The Running Shoe Industry Part 2: Where do we go from here and the problems with Running Form research.

It’s easy to point out problems. It’s harder to come up with solutions. In this post, I’ll give my take on what to do with all of the information discussed in the last post and then end with a topic that needs to be covered: understanding the limitations of running form and shoe research.

Running Shoes:
It’s obvious that form and shoes are connected. One of the problems in the running shoe research is that it’s based on heel striking, which we now know is partially caused by the raised heels of many of today’s modern shoes. So we get results that say cushioning improves economy and retards impact forces. That sounds great, but it only does that when heel striking. If you strike midfoot, then all those things improve even more. This is but one example. Here are the pertinent questions that need to be asked and answered:

1. How do we classify shoes?
It’s obvious that the old motion control/stability/cushioning model holds little weight scientifically or practical, so how do we classify shoes for selection? Contrary to the belief of some hard core minimalist, there are differences in the structure and function of the foot that need to be addressed. Just like not every runner can or needs to run 100mpw, not every runner can survive wearing racing flats.

My preliminary suggestion is that classification should be done based on barefoot foot strike. If you heel strike barefoot and plan to keep doing that, then you need a shoe with cushioning in the heel. If you midfoot strike barefoot, then give you a shoe that still allows you to midfoot strike but offers a varying level of cushioning and protection.

2. What do impact forces actually mean?
We used to think the big impact number meant something in regards to injury. Well that hasn’t turned out to be true. Now we think the rate of that vertical impact, called the impact transient is important. In heel striking that transient is higher, and some good data shows a correlation with greater impact transient and injuries. But the bottom line is we know little of what those numbers actually mean. We need to make some sense out of the measurements we take and see if they are actually useful and provide meaning.

3. What makes people respond differently to shoes?
In a study by Nigg (2001), he found that when subjects were tested for economy while running in a shoe that had an elastic heel or a visco elastic heel the results were rather interesting. Some subjects had better economy in a elastic heel, while others had better economy in a visco-elastic heel. The question that needs to be asked is why? Why do runner’s respond differently to the property of the cushioning?

4. Why do we tend to heel strike when fatigued?
Various studies show that a lot of runners convert from a mid/fore foot strike to a heel strike when fatigued at distances ranging from 1 mile up to the marathon. The question is why?

One possibility is that stride length tends to decrease with fatigue and runners are trying to compensate by lengthening their stride, but instead of doing it by pushing off and covering more distance, they simply let their lower leg reach out. Another possibility is that fatigue may impact fine control of the lower leg. As fatigue builds up, the body tends to ignore less critical functions, so the sensory feedback that tells the higher motor centers that we are heel striking are filtered out and ignored. While early on, the brain paid attention to the feedback and didn’t want us to heel strike so that injury was avoided; under heavy fatigue the body is more worried about protecting critical functions so impact forces due to heel strike are seen as unimportant. Lastly, in a surprising twist, our body could make us heel strike subsconciously as a way to slow us down. While this seems contradictory, on a subconscious level it knows that if we slow down fatigue will start to dissipate, therefore heel striking might be a sort of protective mechanism when we are venturing too far away from homeostasis. This question needs to be resolved. What’s interesting is that the top runners don’t seem to alter their mechanics to the heel strike. They tend to maintain mechanics much better.

5. What actually causes injuries?
This is a loaded question so I’m not going to be able to do it justice, but we need to figure out what causes most injuries.  As pointed out in Nigg (2001), the total impact force idea which states that impact forces are major causes, has led to little improvement in injury prevention from a shoe standpoint.  So a better model needs to be developed.  Common sense says impact has to play some sort of a role, but perhaps it’s not total impact or the rate of the forces, but instead what happens during fatigue?  Our body might be fine with dealing with those impact forces during normal running, but be ill equipped under fatigue.  Another potential mechanism is mechanics.  A lot of good recent research has looked at the relationship between certain types of mechanics and injury and I think this a good thing to explore.

