial minimal shoe and then the shoe on the right being a minimal shoe,  and they trained for 12 weeks for a race. And what they found is the partial minimal shoe had twice as many injuries as the minimal shoe.  They didn't look at mechanics, but they, in their discussion, talk about the fact that they think that it's because the partial minimal people  didn't change their foot strike pattern and likely had greater impacts and less cushioning.  And this is just a video to show you. Again, that's the vertical ground reaction force, and you can see that it is different from running in a pair of regular shoes on your heel  but very similar to barefoot running. So what about the highly cushioned shoes, right, the HOKAs? They're advertised as being a shoe that's going to cushion your landings.  So we actually have looked at this, and we've looked at a group of people who are habituated and people who are novice, and we've sort of grouped them together.  And guess what we found? That the load rate, which is that slope, the steepness of the slope, was actually higher in the HOKA shoe, and the tibial shock was higher in the HOKA shoe.  So when you have a lot of cushioning, you have a tendency to land harder. When you have no cushioning, you train your body to land softer. So is cushioning good for us?  Is that Barco lounger that you sit in where you have terrible posture, is that good for you? I don't necessarily think comfort is always the best thing.  Studies have shown that when you do landings on stiff mats, you have a softer landing than when you do landings on soft mats, you tend to land harder.  So that's just from gymnastics. Here's a study looking at single-leg landings in a pair of shoes that are from barefoot  to a pair of cheap shoes that have no cushioning to a pair of shoes that do have cushioning. And guess what? Stiffness of the lower leg increases with the cushioning,  and stiffness is related to higher impacts. And this has been shown in running, too, running across surfaces. When you run across softer surfaces, you land harder.  So there's a lot of evidence for this. So we do need to properly transition, though, because if you haven't done this all your life, your body's not used to it.  It's just like going to the gym and lifting 100 pounds without training up for that. If you got injured, no one would say, Don't ever do that again. Don't go to the gym.  They'd say, Don't do it that way. And that's my message. And again, I'll talk more about that later. But you have to actually get your patients involved in a strengthening program.  You need minimal shoes if you want to forefoot strike correctly. And I just want to remind you that this is not new.  These are the shoes of Ron Hill, who won the Boston Marathon in 1970. And when I talked to him, 1960, I think it's 1970. That might be a typo.  But I talked to him personally, and he said, Maureen, I don't know what all this minimal footwear hype is about because these are the shoes that we were running in.  Those shoes are more minimal than the footwear that we see today. And you have to have a proper gradual transition.  So my new beliefs now through all of this research and through my sort of storms brewing is that for overused musculoskeletal injuries,  foot orthotics should be used as any other brace, temporarily through the acute phase, as in any other musculoskeletal injury, and weaning them off.  Intrinsic muscles do have the ability to strengthen. I'll talk more about that this afternoon. I think we sort of ignore that fact that we have muscles in our feet  and they can get stronger. And we can actually retrain them. This is someone we retrained to activate her arch muscles.  I don't know how well you can see it, but she's got more arch now when she runs. Cushion motion control shoes alter normal loading and may be a contributor to injury.  And I believe the closer we get to our natural state, the lower we have a risk for injury. Now, we've known this for a very long time. I just found this. This is a gem.  It's the philosophy of clothing from the periodical knowledge, and it comes from 1895. Running athletes were unanimous in wanting no raised heels,  that running shoes must be very light, soft, porous, and pliable, and thin as possible, affording the required protection and grip. The foot is nearly free as if bare.  So we've known this for a very long time, and I don't know how we've gotten out of it. So I don't think this is a new trend. I think this is returning maybe to an old one.  This is Billy Rogers in Peter Cavanaugh's lab around 1970.  He is running in very minimal shoes, and he is running on the ball of his foot. I just want to provide you these resources.  These are two special issues on barefoot running, minimal footwear, that cover some of the things that I talked about today.  I need to acknowledge my funding sources, and thank you for your attention. And I know we're not going to have time for questions today.  I'm willing to stay a little bit after the session, and we will have a discussion in the research session. Thank you.

Video Summary

Dr. Irene Davis, an expert in human movement biomechanics, discusses the evolution of her thoughts on footwear in a presentation. As a Ph.D. student, she studied the effect of foot orthotics on patellofemoral motion. Her research focuses on the relationship between lower extremity structure, mechanics, and injury, as well as the effects of minimal footwear on mechanics and injury.<br /><br />Dr. Davis found that excessive rearfoot motion in runners led to increased knee flexion, internal rotation, and valgus, which could contribute to anterior knee pain. Her initial thought was that orthotics could correct these mechanics and reduce injury risk. However, her research later challenged this belief, as she found that pronation is influenced by footwear.<br /><br />Dr. Davis also explored the impact of foot strike in runners. She observed that most runners land on their heels, resulting in higher impact forces and greater risk of injury. However, forefoot striking leads to lower impact forces and can reduce the risk of knee injuries.<br /><br />She also delves into the history of footwear and its relationship to running injuries. She questions the effectiveness of motion control and cushioned shoes in preventing injuries, and suggests that footwear should mimic natural foot mechanics and provide minimal support.<br /><br />Dr. Davis concludes by emphasizing the importance of a gradual transition to minimal footwear to allow the body to adapt and strengthen the necessary muscles. She believes that returning to a more natural state and closer to barefoot running can reduce the risk of injury.<br /><br />Overall, Dr. Davis's presentation challenges traditional beliefs about footwear and highlights the potential benefits of minimal footwear in reducing injury risk.

Asset Subtitle

From Orthotics to Minimal Footwear: An Evolution of Thought
Irene Davis, PhD, PT, FAPTA, FACSM, FASB

Asset Caption

From Orthotics to Minimal Footwear: An Evolution of Thought
Irene Davis, PhD, PT, FAPTA, FACSM, FASB
Dr. Irene Davis is a professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School and director of the Spaulding National Running Center. Her research focuses on the relationship between lower extremity structure, mechanics, and injury, and extends to the development of interventions to alter faulty mechanics through gait retraining. Her interests also include the effect of minimal footwear on mechanics and injury.

Meta Tag

Year Published 2017

Keywords

Dr. Irene Davis

foot orthotics

minimal footwear

pronation

foot strike

running injuries

barefoot running