Switching to a Forefoot Strike: How Does it Affect Lower Back Movement and Shock Applied to the Body

A new study was just released ahead-of-print on the Medicine & Science in Sport & Exercise website. The study was authored by Traci Delgado of UNLV and colleagues, and is titled “Effects of Foot Strike on Low Back Posture, Shock Attenuation, and Comfort in Running.”

The goal of the study was to determine how heel striking vs. forefoot striking while running might alter: 1) lower back movement, 2) peak leg acceleration, 3) impact shock attenuation (i.e., how much shock is attenuated from the shin to the head), and 4) subjective comfort.

Methods

To address these questions, the researchers had 43 runners (24 male, 19 female) run barefoot on a treadmill using both a heel striking and a forefoot striking gait. Since 84% of the runners were heel strikers, in the vast majority of cases forefoot striking was a novel gait with which the runners had little or no experience. Shock was measured using accelerometers attached to the tibia and head, and lower back movement was measured using an electrogoniometer.

Results

Results of this study showed that running with a forefoot strike:
1) decreased total range of motion in the lower back, but did not alter peak   flexion or extension
2) reduced peak tibial acceleration
3) reduced shock attentuation from the shin to head (since there was less shock to attenuate)
4) reduced subject running comfort

Commentary

One of my critiques of this paper is the manner in which they cued a forefoot strike. Here’s what they told runners to do: “1) ‘try to run on your toes’ and 2) ‘do not let your heels touch the ground.’”

This is not the typical way barefoot runners run (the heel almost always comes down after forefoot contact – see the video below from the NYC Barefoot Run), and is the same cueing applied in a previous study, which I wrote about in an article for Lower Extremity Review:

“…Laughton et al. found no significant difference in loading rates between rearfoot and forefoot strikers and increased tibial acceleration in forefoot-striking runners. However, they looked at natural rearfoot strikers asked to switch to a forefoot strike pattern rather than natural forefoot-striking runners, and, furthermore, they instructed runners to run with a “toe-strike” and not let the heel touch the ground. In my observation, natural toe running without heel contact is extremely rare among runners, and the authors point out that running with this style of gait could have caused artificial stiffening of the leg, leading to an increase in tibial shock.”

Interestingly, even though they advised runners to run in a similar manner, Delgado et al. actually found that tibial acceleration was lower in forefoot strikers in this case. This is the opposite of what Laughton et al. found, and I’d be curious to see the results if the heel were allowed to come since that would allow increased use of the ankle and calf musculature in shock absorption and could further reduce the need for movement at places like the knee, hip, and lower back.

Regarding the finding that adopting a FFS reduced overall back movement, they report the following:

“Greater overall low back excursion with a RFS pattern may suggest that this pattern creates a greater demand for stability in the lumbar spine. Therefore, this foot strike could possibly not be beneficial for individuals with stability problems, including hypermobility or atrophied lumbar spine musculature. However, the change in ROM did not exceed known error of the measuring device for lumbar ROM, suggesting that the effect may not be clinically significant even though it reached statistical significance.”

Thus, the results thus could indicate a positive effect of switching to a forefoot strike for those with lower back pain, but the difference was not of such a magnitude that they felt comfortable stating this with certainty (anybody experienced a reduction in lower back pain as a result of changing footstrike? – let us know in the comments). Again, it would be interesting to see if things might change with slightly different cueing and greater experience with a forefoot strike – it’s always difficult to know with instantaneous changes with a novel movement pattern will change with time. Following on the the latter point, the authors propose that the reason for the perception that heel striking while barefoot was more comfortable despite causing greater shock was because the forefoot strike was novel for most of the subjects (I can’t help but wonder if the advice “to run on your toes” was also detrimental to comfort – this style of forefoot striking puts a lot more strain on the calf muscles).

Finally, regarding impact shock they say the following:

“This study revealed that there was lesser peak leg impact at contact when running with a FFS pattern. This is consistent with current evidence suggesting that running with a FFS would decrease shock when compared to running RFS (6,29,31). Shock attenuation was also observed to be greater with RFS than FFS; there is more shock absorbed throughout the body when running RFS. This may be due to the overall greater foot-ground impact to be generated in RFS, thus increasing the magnitude of shock to be attenuated.”

So, like many other studies, this one shows that running barefoot with a forefoot strike reduces shock to the body relative to running barefoot with a heel strike. Not much surprise there, but another piece of evidence suggesting that if you plan to run barefoot, it may be best to avoid those heels!

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New York Times on the “Myths” of Running: Is There a Best Way to Run

Gina Kolata of the New York Times wrote an article that appeared in the paper today. The title is “Myths of Running: Forefoot, Barefoot, and Otherwise,” and the article opens with the following question:

“Is there a best way to run, so that you use the least energy and go the fastest?”

Kolata goes on to report data from studies showing that elites at the Olympic Trials land in all kinds of different ways (true), and reports on studies that show no significant difference between foot strikes in terms of efficiency (also true). I’ve got no problem with any of this.

My main issues with the article are the following:

1. It’s fine to ask if there is a best way to run from an economy and speed standpoint, but I think that it also bears mentioning that the form that let’s you run fastest may not be the form that minimizes your injury risk.

Many of us like and want to run fast, but would prioritize our health over performance in a race. Plenty of runners could care less about racing, so economy and speed matter very little. Granted, she was very open in writing the article with a focus on economy and speed, but she also writes “Proponents say barefoot running is more natural — humans evolved to run without shoes — and economical.” Maybe some barefoot proponents claim this with regard to economy, but most of the barefoot runners I know started doing it simply because they hurt less when they take their shoes off.

