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I’ve been following with interest a spirited debate that is taking place over on my friend Bill Katovsky’s Zero Drop blog. Like me, Bill is an advocate for greater variety in shoe choice, and his approach on his blog is to poke fun at the status quo in addition to providing the occasional shoe review. He also has published a number of interesting guest posts – his blog is well worth a look if you haven’t seen it already.
Anyway, yesterday he posted a comment by ASICS head of research Simon Bartold in which he essentially refers to the minimalist running movement as “nonsense,” and says this about ASICS future running shoe plans:
“We (ASICS) are now working on a training shoe that is less structure and lightweight, but still offering stability and holding true to a rearfoot srike pattern design. I have based this on the premise that, no matter what is being said about technical running footwear, there is no evidence that it really 'aint broken, so we will tweak, but no need to fix. The minimalist movement works on the premise that by reducing heel height, i.e. the overall gradient, by maybe 6 mm, it induces a midfoot or even forefoot strike pattern. I have not been able to identify one single piece of credible evidence to support this.. so.. we will stick to our guns. Once more the ether is thick with unsupportable nonsense. pose, chi, toning, barefoot, minimalist....when will it end?”
Based on this comment, ASICS appears pretty content to avoid following its major competitors (e.g., Saucony, New Balance, Nike and soon Brooks) into the minimalist fray. To be honest, I don’t really care if they do – there are plenty of options out there nowadays from other companies, and it’s ASICS loss if the movement continues forward and they lose out on a growing sector of the running shoe market (according to Leisure Trends Group, minimalist models made up 39% of all trail shoes sold in April 2011 – they accounted for only 3% in 2010).
The comment above is not why I decided to jump in and write this post. Rather, my reason for doing so is to respond to a comment posted by Bartold in response to what Bill published on Zero Drop. In his comment, Bartold challenges Katovsky to provide scientific evidence for any of the claims he has made, and states “there will be no evidence.. because you have none.” This is where my interest began to pique. Let’s take a look at what Bartold has to say, and see what evidence might in fact be out there.
“Firstly, your photo caption erroneously states ” if Asics had its way, all runners should be perfectly content to continue as over-striding heel-strikers.” Not sure where that came from, certainly not me. I beleive some runners should forefoot strike. for example, if one has less than 10 degrees dorsiflexion, which many runners do, that runner cannot achieve heel srtike. But you know what.. humans are very varied, and lots of runners heel strike and run well and efficiently.There is no problem midfoot striking or forefoot striking in an ASICS shoe.. I recommend it all the time, especially if I think a change in form will help. But not to everyone.”
OK, first, the bit about 10 degrees of dorsiflexion. I’m no podiatrist, but I’ve watched slow motion video of a lot of runners (thousands), and almost every one wearing a typical shoe with a ~12mm heel lift and extensive cushion is a heel striker (this data is working its way through peer review as I write this). You can look at the photo in Bill’s post or the photo to the right and see that the sole of the shoe is virtually perpendicular to the lower leg just prior to contacting the ground. Assuming that shoe has a 12mm heel lift, it’s quite possible that the foot inside the shoe is actually plantarflexed at heel strike. Furthermore, the runner in the photo above could plantarflex the foot a heck of a lot more and still be landing on the heel – that’s what overstriding will allow you to do. So, I’m not quite sure where that 10 degree figure comes from. Perhaps I’m just misunderstanding what Bartold is saying, but then I’m just a lowly blogger.
Bartold then discusses that he believes some runners should forefoot strike, and I agree. Some people will naturally forefoot strike in any shoe you give them, just as some people will continue to heel strike even when you take their shoes off – see Daniel Lieberman’s 2010 Nature paper for evidence of this. However, both cases are rare – forefoot striking in lifted shoes is not common, just as heel striking barefoot is not common. I also agree that many runners do just fine heel striking, but anecdotal evidence (and I get a lot of it) suggests that others do not, and that moving to less shoe can be of great benefit. Does everyone need to go minimalist? No, absolutely not. If you are running pain free in ASICS 2100 series shoes, by all means, keep doing so. Being able to run is what is important after all, and why mess with what’s working. However, as Bartold points out, humans are variable, so why should we expect the 12mm lift, heel strike model to work for everyone? This is why I’m so perplexed at his willingness to fight the minimalist movement. If some people are benefiting it, why all of the resistance? Sure, ASICS makes racing flats that are similar to many minimalist shoes, but good luck to the recreational runner who wants to find a pair to try on and doesn’t have access to a specialty running store. It’s pretty darn unlikely that you’ll find the Piranha or Hyperspeed at your local Foot Locker or Dick’s Sporting Goods. Until recently, the average runner has had little choice but to go with the 12mm lift, heel striking model. Thankfully, progressive companies like Saucony, Merrell, Altra, Vibram, and New Balance are bringing alternative options to the running masses.