Where I think the shoe industry should go:

Many minimalist believers would have us get rid of all cushioning and have all shoes be a zero drop shoe. This is a mistake. It’s the same mistake that was made in going all heavy cushioned shoes. There is likely a balance point in between the all or none offerings.  In an email with former Boston marathon champ Amby Burfoot, he pointed out that the shoe industry is like a pendulum.  For far too long we were too far in the heavy cushioned side, and we don’t want to make the mistake of swinging too far into the complete opposite side.  I agree completely and there is likely a balance, or a happy medium, in between.  As I’m fonding of saying, whenever a new trend occurs, we tend to go too far in that direction, before it settles down into its rightful place.  Let’s not make that mistake in running shoes.

Why do we need some cushioning? Possibly for fatigue resistance. Our body has a natural built in cushioning system in that we alter muscle activity to adjust the impact based on feedback. However, as we fatigue, it’s likely that these natural cushioning systems don’t work as well. It could be due to the lower leg muscles themselves being tired or because the body stops paying attention to the feedback from the lower leg under heavy stress because it is concerned with what is going on elsewhere. It’s possible that having some cushioning to supplement, but not overwhelm, the bodies natural cushioning system early on could aid in delaying fatigue. Or, having some sort of cushioning simply could prevent injuries when we continue to press on during a run or race when our natural cushioning is gone (and we start heel striking for example).

The questions that need to be answered are how much is enough, how much is too much, and where should it go? I’m afraid I don’t know the answers. But if I were a shoe company I’d take a bunch of runners who land midfoot barefoot, then have them put on shoes with ever increasing levels of cushioning and heel to toe rise. Monitor the change in lower leg mechanics. There is likely to be a point where the shoe starts to change lower leg mechanics and when you get to this point, you went one step too far in the amount of cushioning/heel-toe drop. As far as where it should go, I’ll cover that shortly, but one question that needs to be addressed is does cushioning in the fore/midfoot area reduce the impact transient? Research is mixed on this subject, but it could have more to do with where the cushioning is traditionally placed in shoes or the types of materials used. One study I looked at found that 1 out of 3 material reduced the impact transient when midfoot striking. That shows that we might need a different material, than is traditionally used in heel cushioning systems,in the midfoot/forefoot area to provide cushioning.

I also think shoe companies should pay more attention to how the foot function changes during the stride. More research should be done based on how a shoe alters mechanics. Right now shoe companies and research looks at how shoe types change GRF or center of pressure data. Recent studies have shown that how the foot lands or the mechanics of the lower leg change both of these data sets to a much larger degree than any cushioning or shoe manipulation. What that tells me is that foot mechanics should be most important, with shoe manipulations of secondary importance. Companies should look at how there shoes change joint angles, velocities, etc.

This is one reason why I think classifying based on footstrike is needed. I understand and believe that heel striking is not desirable, but let’s be realistic in that some runners aren’t going to take the time to change. Look at the center of pressure and anterior/posterior GRF data of the three foot strike types and you see a completely different picture. A heavy heel striker needs some cushioning in the heel that is soft enough to absorb the impact. A light heel striker wouldn’t need such soft cushioning as someone who lightly heel strike generally hits the heel but is quickly flat foot. For both of these types of runners, the foot has a more distinct back to front absorption and propulsion phase, so some of those nifty propulsion systems companies have designed might make sense. But for midfoot and forefoot runners, they make zero sense.

A midfoot striker on the other hand usually lands on the outside of the foot under the arch and then moves medially. So you’d have to have some sort of durable material on the outside that might provide a slight amount of cushioning. The medial and front side of the shoe probably needs to be a harder material with good grip because the majority of the propulsion will take place in this portion. For forefoot strikers, the heel is almost useless. Little cushioning needs to be there, though it should have just enough of a heel so that the runner puts the heel down instead of holding it off the ground. The shoe should probably be zero drop and have some sort of minimal cushioning in place along the outside metatarsals that spread the impact over the foot, instead of localizing it here. Lastly, all shoes should be as light as possible given the above requirements.
One of my favorite spikes was the Nike Kennedy’s. Take a look at these spikes and you’ll note that they only have spikes on the inside. Why? Because that’s where a distance runner pushes off, and when you need the most grip because the posterior forces are the highest! More ideas like this looking at the function of the foot would be good.