2. The article was overly foot-centric. Foot strike is but one aspect of gait, and my guess is that if you looked at other aspects of form you’d see a lot more similarity among the elites when compared to more recreational runners (e.g., hip extension, limb position on landing, etc.). Part of the problem with the form debate over the past few years is that it has focused way too much on the foot, ignoring other, perhaps more important aspects of gait. I am just as guilty of this as anyone else, but it’s time to take the foot off it’s EVA cushioned throne and take a broader view of form.

3. Some statements are misleading. For example, she writes that “…studies have repeatedly shown that when people try to change their natural running style, they tend to use more energy to cover the same distance.” Well, that’s because most studies that look at things like this look at short or even instantaneous form changes. They take a runner, have them run in their normal form, then ask them to force some change and make a comparison. Any new motor pattern is going to take time to learn, and until it is learned I’d fully expect it to be less efficient!

Furthermore, ignoring speed/economy, multiple studies have shown that gait retraining can provide benefits in terms of reducing limb loading, reducing pain, and in some cases can resolve long-term injuries – it may not make you more efficient, but in some cases changing form is the only way people have be able to keep running. Any running at all is going to be faster than sitting on the couch.

Regarding Rodger Kram’s barefoot/shod study (which I wrote about here), Kolata says:

“In a study published this year, Dr. Kram and his students found that runners who wore very lightweight shoes were more efficient than those who ran barefoot. (The barefoot runners wore weights on their feet to mimic the weight of the shoes, so that this would not be a factor in the results.)”

The important point here is that the study actually showed that running fully barefoot was not significantly different in terms of economy from running in a lightweight shoe. It was only when weights equivalent to the weight of the shoe were added that “barefoot” became less economical.

Kram’s second study confirmed this again, finding that “metabolic power requirements for running barefoot and in lightweight running shoes were not significantly different” on a rigid treadmill surface. Adding 10mm of foam to the treadmill belt did significantly improve economy in barefoot runners, but increasing cushioning to 20mm did not. The point is that running barefoot on a moderately cushioned surface is more economical than running barefoot on a rigid surface, but running barefoot is equally economical compared to running in a lightweight shoe (it’s probably simply the case that there are differences in how the muscles divvy up the work in the two conditions). Based on these results, they state that “it appears that the positive effects of shoe cushioning counteract the negative effects of added mass, resulting in a metabolic cost for shod running approximately equal to that of barefoot running.” For some people it might be better, for others it might be worse, and the differences wash out in a non-significant difference between the two conditions.

So, to make a long story short, all of the studies that Kolata writes about basically say that there’s little difference between foot strikes and shod/barefoot when it comes to speed and economy. I guess the “myths” would then be that one foot strike or footwear condition is better than another. At an individual level this basically means “do what feels best to you and enjoy it!”

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New York Times on the “Myths” of Running: Is There a Best Way to Run

Gina Kolata of the New York Times wrote an article that appeared in the paper today. The title is “Myths of Running: Forefoot, Barefoot, and Otherwise,” and the article opens with the following question:

“Is there a best way to run, so that you use the least energy and go the fastest?”

Kolata goes on to report data from studies showing that elites at the Olympic Trials land in all kinds of different ways (true), and reports on studies that show no significant difference between foot strikes in terms of efficiency (also true). I’ve got no problem with any of this.

My main issues with the article are the following:

1. It’s fine to ask if there is a best way to run from an economy and speed standpoint, but I think that it also bears mentioning that the form that let’s you run fastest may not be the form that minimizes your injury risk.

Many of us like and want to run fast, but would prioritize our health over performance in a race. Plenty of runners could care less about racing, so economy and speed matter very little. Granted, she was very open in writing the article with a focus on economy and speed, but she also writes “Proponents say barefoot running is more natural — humans evolved to run without shoes — and economical.” Maybe some barefoot proponents claim this with regard to economy, but most of the barefoot runners I know started doing it simply because they hurt less when they take their shoes off.

2. The article was overly foot-centric. Foot strike is but one aspect of gait, and my guess is that if you looked at other aspects of form you’d see a lot more similarity among the elites when compared to more recreational runners (e.g., hip extension, limb position on landing, etc.). Part of the problem with the form debate over the past few years is that it has focused way too much on the foot, ignoring other, perhaps more important aspects of gait. I am just as guilty of this as anyone else, but it’s time to take the foot off it’s EVA cushioned throne and take a broader view of form.

3. Some statements are misleading. For example, she writes that “…studies have repeatedly shown that when people try to change their natural running style, they tend to use more energy to cover the same distance.” Well, that’s because most studies that look at things like this look at short or even instantaneous form changes. They take a runner, have them run in their normal form, then ask them to force some change and make a comparison. Any new motor pattern is going to take time to learn, and until it is learned I’d fully expect it to be less efficient!

Furthermore, ignoring speed/economy, multiple studies have shown that gait retraining can provide benefits in terms of reducing limb loading, reducing pain, and in some cases can resolve long-term injuries – it may not make you more efficient, but in some cases changing form is the only way people have be able to keep running. Any running at all is going to be faster than sitting on the couch.

Regarding Rodger Kram’s barefoot/shod study (which I wrote about here), Kolata says:

“In a study published this year, Dr. Kram and his students found that runners who wore very lightweight shoes were more efficient than those who ran barefoot. (The barefoot runners wore weights on their feet to mimic the weight of the shoes, so that this would not be a factor in the results.)”

The important point here is that the study actually showed that running fully barefoot was not significantly different in terms of economy from running in a lightweight shoe. It was only when weights equivalent to the weight of the shoe were added that “barefoot” became less economical.