To be honest, I’m also quite skeptical that midfoot or forefoot striking in a 12mm lift shoe is a good thing. To accomplish a forefoot strike in a shoe with a big heel lift requires quite a bit of plantarflexion upon ground contact to clear the heel. Since evidence seems to be a popular word in this discussion, what evidence is there that this is safe? Shouldn’t the burden of proof be on the company making the product to show that it’s safe for the consumer? Isn’t this what drug companies have to do?
Moving along, Bartold next says this:
“Sorry Zero Drop.. you are misleading your bloggers.. you state “Most conventional running shoes have an average drop of 12 mm, which places too much impact and stress on the heel region”. Nonsense.. show me the proof.. published in a peer reviewed scientific journal.”
As I have written previously here on Runblogger, forefoot striking has been shown to reduce vertical impact peak (many studies, Squadrone and Gallozi, 2009 and Lieberman et al., 2010 are recent examples) and vertical impact loading rate (Oakley and Pratt, 1988; Williams et al., 2000) relative to heel striking. Data showing no difference between forefoot and rearfoot impact loading rate is out there (e.g., Laughton et al., 2003), but data are limited that involve people well acclimated to multiple landing types. Data on loading rates are sometimes difficult to interpret if runners are not acclimated to a barefoot running style – for example, De Wit et al., 2000 showed dramatically increased vertical loading rate in barefoot runners compared to shod runners, but their barefoot runners were heel striking. One would fully expect a barefoot heel strike to exhibit a higher loading rate since little cushion other than the heel fat pad is present to slow down force application. Lieberman et al., 2010 showed that habitually barefoot runners overwhelmingly land on the forefoot, which suggests caution when interpreting studies of barefoot heel strikers (who were probably unaccustomed to running barefoot). See this recent (2011) paper by Jenkins and Cauthon in the Journal of the American Podiatric Medical Association for more on this issue.
Why does any of this matter? Higher vertical impact loading rates (how fast impact is applied to the body – think punching a wall with your bare fist vs. a boxing glove) have been linked to injuries like lower extremity stress fractures (see this review paper by Zadpoor and Nikooyan, 2011). Conversely, Nigg, 1997 reports results of what appears to be an unpublished graduate thesis suggesting that impact force and loading rate are not linked to injury, and that increased loading rate was actually associated with fewer injuries. However, this analysis looked at short term injuries and did not look at injuries by specific type.
Next…
“You further state “The runner’s cushioned heel strikes the ground first instead of the shoe landing on the more biomechanically efficient midfoot or forefoot”.. again.. show me the evidence.. let me save you time.. you will not find it because it does not exist. “Excessive heel-striking marks an open-invitation for potential foot and leg injuries. But minimalist and barefoot running shoes have a much less drop. Which means you are now landing on the midfoot or forefoot– the way nature originally intended us to run.”.. balony.. absolutely zero evidence of a connection between heel striking and injury.. and there is no evidence whatsoever that “nature” intended us to run on the forefoot.”