Nike Kennedy’s:



The bottom line is that shoe companies should design shoes that let the foot function. It should work in concert with it, not in opposition. And the shoe should allow for individual biomechanical differences..

Research Problems

Lastly, I’d like to end with the problem with evaluating running form in research studies. This is originally part of an email I sent to Pete Larson and he suggested I post it so I am. It fits well in this post, because it once again demonstrates that we have to be careful with how we evaluate research and be smart about so that we don’t end up in a situation like we have with running form or running shoes. The email below was originally in response to a Matt Fitzgerald article that can be found below:


Ask The Experts: What’s Your Take On POSE And Chi Running?

The problem with scientific research on running form changes are:

1. The studies are short term. Most are a few weeks to max around 10wks at length.

So, we are going to go dramatically change someone’s stride from what they’ve been doing for the past 15-20years+ in most cases in a matter of weeks and we expect that the body will rapidly adjust, resync all the neuromuscular firing patterns and be magically more efficient? Of course this doesn’t happen. Most of the time when you make a form change the acute effect is that efficiency gets worse! Why? Because, it’s awkward and new. Your body has to go through a whole period of adjusting everything from the neural signalling, to motor unit recruitment, to who knows what. We’ve all experienced this. When I was a younger soccer player, I had to learn to kick with my left leg. At first I felt totally uncoordinated, but I kept at it and by the end of my soccer career I could kick with my left leg pretty much as good as my right. Do your own experiment and go try and write with your left hand. It’s hard, but if you do it for a while you’ll get a lot better. My contention is that in an acute setting, efficiency will decrease or stay the same, but in the long term, the ceiling for efficiency is higher.

2. The measurements used.
There are so many different ways to measure or express running economy, and I think most are flawed. First, we are using oxygen consumption to represent energy expenditure, which might not be the best case. For instance look at the graph below from Kyrolaine (2001) that compares Oxygen consumption, calculated energy that takes into account anaerobic sources, and energy expenditure. As you can see, even at low speeds, there’s already a gap between oxygen consumption and estimated energetics. At faster speeds, it’s almost useless if you don’t correct.


Second off, economy is either expressed as VO2/distance, VO2 at an absolute speed, or in terms of caloric cost. If you look at the literature, all give vastly different results. For example, the traditional VO2 measurement usually shows fast runners (who generally have a high VO2max) with worse economies than slightly slower runners. Just from a practical standpoint that doesn’t make a whole lot of sense. While caloric cost shows that better runners have better economy. Finally, the name of the game is to cover a given distance as fast as we can, so a lot of misinterpretation happens when we look solely at economy measurements.

3. Efficiency really is three things rolled into one. Biomechanical, Neural, and Metabolic efficiency. When we talk about running economy, we are talking about a gross measure that kind of represents how all three work together. It’s one reason why people who look bad running, can still have pretty good efficiency. If they’ve optimized two out of three that contribute to total efficiency, they’re going to be pretty dang efficient.

All that being said, in Fitzgerald’s article most of the study results make sense if you recognize the above two things. For example, of course economy would get worse if we consciously tried to think about it. What happens when you do that? You start forcing things to happen and it’s not natural. You are forcing your body to think about running in a slightly different way. That’s why you do that in practice to ingrain it so you don’t have to think in a race! Look at other sports. They consciously think about the action when working on it in practice, then instinctively do it in a game. For example, in tennis, you work on your serve in practice by tweaking the mechanics of it, but in the game you are just doing it, relying on what you learned in practice to take over.