Kram’s second study confirmed this again, finding that “metabolic power requirements for running barefoot and in lightweight running shoes were not significantly different” on a rigid treadmill surface. Adding 10mm of foam to the treadmill belt did significantly improve economy in barefoot runners, but increasing cushioning to 20mm did not. The point is that running barefoot on a moderately cushioned surface is more economical than running barefoot on a rigid surface, but running barefoot is equally economical compared to running in a lightweight shoe (it’s probably simply the case that there are differences in how the muscles divvy up the work in the two conditions). Based on these results, they state that “it appears that the positive effects of shoe cushioning counteract the negative effects of added mass, resulting in a metabolic cost for shod running approximately equal to that of barefoot running.” For some people it might be better, for others it might be worse, and the differences wash out in a non-significant difference between the two conditions.

So, to make a long story short, all of the studies that Kolata writes about basically say that there’s little difference between foot strikes and shod/barefoot when it comes to speed and economy. I guess the “myths” would then be that one foot strike or footwear condition is better than another. At an individual level this basically means “do what feels best to you and enjoy it!”

Read More

Merrell Bare Access 2: First Impressions and Giveaway

One of the things that I like about the Merrell Barefoot line is that they use the same last for all of the shoes in it. For example, today I spent the entire work day in a pair of brown leather Tough Gloves, and then finished the day with a 4 mile run in the new Bare Access 2. The fit of the two shoes is identical, so the transition was seamless.

The Bare Access 2 is the newest addition to the Merrell Barefoot line, and is the successor to a shoe that I like a lot and reviewed not too long ago. The Bare Access is Merrell’s cushioned, zero drop offering, and it was a strong enough performer that it made my list of recommended running shoes. In a niche that is growing rapidly, the original Bare Access scored points in having a nice, roomy toebox, a lightweight, reasonably flexible build, and a comfortable ride out on the road.

For the most part, most everything that I liked about the original Bare Access carries over into the new model. Fit is identical, cushioning is similarly firm (zero drop, 13-14mm stack height), and interior comfort is excellent (note: as with other shoes in the Merrell line, the BA2 has a contoured fit under the arch, so if you don’t like arch support, you may not like this shoe).

The main differences between the BA1 and BA2 include the following:

Merrell Bare Access 2 (top) and 1 (bottom)

1. The Bare Access 2 has a redesigned upper. I was initially concerned when I saw the upper of the BA2 since it looks and feels like the monofilament style upper that has suffered tearing issues in so many shoes of late. Merrell themselves had trouble with the upper of the original Mix Master trail shoe and had to pull it from the market. I emailed my contacts at Merrell about this and received the following response:

“The Bare Access 2 mesh is polyester.....not monomesh nylon. The polyester mesh has passed all of our stringent testing. We have had no issues on the extended wear testing as well. From a distance, the mesh has the sheer look, but their makeups are totally different. Both from a composition stand point and also from a weave structure.”

Given Merrell’s reputation for quality build, I suspected they wouldn’t make the same mistake twice, and this response allays my fears about upper durability in the BA2. I like the look of the BA2 moreso than the BA1, so I guess that’s a score in favor of the new model. In looking at the photo below, it appears that the space between the lace rows is much wider in the new Bare Access – not sure if this means anything, but it’s clearly a design difference and may allow for a better fit for those with a high-volume midfoot.

Merrell Bare Access 2 (top) and 1 (bottom)

2. The second major difference is that the BA2 has a full coverage Vibram rubber outsole compared to the mostly exposed foam sole of the BA1. One complaint I have frequently seen about the sole of the original Bare Access is that abrasion tends to eat away at the surface of the exposed foam (you can see this in the photo below). This happened in my shoes too, but it was more just cosmetic scuffing than any real breakdown of the sole material.

The Vibram sole of the BA2 should improve durability in the newer model, but the expense is that it adds about an ounce to the weight of the shoe (the BA2 comes in at right around 7 ounces in size 10 compared to 6.2 ounces for the BA1). It also makes for a bit more ground contact noise on the run since the rubber has less give than exposed foam. Merrell could probably remove a good bit of the rubber from the midfoot region of the shoe without sacrificing durability to shed some weight and improve flexibility (the horizontal white grooves across the forefoot do allow for pretty good flex up front). One point to note is that the grooves in the rubber outsole tend to pick up small pebbles – I don’t notice this while running since they are tiny.

Merrell Bare Access 2 (top) and 1 (bottom). Not the abrasion of the red sole on the BA1 below the toes. You can also see how the rubber sole of the BA2 picks up little pebbles.

That pretty much sums up the major differences between the two shoes, and will refer you back to my Bare Access 1 review for more details. I’ve run in the BA2 three times so far, and the experience has been great. It’s a bit firmer than I typically like, but that’s just a personal preference, and it does make for a stable feel underfoot. Unlike some, I enjoy the glove-like fit provided by the contoured arch, and the Merrell Barefoot last works really well on my feet – nearly perfectly proportioned.

Comparing it to other shoes in the cushioned, zero drop niche, the Bare Access 2 is lighter and more flexible than the Altra Instinct 1.5, but firmer and not nearly as flexible as the Skechers GoBionic. I’d compare it most closely to the New Balance Minimus Road MR00, but the BA2 is a bit wider through the midfoot, which is a plus for me. All of these are excellent shoes, so the choice largely comes down to one of personal taste with regard to fit, flexibility, and firmness underfoot.

For more information and to purchase the shoes, visit the Merrell webpage to view the men’s and women’s versions of the Bare Access 2.