Bartold goes on to cite a reference by researchers from the University of Massachusetts that reports “a 7% decrease in running efficiency in the barefoot group in a model predicting barefoot vs shod running.” I’m not sure exactly which paper he is referring to, but if it’s the one I think it is, it’s a conference abstract in which a computer model was developed based on measurements from a single individual. No oxygen consumption measures from living human beings were involved. So, the two-dimensional computer model based on one person referred to in an unpublished conference abstract ran better on its heels…not sure I consider that to be strong evidence. Jenkins and Cauthon (2011) summarize a number of studies which have shown reduced oxygen consumption in barefoot running compared to shod running. However, to be fair, it’s quite possible that this is simply a mass effect since removing shoes removes weight from the end of the limb. Squadrone and Gallozzi (2009) found oxygen consumption to be lower in in experienced barefoot runners running in Vibram Fivefingers vs. traditional shoes, and noted that running in traditional shoes resulted in significantly greater dorsiflexion of the foot on landing (i.e., they were heel striking, albeit mildly). Interestingly, barefoot was not significantly more efficient than either traditional or Vibram Fivefinger running (i.e., it was in between the two). The efficiency question might just be a wash, but I don’t think we can really say either way with any great degree of certainty at this point.
Studies of efficiency aside, from a performance standpoint (where it really matters), Hasegawa et al. (2007) looked at elite half marathoners and found an increased proportion of midfoot strikers among the faster runners in their sample. Furthermore, my friend Steve Magness reports some data from 800m and 1500m races showing that ground contact time is shorter in forefoot and midfoot strikers, and Hasegawa et al. (2007) showed a distinct relationship between ground contact time and speed (shorter GCT = faster runners).
Magness also makes this relevant point regarding why “nature” might intend for us to land on our forefoot (read his post, it’s well worth it):
“…the Achilles tendon and the arch of the foot store a large amount of energy upon footstrike and then that energy is subsequently used upon take off. A forefoot strike has shown that it potentially uses this mechanism much better. One reason is that upon initial contact the foot is in better position to store the energy from the ground strike. In heel running, a great deal of the initial strike energy is lost. On a similar note, it is possible that a forefoot strike utilizes the stretch reflex mechanism better due to the position of the foot upon contact. With a forefoot strike the whole calf complex is in better position to be stretched and subsequently respond than in a heel strike.”
Granted, this is not peer reviewed, published data, but Magness was recently hired to help coach the likes of Galen Rupp and Kara Goucher, so apparently Alberto Salazar and Nike think he’s pretty on the ball. What’s more, Lieberman’s nature study (2010) showed that barefoot individuals who have never worn shoes overwhelmingly run on their forefoot. Not all of them, but the vast majority. Does this mean that they will do so in every circumstance? No, probably not, but one need only take of their shoes and run down the road to see that your foot strike will change. I’m pretty well convinced that nature intended us to run most of the time on our forefoot.
Finally, I teach comparative anatomy, and this has some bearing on my thoughts about where footstrike should occur. When you look at cursorial (running) animals, what you often find is that over evolutionary time their “heels” have become raised up off the ground. Dogs run on their toes (digitigrade), and horses run on the tips of their toes in the form of a hoof (unguligrade). They do this because it allows them to essentially lengthen their legs, and they have slender distal limbs with many long tendons and ligaments. If one is to believe the theory that humans are/were on a path to becoming distance running specialists, would it not be a logical hypothesis that we were also moving in a direction quite similar to other running animals? We have long Achilles tendons compared to chimps, and an arched foot supported by the plantar fascia. As Magness states above, storage of elastic energy is more effective with a forefoot strike than a heel strike, and most of us will automatically convert to a forefoot strike after running barefoot for a time (sometimes instantly).
Onward…
“You see, you are completely missing the point.. every runner is different and has different requirements based on their biomechanics, their weight, their gender, their physiology etc. You are deliberately espousing a one size fits all approach and telling your readers that if they run barefoot or minimalist, they either will not get injured or will have injury rate grossly reduced.. are you kiding.. fact is, running is dangerous.. 65% of runners will get injured.”
Yes, every runner is different, and does have different requirements. ASICS has a lot of shoes to choose from, just not if your preference or requirement is one without a big heel and lots of cushion. See again my above comment about the likelihood of the everyday recreational runner finding a pair of ASICS racing flats in a typical shoe store. In terms of heel height, ASICS might as well be one size fits all.