Lastly, as for the findings by Stephen Mcgregor. It just confirms what we already know. You get more efficient at running by….running. If you go run 100 miles a week, your body will figure out how to maximize it’s efficiency of whatever stride you are using. My contention is that if we have a biomechanically correct stride, the ceiling is higher. Why? Because we know certain actions have to be mechanically more efficient. If we can maximize biomechanical efficiency, then put a lot of training under our belts while running that way, we’ll reach a higher level of efficiency then if we just ran with bad biomechanics but maximized our efficiency at running with bad biomechanics.

The problem isn’t the research; it’s the human element, the interpretation.


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    1. RICK'S RUNNING on September 27, 2010 at 4:20 pm

      I think the type of foot you have makes a big difference to the amount of padding in the shoe needed.
      I have quite a high rigid arch and a very minimal shoe becomes painful after an hour.
      Someone with flat feet might need far less padding.
      i think they need to look far more into how different foot types react and make forfoot striking shoes to match.

    2. Pete Larson on September 27, 2010 at 5:15 pm

      Great post Steve. You make a great point about the fact that a lot of the scientific research out there on running is based on heel striking. I can't tell you how many studies I have read where in the methods they point out that midfoot and forefoot strikers were excluded – so much of this work needs to be redone looking at the entire spectrum.

      Another thing to keep in mind with regard to scientific studies is that all conclusions are based on statistical analyses, and variation is rampant. Even if a comparison yields a statistically significant result, there may be individuals with each sample that don't follow the predominant pattern. In other words, a study might shoe that statistically, midfoot runners have lower peak GRF, but that does not mean that every midfoot runner in the study had lower peak GRF. We wind up comparing what we hope are normal distributions, but there are always going to be people that fall out into the tails of the distribution. That may not be a big problem if you are studying something like foot size, but when it's a measure that could impact injury susceptibility, even the runner's in the tails need to be accommodated.

      Regarding the last point, that's why I think greater variation in shoe design is needed. Currently, shoe companies try to make a generalized shoe that will fit the needs of as many runners as possible (probably for cost reasons), but may be ideal for only a small fraction of that total population. Imagine if we tried that same approach with eye glasses…


    3. marathonmaiden on September 27, 2010 at 6:09 pm

      another great post. i completely agree with you that as trends come up it seems to become the only "right way" to do things. i think that there are so many different ways to be right in terms of shoes and cushioning etc.

      i'd like the running shoe companies to make more variety in shoes (like an above commenter said). there is so much variety with humans in the first place so to assume that a one type fits all approach is the best is really silly. couple that with "extreme" trends and fads and it is likely the recipe for a disater

    4. Ryan Miller on September 27, 2010 at 6:17 pm

      I'd love to see some studies that look at the effects of the fit of the upper. For example one theory is that a narrow toe box will limit stability and lead to excessive pronation because the great toe cannot support the arch. The majority of the studies are on the sole unit, we rarely ever look at upper fit. I feel the proper functioning of the toes, allowing them to splay out is a critical piece that should be examined further.

      This might be way many people resonate with the five fingers. They intuitively know that allowing the toes to splay out is a good thing, and having the individual toe pockets is a visual cue for that.

      Most minimalist runners are looking for a shoe with an extremely wide toebox for this very reason. I'd love to see some studies done examining the effects of this.

      In my own personal 'study of one' I've taped my toes together and run around for a bit. After that experience, I can see why allowing the toes to splay is a good thing!

    5. Tuck on September 27, 2010 at 6:39 pm

      So in a nutshell, we know very little about what actually works best for a runner as far as shoes go.

      That's kind of sad…

    6. Andy on September 27, 2010 at 7:03 pm


      I think you're a bit hasty to follow the Amby Burfoot path of "surely we need *some* cushioning". I applaud your hesitance to go to the other extreme, but I'd contend that it is THE open question, given the data. Do we need cushioning? Really? How much and where and when?