The original men's Bare Access can be purchased at a discounted price from Zappos.

For another take on the Bare Access 2, visit Believe in the Run, Biker Nate, Coach Caleb, and Vagabond Running.

---

Merrell Bare Access 2 Giveaway!

Use the Rafflecopter widget below to enter a giveaway to win one of two pairs of Merrell Bare Access 2 shoes – this is my first attempt to use this service, we’ll see how it goes!

a Rafflecopter giveaway

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Merrell Bare Access 2: First Impressions and Giveaway

One of the things that I like about the Merrell Barefoot line is that they use the same last for all of the shoes in it. For example, today I spent the entire work day in a pair of brown leather Tough Gloves, and then finished the day with a 4 mile run in the new Bare Access 2. The fit of the two shoes is identical, so the transition was seamless.

The Bare Access 2 is the newest addition to the Merrell Barefoot line, and is the successor to a shoe that I like a lot and reviewed not too long ago. The Bare Access is Merrell’s cushioned, zero drop offering, and it was a strong enough performer that it made my list of recommended running shoes. In a niche that is growing rapidly, the original Bare Access scored points in having a nice, roomy toebox, a lightweight, reasonably flexible build, and a comfortable ride out on the road.

For the most part, most everything that I liked about the original Bare Access carries over into the new model. Fit is identical, cushioning is similarly firm (zero drop, 13-14mm stack height), and interior comfort is excellent (note: as with other shoes in the Merrell line, the BA2 has a contoured fit under the arch, so if you don’t like arch support, you may not like this shoe).

The main differences between the BA1 and BA2 include the following:

Merrell Bare Access 2 (top) and 1 (bottom)

1. The Bare Access 2 has a redesigned upper. I was initially concerned when I saw the upper of the BA2 since it looks and feels like the monofilament style upper that has suffered tearing issues in so many shoes of late. Merrell themselves had trouble with the upper of the original Mix Master trail shoe and had to pull it from the market. I emailed my contacts at Merrell about this and received the following response:

“The Bare Access 2 mesh is polyester.....not monomesh nylon. The polyester mesh has passed all of our stringent testing. We have had no issues on the extended wear testing as well. From a distance, the mesh has the sheer look, but their makeups are totally different. Both from a composition stand point and also from a weave structure.”

Given Merrell’s reputation for quality build, I suspected they wouldn’t make the same mistake twice, and this response allays my fears about upper durability in the BA2. I like the look of the BA2 moreso than the BA1, so I guess that’s a score in favor of the new model. In looking at the photo below, it appears that the space between the lace rows is much wider in the new Bare Access – not sure if this means anything, but it’s clearly a design difference and may allow for a better fit for those with a high-volume midfoot.

Merrell Bare Access 2 (top) and 1 (bottom)

2. The second major difference is that the BA2 has a full coverage Vibram rubber outsole compared to the mostly exposed foam sole of the BA1. One complaint I have frequently seen about the sole of the original Bare Access is that abrasion tends to eat away at the surface of the exposed foam (you can see this in the photo below). This happened in my shoes too, but it was more just cosmetic scuffing than any real breakdown of the sole material.

The Vibram sole of the BA2 should improve durability in the newer model, but the expense is that it adds about an ounce to the weight of the shoe (the BA2 comes in at right around 7 ounces in size 10 compared to 6.2 ounces for the BA1). It also makes for a bit more ground contact noise on the run since the rubber has less give than exposed foam. Merrell could probably remove a good bit of the rubber from the midfoot region of the shoe without sacrificing durability to shed some weight and improve flexibility (the horizontal white grooves across the forefoot do allow for pretty good flex up front). One point to note is that the grooves in the rubber outsole tend to pick up small pebbles – I don’t notice this while running since they are tiny.

Merrell Bare Access 2 (top) and 1 (bottom). Not the abrasion of the red sole on the BA1 below the toes. You can also see how the rubber sole of the BA2 picks up little pebbles.

That pretty much sums up the major differences between the two shoes, and will refer you back to my Bare Access 1 review for more details. I’ve run in the BA2 three times so far, and the experience has been great. It’s a bit firmer than I typically like, but that’s just a personal preference, and it does make for a stable feel underfoot. Unlike some, I enjoy the glove-like fit provided by the contoured arch, and the Merrell Barefoot last works really well on my feet – nearly perfectly proportioned.

Comparing it to other shoes in the cushioned, zero drop niche, the Bare Access 2 is lighter and more flexible than the Altra Instinct 1.5, but firmer and not nearly as flexible as the Skechers GoBionic. I’d compare it most closely to the New Balance Minimus Road MR00, but the BA2 is a bit wider through the midfoot, which is a plus for me. All of these are excellent shoes, so the choice largely comes down to one of personal taste with regard to fit, flexibility, and firmness underfoot.

For more information and to purchase the shoes, visit the Merrell webpage to view the men’s and women’s versions of the Bare Access 2.

The original men's Bare Access can be purchased at a discounted price from Zappos.

For another take on the Bare Access 2, visit Believe in the Run, Biker Nate, Coach Caleb, and Vagabond Running.

---

Merrell Bare Access 2 Giveaway!

Use the Rafflecopter widget below to enter a giveaway to win one of two pairs of Merrell Bare Access 2 shoes – this is my first attempt to use this service, we’ll see how it goes!

a Rafflecopter giveaway

Read More

Neutral Running Shoes Need Not Be the Goal for All Runners: More on Pronation Control

Over the past few years I’ve written several posts on problems with the pronation control/arch height model of fitting running shoes. These include the fact that runners generally have poor knowledge of how much they pronate, that static arch height does not correlate well with dynamic arch height, and that studies have shown little benefit in terms of injury reduction when shoes are assigned based on arch height or pronation control.