And yes, runner’s will always get injured, and we will do so because we are often dumb and run more than we should and when we should not. However, in the absence of clinical trials, which ASICS has not published in a peer reviewed journal to show that their own shoes reduce injuries, we rely mostly on anecdote. Anecdotes suggest that some runners benefit from a barefoot or minimalist approach. Why ignore this? If you believe that humans are variable, why is the 12mm model so ubiquitous in the ASICS shoe lineup. Where’s the evidence?
“I challenge you to provide me with ONE single piece of evidence, published in a peer reviewed scientific journal to support the concept that there is a proven benefit to lowering heel gradient.
He asks for ONE piece of evidence, so here’s one. Again to Squadrone and Gallozzi, 2009. Running in zero drop Vibram Fivefingers compared to traditional shoes reduces oxygen consumption and reduces ground contact time (which has been shown to be associated with greater speed). Maybe it’s not a perfect example, but the claim that there is NO evidence is false. We can turn this around and ask for peer reviewed, published evidence of a benefit to running in ASICS shoes. What is the benefit of a 12mm lifted heel? You’ll typically hear about reduced Achilles problems, but has this been proven? Richards et al., 2008 state that “…the overall impact on injury rates of running in a shoe with an elevated heel remains untested in clinical trials.”
Fact is, this type of argument won’t get us far, because neither side has a whole lot of published evidence right now.
“Improved mechanics and muscle function? Nope.. Chockalingham et al 2011.. no change to gait kinematics or muscle function when changing from heel strike to forefoot strike.”
Last time I checked, a change in footstrike is itself a kinematic change. I was unable to find this reference anywhere, so hard to evaluate it, but kinematic changes have been shown many times between rearfoot and forefoot strikers. For example, consider this statement from a conference abstract by McClay and Williams, 1998 (published later in the Journal of Applied Biomechanics as Williams et al., 2000):
“Significant differences have been noted both in joint kinematics, kinetics and ground reaction forces in forefoot strikers (McClay and Manal, 1995, Cavanagh et al, 1980, Oakley et al, 1988, Harrison et al, 1988). These differences include greater rearfoot plantarflexion and inversion and knee flexion at footstrike and greater peak dorsiflexion and eversion velocities. In addition, larger peak vertical and anteroposterior GRF have been noted along with larger peak powers at the rearfoot and lower peak powers at the knee in the FFS group. Vertical loading rates are also lower in FFS. RFS that have injuries thought to be associated with the force transient present with heel contact may do well to adopt a forefoot strike pattern resulting in the elimination of the impact peak and reduction of the loading rate. However, it is not known whether simply instructing someone to "run on their toes" results in a biomechanical profile characteristic of a practiced or natural FFS.”
Moving along...
“Improved strength going minimalist or barefoot? sorry, not according to the published literature “Effect of Minimalist Footwear on Medial Arch Height Justin F. Shroyer et al and Effect of Minimalist Footwear on Arch Rigidity Index Cory E. Etheredge et al. Hey .. check it out.. it out there in the public domain for all to see.. I am not making this up.. we deal with facts, not opinion, folklaw and myth.”
Fact – these once again are conference abstracts, not peer reviewed publications. What’s more, my suspicion is that arch height is more related to ligament laxity and joint congruence than it is to muscle strength, so I’m not sure these studies can even answer the question of whether muscle strength increased as a result of wearing minimalist shoes. Better would be to actually look at MRIs and consider cross-section area before and after the intervention. You know what, this has been done! If we’re in the business of citing abstracts, how about Potthast et al. 2005 who showed that training in the Nike Free compared to a traditional shoe increased cross sectional area of the flexor hallucis longus, and improved toe flexion strength, plantarflexor strength, and dorsiflexor strength.
Furthermore, arch height or arch collapse measured statically are not good indicators of what the arch does dynamically in a person who is actually running. See Dicharry et al., 2009 for more on this. Basically, you can have a hypermobile foot while standing, but still have the same amount of arch collapse as a person with a normal or hypomobile foot while walking or running, presumably due to adequate internal stability mechanisms (i.e., strong feet and legs).