      It could very well be that injury is best prevented by maximizing feedback, which entails minimizing cushioning. It could be that a bit of cushioning allows us to push our bodies faster than they would normally go, but at the expense of a higher injury rate. Let's ask the question. We likely won't end up doing away with running shoes altogether, but we could very well end up with something more effective and drastically different that what most are running in today.

      Otherwise great post. Many will refuse to take a step back to change their form and take two steps forward, but if we have footwear options, the interested among us can do our own experiments.

    7. RunningPT12 on September 27, 2010 at 7:19 pm

      Thanks for the post – as always, very well thought out.

      My only other thoughts/additions are 1.) another problem with running gait research is that a chunk of it is done using treadmills versus roads, 2.) some of the research is done using self-selected paces rather than examining runners at a set pace.

      One other thing – this whole idea that just because one is barefoot that they're automatically going to adopt a midfoot landing has just been taken too far. My own experience is that slower, less well conditioned runners when barefoot have varying styles of footstrike – some of which are rearfoot (I've plenty of video from gait analyses showing this).

      Again, thanks Steve,


    8. Robert Osfield on September 27, 2010 at 8:25 pm

      Another intriguing post, thankyou. In particular I'm left wondering just why some runners progress from forefoot/midfoot landing to a heel landing when fatigued.

      Could it be that runners are varying the balance of muscles groups that using when under fatigue, giving some rest while others take the strain. So when quads and calves are tired from landing with knee bent and on the forefoot, the body starts landing with a straighter leg to rest them. A study into which how much different muscles groups are being used throughout a run would be interesting.

      It also occurred to me that much of modern running involves much more monotony that we were evolved to handle. Our ancestors will have walked, jogged, ran, sprinted, jogged, walked, stood, sat, dug, climbed, mixing up the use of many different muscles groups at different levels of intensity. Contrast this to both training and races done today – the pace and surface are often very regular and very artificial with it. Could it be that mixing up pace and running form might be a good means of rest different muscles groups that the body naturally will be inclined towards? I don't have any answers to this, but it might add another avenue to research.

      One statement in your post struck me as out of place:

      "Many minimalist believers would have us get rid of all cushioning and have all shoes be a zero drop shoe. This is a mistake. It’s the same mistake that was made in going all heavy cushioned shoes."

      I think it rather premature to say no cushioning and zero drop is a mistake. I don't recall any research papers you have discussed suggestion this. From your post your assertion seems to be based on an "intuitive" principle of extremes are invariably wrong and that some happy medium will be right. It's hardly scientific approach though.

      Clearly more research needs to be done on how runners, that have grown up running bare foot/with minimalist shoes or have done to so for a long period, cope with different surfaces, training and races etc. Do they get less/more of different types of injuries? Do they change their running form when fatigued in the same ways that cushion shoe runners have do?

    9. Robert Osfield on September 27, 2010 at 8:34 pm

      Some further thoughts..

      I'd also like to add another observation to the mix. Cushioning can cause instability in the foot on landing – a cushioned platform gives much more than solid ground, combine this with the instability of having a raised heel can make turning over on ones ankle much more likely.

      It's seems like to me that a runner which larger natural pronation will find that this instability will exaggerate the pronation. And what we find is with "Stability" shoes is less cushioning in parts of the shoes whilst still retaining cushioning elsewhere. Might this just be hiding the problem? i.e. that cushioning and elevated heels are particularity bad for heavy pronators? Could removing the excessive cushioning and lowering the heel be the cure to the actual problem?

      Again research needs to be done to answer these questions definitively.

      Funny how sometimes when you look for answers the more questions you find 🙂

      I also wonder about the play between cushioning and force distribution. You can think of this looking at local changes in force on the foot vs changes on the forces on the rest of your body. A small amount of cushioning might help even out the stones on a trail to make it more comfortable on the foot, while too much an you could loose the fine feedback you require from your feet for good balance.