Several commenters on these posts have indicated that maybe it’s time to move away from stability shoes and give neutral shoes a try. I thought I’d share a few thoughts on this as I don’t necessarily think this is the way to approach things when it comes to running footwear.

Do Pronation-Control Categories Mean Anything?

One of the biggest problems with making neutral a goal is that it assumes that “stability” and “neutral” are actual categories with well defined limits and precise meaning. I don’t believe this to be the case. As far as I’m aware, and correct me if I’m wrong, there are not hard criteria a shoe must meet in order to be classified as a stability or a neutral shoe. It seems that a medial post or some other type of pronation control “technology” is all that’s needed to make a shoe fall into the stability category.

Having run in a lot of shoes over the past few years (I’ve lost count, but wouldn’t be surprised if it’s over 75 now), I’ve rarely found the stability/neutral categorizations to be very helpful - I run in both with little issue. In fact, I’ve run recently in both the Saucony Guide 5 (stability) and Ride 5 (neutral) and I’ll be darned if I could tell you which is which if I put them on with my eyes closed. I’ve even run in neutral shoes with firm soles that almost feel too stable (e.g., many adidas shoes such as the adios 2 and Feather 2).

I think the reality is that there’s way more to making a shoe “stable” than just throwing a medial post on it (and it’s even debatable how effective posts are – gait expert and PT Jay Dicharry once told me that it’s one of the least effective methods of improving shoe stability since the foot pronates most after the post has left the ground during stance). If we define stability as a shoe that minimizes inward roll of the foot (what we runners colloquially refer to as pronation), I personally find that stability is mainly a function of cushioning firmness (firmer = more stable), cushioning amount (thinner sole = more stable), and shoe width (narrow shoes make me feel less stable). I also find torsional (twisting) flexibility to be important – stiff shoes with thick soles feel very slappy to me and I suspect they increase pronation velocity.

Another problem with making “neutral” a goal to strive for is that I don’t really know what neutral as a category means (or that neutral has any meaning for the foot either – read this post by Ian Griffiths for more on this). Some neutral shoes are so soft that they cave medially and cause the foot to pronate way more than it ever would when barefoot (like my wife’s foot in the Nike Free 5.0 at the top of this page; see also this post which hones in on this aspect of neutral shoes). Some are so firm that they feel more stable than a lot of “stability” shoes. The New Balance MT110 is a neutral trail shoe, but because the sole in my pair is so slanted from lateral to medial I can feel it forcing my foot to evert just standing in them – they gave me a case of posterior tibial tendinitis after a long trail run.

Look at the photos below for an example of how three “neutral” shoes can behave differently on the same person – this demonstrates well the lack of a standard response within a category:

adidas adizero Adios 1 (right) with high and narrow sole rolls over medially. Nike Lunar Racer (middle) with wide sole is more stable, and Asics Piranha (left) with lower profile has less tendency to tilt.

Here’s the same person showing foot movement barefoot and in stability and neutral shoes – the neutral shoe appears to cause a lot more inward roll than when he is barefoot:

Does Shoe Motion Correlate With Foot Motion?

An entirely separate issue is the fact that how a shoe moves may have little correlation with how the foot moves inside the shoe. For example, here is the Abstract of a classic 2000 paper by Alex Stacoff that tried to differentiate shoe movement from the actual movement of the foot inside the shoe by inserting pins into the foot and leg bones:

Abstract

Barefoot running kinematics has been described to vary considerably from shod running. However, previous investigations were typically based on externally mounted shoe and/or skin markers, which have been shown to overestimate skeletal movements. Thus, the purpose of this study was to compare calcaneal and tibial movements of barefoot versus shod running using skeletal markers. Intracortical bone pins with reflective marker triads were inserted under standard local anesthetic into the calcaneus and tibia of five healthy male subjects. The subjects ran barefoot, with a normal shoe, with three shoe soles and two orthotic modifications. The three-dimensional tibiocalcaneal rotations were determined using a joint coordinate system approach. Test variables were defined for eversion and tibial rotation. The results showed that the differences in bone movements between barefoot and shod running were small and unsystematic (mean effects being less than 2°) compared with the differences between the subjects (up to 10°). However, differences may occur during midstance when extreme shoe modifications (i.e. posterior orthosis) are used. It is concluded that calcaneal and tibial movement patterns do not differ substantially between barefoot and shod running, and that the effects of these interventions are subject specific. The result of this in vivo study contrasts with previous investigations using skin and shoe mounted markers and suggests that these discrepancies may be the result of the overestimation with externally mounted markers.

The point made by this study is that the movement we see when looking at the shoe from behind may not actually reveal much about how the foot inside the shoe is moving. In other words, a stability shoe may look like it keeps the foot in a more “neutral” position, but the foot may simply be pronating inside the shoe just as much as it would when barefoot.

The Origin of Pronation Control

Another thing to consider is why pronation control devices in shoes were developed in the first place – was the original goal to correct a problem with our feet? I’m not so sure…

The footwear trend in the 1970’s was to add additional cushioning to shoes, particularly under the heel. The reason for this was that Achilles tendon problems were among the most commonly reported injuries in the early 70’s, and lifting the heel was thought to reduce strain on the Achilles. I have also heard that adding cushion was also done to accommodate a changing demographic of runners (new to the sport, perhaps not as fit) – read this book excerpt for more on running injuries/shoes in the 1970’s. However, adding cushion seemed to have some side effects. The late 1970’s saw a decrease in Achilles problems, but a dramatic increase in knee injuries. The latter were thought to be linked to reduced rearfoot control due to the cushioning added to shoes. Excessive rearfoot movement was linked to excessive internal tibial rotation (i.e., the shin twisting inward), which was in turn thought to contribute to the development of problems at the knee. This gave rise to the addition of pronation control elements in an effort to control the rearfoot and save the knee (knee injuries are still by far the most common running injury).