Finally, there’s a snide remark about minimalist shoes following the path of toning shoes. However, I have a big problem with this. Toning shoes are an aberration that deviate humans farther from the condition we are born with (barefoot). Minimalist shoes bring us closer to our natural condition (barefoot). I would argue that the Asics Kinsei or Kayano has a lot more in common with a Sketchers Shape-Up than the Vibram Fivefingers do. I, for one, was not born with a hunk of unstable cushioning under my foot (like the Sketchers provide), nor was I born with my heel lifted 12mm off the ground with a support element wedged below my arch.
I’ll finish by playing Bartold’s game a bit. Visit the ASICS shoe fit guide. It states this:
“Pronation is a normal, natural rolling motion that helps to attenuate shock. Some runners find that their foot does not roll all the way in, making the foot work harder to push off properly. This is known as underpronation (or supination). Conversely, a foot that rolls inward too much in known as overpronation. Runners who underpronate (or, supinate) would feel more comfortable with a Cushioning shoe. Overpronators do better with Maximum Support, and those with a more neutral stride would do well with Structured Cushioning.”
How do you know which category you belong to? What you’ll find next are instructions on how to determine your arch type based on the “wet footprint test.” Once you determine your arch type, you can translate it into a pronation category and choose a shoe from one of three categories: high arch gets cushioning, medium arch gets structure cushioning, low arch gets maximum support. These are basically different words for neutral, stability, and motion control. Since we’re in the business of asking for peer reviewed, published evidence, I’d ask what the evidence for using arch height to choose a shoe might be? I’d ask whether pronation has been reliably shown as a major cause of running injury that needs to be controlled by a shoe? I’d ask whether ASICS shoes or pronation control devices have been proven to prevent injuries?
Surely the folks at ASICS must be aware of the paper by Ryan et al., 2010. They showed that neutral runners did better in stability shoes, overpronators did better in neutral shoes, and all severe overpronators in motion control shoes got hurt. In other words, either the shoes don’t do what they are supposed to, or static measures of the foot are not a good basis for assigning shoes. And the study was supported by Nike.
How about the series of studies by the military (Knapik et al., 2009; Knapik et al., 2010a; Knapik et al., 2010b) which showed that when assigning shoes based upon arch type, recruits (thousands of them were included in these studies) were just as well off being assigned a stability shoe by default as they were being put in the correct type of shoe for their arch type. So much for that wet test ASICS!
How about Dicharry et al., 2009 who showed that static measures of arch collapse do yield distinct groups, but that those distinctions disappear when walking and are tiny at best when running? How about Nigg et al., 1993 who found that “arch height does not influence either maximal eversion movement or maximal internal leg rotation during running stance.”
When criticizing minimalist advocates for lacking evidence, it seems that the lack of evidence is not so glaring as it is made to seem when you do dig into the literature. Without a doubt, there is some amount of contradiction, which is why this debate gets so heated these days. What’s more, some of the evidence that is out there casts serious doubt on the very process that ASICS recommends when it comes to choosing one of their shoes – what could be more fundamental to what a shoe company needs to do than accurately advise its customers on how to choose a shoe?
I think I’ve said enough here. My position is and has been that each runner is an individual, and I agree with Bartold when he states that. Given this, different runners have different preferences and needs. Some may want a 12mm lifted shoe, but others don’t. Some of those who don’t might have made the switch to escape a long term injury, and it’s clear that in many cases switching to minimalist shoes has helped. Some (like me) switch simply because we enjoy running in minimalist shoes more than in big heavy clunkers (and yes, I have run in Asicsa Kayanos as well as the 2100 series). I was never injured seriously in bulky shoes, and I haven’t been injured seriously in minimalist shoes. I may or may not be faster now, it’s really hard to tell. But I will say that I am enjoying running more, and that’s all that really matters to me, and I really don’t care if that gets published in a peer reviewed journal.
Let’s finish with another quite from Bartold, this time from a 2002 radio interview:
“I think unquestionably Zola Budd got it right when she was running barefoot. I think the signs from all the laboratories around the world would support that the human foot is probably the perfect model, but of course it’s impractical for most people wanting to go out running barefoot, there are too many obstacles, and of course you know, you might get injured by a sharp object, and the surfaces we run on transmit too much shock. But in a perfect environment on a perfect surface, then an unshod foot is probably the best way to go.”
Head over to Zero Drop if you want to see more on this discussion.
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