      Another topic for investigation should be amount of flexibility in the sole that different shoes provide. Just how flexible do they need to be? I have a pair of plimsols that are the perfect shoes flexibility wise, grip and cushioning are rather a bit too minimal for my current running form though.

      A little about my own experience – I don't run without cushioning yet. Too much cushioning and poorly fitting shoes have certainly caused me injuries though, from a bruised metatarsal bone from wearing too narrow shoes, to bouts of calf strain/Achilles tendinitis with overly cushion heels.

      The cure for me does seem to be running in less cushioned shoes with less heel raise, and size too large to accommodate my wide feet. I've just binned my Nike Pegasus and replaced them with Inov8 Roclite 315's. With this change a nagging calf injuries have finally started to clear up. I do still wish for more width fittings on the Invo8 range though. Still hunting for that perfect shoes 😉

    10. stevemagness on September 28, 2010 at 2:43 pm

      Thanks for the comments everyone. Now to address them:

      Rick- Agree, we need to look at the differences in the foot.

      Pete-Excellent point. One of my favorite sayings is science is concerned with the average, the coach (or athlete) is concerned with the individual. Just my observation but until recently the shoe options were skewed towards the heel strike/heavy cushioned side, so runners on the opposite side of the distribution were largely neglected. As ridiculous as it sounds, there are going to be those select few who need the Brooks Beast, just as there's going to be those who need no shoe. The key is we need to figure out a way to decide who those runners are!

      Marathonmaiden- Thanks for the post. Variety seems to be the theme and I must say I agree. As I said above, the problem is figuring out what runner needs what kind of shoe.

      Ryan- Interesting take. I've often wondered about shoes that limit the splaying out of the toes. This was brought up to me when discussing VFF's with a sprint coach. He wondered if the individual toe things would let the toes splay when sprinting.

      Tuck- The more I study and learn, the more I realize we know very little about most things. It just goes to show how complex most things are.

      Andy- You're right, that is the unanswered question. My contention with cushioning is based on the fatigue issue. A little bit seems to be needed for MOST people during longer races or else the calves/lower legs become a limiter. Can we train these not to be a limiter, perhaps, but we just don't know how long it takes. For example, Dathan Ritzenhein's recently commentented that his racing flats were too minimal for his half marathon because his calves and lower legs started cramping and affecting his stride. We know he just switched to a midfoot strike, so that makes sense that his lower leg isn't as well trained to absorb the shock. In his case a slightly more cushioned shoe to take the burdon off his body to provide cushioning enhances his performance. The question is how long does it take to train the lower leg to become strong enough not to be a limiter. My feeling on the feedback is that for most of us, a minimal shoe that has just enough cushioning to provide some protection under fatigue, but not too much that it dampens our proprioception is the key.

      RunnerPt12- Great comments. THe form research has a lot lacking. And I agree on the barefoot striking. Go look at Lieberman's famous study and there are barefoot heel strikers. The question is why?

      Robert- I think the heel striking when fatigued is one of the interesting unanswered questions.

      The great Hungarian coach, Mihali Igloi suggested that we have several different stride types (he called them long and short swing) that we should use to alter the muscle recruitment. He'd train his runners to be able to switch between these stride types when fatigued to try and maintain performance. It's interesting that most non-competitive runners get locked into one stride/pace, while the more competitive runners seem to run the gamut from sprinting to jogging. I think more recreational runners could learn from this.

      My statement on 0 drop, no cushioning was to get across the point that it's dangerous to go to the other extreme without exploring the option. It would be an overreaction in my opinion. It might turn out to be the answer, but we should rigurously test the idea and theory before jumping into it like we did with heavy cushioned/elevated heels. I'm fine if that's the answer, but my point was that lets take the time to research it and think about it.

      And you are right. I think we've brought up more questions than solutions! But that is good, because before this discussion many just accepted things the way they were, but now we've got people questioning why X is in a shoe and they desire an answer besides "it's always been there."