Benno Nigg, one of the scientists who was heavily involved with the study of shoes during this time period (and is still  a major researcher in the shoe world today) has since stated that attempting to control foot motion was a mistake – here’s a snippet from a 2010 Runner’s World article featuring Nigg:

“…In the early 1980s, Nigg was working as a consultant for Nike on its line of tennis shoes. While there, he offered input on the need to add more structure to Air models because the much-lauded Air units created even more instability than traditional foam. "I pushed the cushioning trend as much as anyone," the broad-shouldered Nigg says in his Swiss accent. "And I take the blame for pronation devices as well."”

So the reality is that pronation control technology seems to have appeared to correct problems caused by the addition of cushion and heel lifts to shoes. It was a new element added to shoes to correct for problems created by another new element. (If you are interested in footwear history from the 1970’s, I highly recommend that you read The Running Shoe Book from 1980 by Peter Cavanagh).

In fact, I don’t get the feeling that the appearance of pronation control had anything to do with correcting an inherent problem with our feet (it was correcting a problem with our shoes!). Unfortunately, it has morphed into that for many runners today who feel that they “need” stability because they are an “overpronator” – in this sense overpronation has come to be treated almost as a pathological condition that needs correction lest you want to endure certain pain and suffering.

How Do You Find the Right Shoe?

What can we make of all of this, and how should runners find the right shoe?

I prefer to think of shoes in much the same way I look at runners – each is an individual with its own properties. I’m not at all a fan of footwear categories because there is no defining set of criteria that can be applied to each category, and no standardization as to just how stable a given shoe is. In a similar manner, I don’t like using “minimalist” to define a specific category as there is such a huge amount of variation in what different people would put into it. Is the Saucony Kinvara minimalist? How about the Altra Instinct? Thus, I don’t find the categories “stability” and “neutral” to be all that informative and basically just ignore them now when choosing shoes for myself.

My general feeling is that unless an individual runner has a specific pathology that has been linked to increased injury risk, they should aim to find a shoe that allows their feet to move as they want to move. Don’t attempt to control foot movement, and don’t wear something that is going to cause the foot to move even more than it would on its own. I do think video analysis can help with this to a degree, but keep in mind that we typically only see how much the shoe moves – it’s much harder to discern how much the foot is moving inside the shoe.

Don’t focus too much on categories, focus more on how individual shoes feel – comfort is good, and specifically comfort while running in a shoe, not while standing in it in a store. Benno Nigg, the scientist mentioned above, stated in an article by Amby Burfoot that “Comfort is not easy to define, but it's ‘probably the most important variable’ for sport-shoe selection.” I would agree with him – I can usually tell after a single run whether a shoe is going to work for me, and it mainly has to do with knowing how a lot of different shoes feel on my feet. A shoe that feels comfortable on the very first run is generally one that stays in my rotation for the long term. I would also agree that comfort is hard to define, but for me I think it’s mainly just how good a shoe is at letting my body do its thing without getting in the way – a comfortable shoe is one that I barely even notice when I run.

The challenge is helping runners who aren’t shoe reviewers with access to large numbers of shoes figure out their own comfort zone – my feeling is that’s where the human factor comes in. Rely on your shoe-geek friends, knowledgeable and open minded specialty store clerks, and others with extensive shoe and running experience to help you out. One day I hope science will have better answers for us on how best to fit shoes, but I don’t think we’re there yet, and until then it remains more an art and a personal journey. It’s a journey that need not have neutral as its end goal.

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Neutral Running Shoes Need Not Be the Goal for All Runners: More on Pronation Control

Over the past few years I’ve written several posts on problems with the pronation control/arch height model of fitting running shoes. These include the fact that runners generally have poor knowledge of how much they pronate, that static arch height does not correlate well with dynamic arch height, and that studies have shown little benefit in terms of injury reduction when shoes are assigned based on arch height or pronation control.

Several commenters on these posts have indicated that maybe it’s time to move away from stability shoes and give neutral shoes a try. I thought I’d share a few thoughts on this as I don’t necessarily think this is the way to approach things when it comes to running footwear.

Do Pronation-Control Categories Mean Anything?

One of the biggest problems with making neutral a goal is that it assumes that “stability” and “neutral” are actual categories with well defined limits and precise meaning. I don’t believe this to be the case. As far as I’m aware, and correct me if I’m wrong, there are not hard criteria a shoe must meet in order to be classified as a stability or a neutral shoe. It seems that a medial post or some other type of pronation control “technology” is all that’s needed to make a shoe fall into the stability category.

Having run in a lot of shoes over the past few years (I’ve lost count, but wouldn’t be surprised if it’s over 75 now), I’ve rarely found the stability/neutral categorizations to be very helpful - I run in both with little issue. In fact, I’ve run recently in both the Saucony Guide 5 (stability) and Ride 5 (neutral) and I’ll be darned if I could tell you which is which if I put them on with my eyes closed. I’ve even run in neutral shoes with firm soles that almost feel too stable (e.g., many adidas shoes such as the adios 2 and Feather 2).

I think the reality is that there’s way more to making a shoe “stable” than just throwing a medial post on it (and it’s even debatable how effective posts are – gait expert and PT Jay Dicharry once told me that it’s one of the least effective methods of improving shoe stability since the foot pronates most after the post has left the ground during stance). If we define stability as a shoe that minimizes inward roll of the foot (what we runners colloquially refer to as pronation), I personally find that stability is mainly a function of cushioning firmness (firmer = more stable), cushioning amount (thinner sole = more stable), and shoe width (narrow shoes make me feel less stable). I also find torsional (twisting) flexibility to be important – stiff shoes with thick soles feel very slappy to me and I suspect they increase pronation velocity.

Another problem with making “neutral” a goal to strive for is that I don’t really know what neutral as a category means (or that neutral has any meaning for the foot either – read this post by Ian Griffiths for more on this). Some neutral shoes are so soft that they cave medially and cause the foot to pronate way more than it ever would when barefoot (like my wife’s foot in the Nike Free 5.0 at the top of this page; see also this post which hones in on this aspect of neutral shoes). Some are so firm that they feel more stable than a lot of “stability” shoes. The New Balance MT110 is a neutral trail shoe, but because the sole in my pair is so slanted from lateral to medial I can feel it forcing my foot to evert just standing in them – they gave me a case of posterior tibial tendinitis after a long trail run.

Look at the photos below for an example of how three “neutral” shoes can behave differently on the same person – this demonstrates well the lack of a standard response within a category:

adidas adizero Adios 1 (right) with high and narrow sole rolls over medially. Nike Lunar Racer (middle) with wide sole is more stable, and Asics Piranha (left) with lower profile has less tendency to tilt.

Here’s the same person showing foot movement barefoot and in stability and neutral shoes – the neutral shoe appears to cause a lot more inward roll than when he is barefoot:

Does Shoe Motion Correlate With Foot Motion?

An entirely separate issue is the fact that how a shoe moves may have little correlation with how the foot moves inside the shoe. For example, here is the Abstract of a classic 2000 paper by Alex Stacoff that tried to differentiate shoe movement from the actual movement of the foot inside the shoe by inserting pins into the foot and leg bones:

Abstract

Barefoot running kinematics has been described to vary considerably from shod running. However, previous investigations were typically based on externally mounted shoe and/or skin markers, which have been shown to overestimate skeletal movements. Thus, the purpose of this study was to compare calcaneal and tibial movements of barefoot versus shod running using skeletal markers. Intracortical bone pins with reflective marker triads were inserted under standard local anesthetic into the calcaneus and tibia of five healthy male subjects. The subjects ran barefoot, with a normal shoe, with three shoe soles and two orthotic modifications. The three-dimensional tibiocalcaneal rotations were determined using a joint coordinate system approach. Test variables were defined for eversion and tibial rotation. The results showed that the differences in bone movements between barefoot and shod running were small and unsystematic (mean effects being less than 2°) compared with the differences between the subjects (up to 10°). However, differences may occur during midstance when extreme shoe modifications (i.e. posterior orthosis) are used. It is concluded that calcaneal and tibial movement patterns do not differ substantially between barefoot and shod running, and that the effects of these interventions are subject specific. The result of this in vivo study contrasts with previous investigations using skin and shoe mounted markers and suggests that these discrepancies may be the result of the overestimation with externally mounted markers.

The point made by this study is that the movement we see when looking at the shoe from behind may not actually reveal much about how the foot inside the shoe is moving. In other words, a stability shoe may look like it keeps the foot in a more “neutral” position, but the foot may simply be pronating inside the shoe just as much as it would when barefoot.

The Origin of Pronation Control

Another thing to consider is why pronation control devices in shoes were developed in the first place – was the original goal to correct a problem with our feet? I’m not so sure…

The footwear trend in the 1970’s was to add additional cushioning to shoes, particularly under the heel. The reason for this was that Achilles tendon problems were among the most commonly reported injuries in the early 70’s, and lifting the heel was thought to reduce strain on the Achilles. I have also heard that adding cushion was also done to accommodate a changing demographic of runners (new to the sport, perhaps not as fit) – read this book excerpt for more on running injuries/shoes in the 1970’s. However, adding cushion seemed to have some side effects. The late 1970’s saw a decrease in Achilles problems, but a dramatic increase in knee injuries. The latter were thought to be linked to reduced rearfoot control due to the cushioning added to shoes. Excessive rearfoot movement was linked to excessive internal tibial rotation (i.e., the shin twisting inward), which was in turn thought to contribute to the development of problems at the knee. This gave rise to the addition of pronation control elements in an effort to control the rearfoot and save the knee (knee injuries are still by far the most common running injury).

Benno Nigg, one of the scientists who was heavily involved with the study of shoes during this time period (and is still  a major researcher in the shoe world today) has since stated that attempting to control foot motion was a mistake – here’s a snippet from a 2010 Runner’s World article featuring Nigg:

“…In the early 1980s, Nigg was working as a consultant for Nike on its line of tennis shoes. While there, he offered input on the need to add more structure to Air models because the much-lauded Air units created even more instability than traditional foam. "I pushed the cushioning trend as much as anyone," the broad-shouldered Nigg says in his Swiss accent. "And I take the blame for pronation devices as well."”

So the reality is that pronation control technology seems to have appeared to correct problems caused by the addition of cushion and heel lifts to shoes. It was a new element added to shoes to correct for problems created by another new element. (If you are interested in footwear history from the 1970’s, I highly recommend that you read The Running Shoe Book from 1980 by Peter Cavanagh).