    11. Paul on September 29, 2010 at 4:37 pm

      Great article, thanks for writing!

      Let me ask a question….given the swing toward minimalist shoes….how often should one replace shoes?

      I would think running on very gradually more worn shoes (that have become more flexible and less cushioned) would actually be heading toward more minimalist.

      Of course, at some point you probably need a new pair, but perhaps a very worn pair isn't as dangerous (for some) as made out to be in the past?

      What are your thoughts?

    12. RH on September 29, 2010 at 4:40 pm

      Just a thought: Perhaps the fact that midfoot strikers land on the outside of the foot and heel striking under fatigue are connected.

      A midfoot striker absorbs part of the impact by a controled movement from the outside of the foot to the inside. This movement is controled by the Tibialis and Peroneus muscles.

      Heel striking is the same mechanism, turned 90 degrees. When the muscles that control the inward to outward movement of the foot tire, a runner can recuit a similar cushoning mechanism that uses two fresh shin muscles, the Extensor Hallucis longis and Extensor Digiotorum together with the calf muscles.

    13. Johnny D on October 1, 2010 at 5:53 pm

      Hi Steve, great post.

      I've been doing a lot of reading in the scientific literature lately, trying to see who, if anybody, has tackled these big questions. One thing that you left out was the role of proprioception in impact moderation and footstrike. There has been some really interesting work done looking at how the foot "knows" where it is. Waddington has done some research on using textured insoles, which seem to increase the foot's sensory awareness. One researcher proposed there is an element of "essential noise" that running barefoot (or with a textured insole) provides that allows the foot to know "okay, here's the ground, and here is where I am relative to it." Waddington was actually building off work by Isamu Wantabe, who published a very interesting paper on textured surfaces and body sway in 1981.

      Benno Nigg, who I think you mentioned in the post, has done extensive work on how the body controls motion while running. He has forwarded a "new paradigm" on pronation, which states that, in reaction to impact forces, the body reacts by pre-tuning muscles so that the next footstrike will follow the body's "preferred movement path." So what he says (and claims you can measure using EMG studies) is that if a runner pronates and you stick him in a medially-posted shoe with pronation-control orthotics, his external shin muscles (peroneus longus and others) will simply activate more to counter the antipronation properties of the shoe/orthotic. A few review studies have found that orthotics and other pronation-control devices have an "insignificant, non-systemic effect" and aren't as great as we thought they were. Nike seems to have picked up on the role of impact forces and proprioception–in 2006, they patented an insole that had one half–either medial or lateral–smooth and the other half bumpy. The idea was to modify footstrike and pronation by selected stimulation of the plantar mechanoreceptors, which is something we will likely hear more about in the next 5-10 years. Curiously, I haven't seen Nike put this product on the market yet!

    14. Johnny D on October 1, 2010 at 5:53 pm


      As far as the comments on cushioning causing instability, the claims just aren't substantiated. There IS evidence that shoes that are too soft (below about shore hardness 30A) will "bottom out" when compressed, and cause a larger ground reaction force, but a pretty large range of hardnesses is "acceptable" by the body. I also suspect the cushioning properties of shoes aren't too far from those of a nice soft grass field or mondo track, and nobody blames those for causing instabilities.

      Also, I'd like to point out that, though Lieberman characterized the impact transient rather eloquently in his Nature article, the big weakness that still exists is that we do not know how GRFs translate to actual forces inside the body. It's rather easy to model the impact transient, as you can just treat the leg like a bunch of passive springs–the millisecond-range of the impact transient is far too short for muscular action to be of any concern–but once the active phase begins, all bets are off. One study I saw, called "internal forces at chronic running sites" I think (sorry, don't have author right), used a model to show that impact forces at places like the plantar fascia, achilles tendon, and patellar tendon were much greater during the active phase than the impact phase. So clearly somebody's got to get a clever idea as to how to solve this. My clever idea is to have a runner run through a hallway-shaped fluoroscope, so the researchers would have accurate, real-time data on how ALL of the bones in the body were moving throughout the gait cycle. Only problem is that nasty x-ray exposure…

      To my knowledge, there HAVE been studies on biomechanical changes due to fatigue, but it has been either "peripheral fatigue" (doing ankle circles between bouts of fast running, for example) or metabolic fatigue–running to exhaustion. No one has looked at biomechanical changes in relation to SPECIFIC muscular fatigue. I'd like to see a study that took 30 or 40 trained athletes, had them do a 1.5 or 2 hour run on a treadmill (or a track with a high speed camera and markers) and study the "classic" biomechanical markers–tibial shock, dorsiflexion, ground reaction forces, hip extension angle, etc.m and see how they change as the athlete experiences muscular fatigue.


      -Johnny D

    15. Robert Osfield on October 3, 2010 at 4:24 pm

      Johnny D. wrote: "As far as the comments on cushioning causing instability, the claims just aren't substantiated. "

      Perhaps one should try doing a fell race in highly cushioned shoes and then tell us if they feel as stable as a shoe with minimal cushioning…

      The high elevation and elasticity of highly cushioned shoes both reduce stability, combine the two and it's pretty fatal combination for the ankles on uneven ground. It's a straight mechanical property, whether your driving a car round a bend or running in a shoe the same physics applies, the greater the cushioning the less stable the system is.

      If you are pronating excessively then my guess is that you are sitting much closer instability as your ankle is already more rotated on landing. It's doesn't take much imagination to see that elevation and cushioning are going to be a particular problem to such a runner especially if they meet uneven ground.

      I'd guess there will not be too much literature on analysis of running on really uneven ground, but this doesn't mean that hundreds of thousands of runners aren't regularly going outside the envelope of literature. Where running literature is too limited we just have to extrapolate what is known about mechanics of stable and unstable systems.

      The relationship between higher elevation and greater elasticity leading to a less stable and potentially unstable system is obvious to any engineer. Go ask anyone who's designed a bridge, building, car…. so rather than unsubstantiated it's basic principle of mechanics.

    16. Anonymous on February 25, 2011 at 2:47 am

      i don't think we should all go zero drop suddenly, however, i am a barefoot runner, and i think the transition needs to be made
      of course, cushion in some ways helps when you're recovering, in my opinion, not so much when you're running

      i started barefoot running last august to make my senior year in high school right
      and boy i'm a lot stronger

      but as for heel strikers and midfoot strikers
      hell strikers shouldn't be encouraged to continue it, this is why a lot of my teammates get shinsplints so fast, landing on their heel and developing funny running habits
      although i never got shin splints from running
      (hurdling doesn't count, although now i land almost strictly on my forefoot, with an accidental heel sometimes)

      my point is that i don't think anybody needs stabilizing, if your toes are crooked, they should be corrected, and crooked toes are about the only major footproblem in my opinion
      preventing natural movement isn't good

      -cody r.

    17. mmilton031 on May 30, 2012 at 5:10 am

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    18. mmilton031 on May 30, 2012 at 5:20 am

      Congratulation!I've been looking for a new running
      insoles for my athletic footwear, and these shoe inserts
      look really comfortable! I have concerns with this problem
      and I'd be considering seeing how they perform for my feet!
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      running insoles

    19. Anonymous on July 29, 2012 at 11:25 pm

      Steve, overall I really like the article, but I feel the need to point out one possibly major issue with the spike shown (Nike Kennedys).

      Placing all the spike wells on the medial side of the spike plate is probably not advisable because the foot acts like a tripod with the heel, first, and fifth metatarsals acting as legs (to the tripod).

      Because the fifth metatarsal is a major point of weight bearing, lack of a spike well on the medial side can result in slipping (see this link on the issue).

      This might not be an issue for someone of significant forefoot valgus, but people who are either flat across or varus (like myself), this is probably an issue.

      Just thought this should be put out there.

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