In fact, I don’t get the feeling that the appearance of pronation control had anything to do with correcting an inherent problem with our feet (it was correcting a problem with our shoes!). Unfortunately, it has morphed into that for many runners today who feel that they “need” stability because they are an “overpronator” – in this sense overpronation has come to be treated almost as a pathological condition that needs correction lest you want to endure certain pain and suffering.

How Do You Find the Right Shoe?

What can we make of all of this, and how should runners find the right shoe?

I prefer to think of shoes in much the same way I look at runners – each is an individual with its own properties. I’m not at all a fan of footwear categories because there is no defining set of criteria that can be applied to each category, and no standardization as to just how stable a given shoe is. In a similar manner, I don’t like using “minimalist” to define a specific category as there is such a huge amount of variation in what different people would put into it. Is the Saucony Kinvara minimalist? How about the Altra Instinct? Thus, I don’t find the categories “stability” and “neutral” to be all that informative and basically just ignore them now when choosing shoes for myself.

My general feeling is that unless an individual runner has a specific pathology that has been linked to increased injury risk, they should aim to find a shoe that allows their feet to move as they want to move. Don’t attempt to control foot movement, and don’t wear something that is going to cause the foot to move even more than it would on its own. I do think video analysis can help with this to a degree, but keep in mind that we typically only see how much the shoe moves – it’s much harder to discern how much the foot is moving inside the shoe.

Don’t focus too much on categories, focus more on how individual shoes feel – comfort is good, and specifically comfort while running in a shoe, not while standing in it in a store. Benno Nigg, the scientist mentioned above, stated in an article by Amby Burfoot that “Comfort is not easy to define, but it's ‘probably the most important variable’ for sport-shoe selection.” I would agree with him – I can usually tell after a single run whether a shoe is going to work for me, and it mainly has to do with knowing how a lot of different shoes feel on my feet. A shoe that feels comfortable on the very first run is generally one that stays in my rotation for the long term. I would also agree that comfort is hard to define, but for me I think it’s mainly just how good a shoe is at letting my body do its thing without getting in the way – a comfortable shoe is one that I barely even notice when I run.

The challenge is helping runners who aren’t shoe reviewers with access to large numbers of shoes figure out their own comfort zone – my feeling is that’s where the human factor comes in. Rely on your shoe-geek friends, knowledgeable and open minded specialty store clerks, and others with extensive shoe and running experience to help you out. One day I hope science will have better answers for us on how best to fit shoes, but I don’t think we’re there yet, and until then it remains more an art and a personal journey. It’s a journey that need not have neutral as its end goal.

Read More

Minimalist Running Results in Fewer Injuries?: Survey Suggests that Traditionally Shod Runners are 3.41 Times More Likely to Get Hurt

Last week a flurry of articles appeared linking to the abstract of a new survey based study that suggested that traditionally shod runners are 3.41 times more likely to suffer a running-related injury than minimally shod runners. I opted to hold off on posting anything about the study until I had a chance to read the full text, which I have now done.

The study, titled “Relationships Among Self-reported Shoe Type, Footstrike Pattern, and Injury Incidence,” was authored by LTC Donald Goss of the US Army/Baylor University Doctoral Program in Physical Therapy and Dr. Michael Gross of the University of North Carolina. It will be published in the Oct/Dec issue of the Army Medical Department Journal.

Methods

The study authors crafted an internet survey and obtained responses from 2157 individual runners from Sept. 2010 to Dec. 2011. Of these, 1363 reported changing either their shoe type preference (traditional or minimalist) or foot strike in the previous year. Thus, the respondent pool was spit into two samples – 904 runners who completed the entire survey (not all did) and had not changed either shoe type or foot strike type in the previous year, and the 1363 who had made a switch in the previous year.

The specific survey question pertaining to injuries was the following:

“If an injury is defined as something that caused you to modify your training schedule for at least 1 week due to pain or discomfort (with or without formal medical care), have you experienced any lower extremity injuries in the past 12 months that you believe were caused by running?”

They followed this by asking respondents to specify the anatomical location of the injury (e.g., foot, ankle, knee, hip, etc.)

Results

Among the 904 respondents who had not switched shoe type or foot strike, 73% wore traditional running shoes, 25% wore minimal shoes (mean duration of minimalist shoe wear = 26 months), and the small remainder were primarily barefoot runners (only 16 total). Runners in the various groups were similar in mean height, age, and body mass, though minimalists were more likely to be male, had more years of running experience, and tended to report greater weekly mileage and faster training paces.

In terms of foot strike, 31% of the entire sample claimed to be heel strikers, 43% claimed to be midfoot strikers, 20% claimed to be forefoot strikers, and 6% were uncertain of their foot strike type. Barefoot and minimalist runners were more likely to self-report a midfoot or forefoot strike. The breakdown of self reported foot strike types among footwear groups looks like this:

	Foot Strike Type
Shoe Type	Heel	Midfoot	Forefoot
Traditional	41.4%	45.9%	12.7%
Minimalist	5.9%	48.5%	45.6%
Barefoot	0.0%	60.0%	40.0%

Regarding injuries, runners in traditional shoes were 3.41 times more likely to report an injury than experienced minimalist runners (46.7% vs. 13.7%). As seen in the figure below from the Army Medical Department Journal, injury percentages were higher among traditionally shod runners at every anatomical location surveyed.

Comparing injury rates among foot strike groups, rearfoot strikers reported an injury incidence of 52.4%. In contrast, 34.7% of midfoot strikers reported an injury, and 22.8% of forefoot strikers reported an injury.

As mentioned above, a large proportion of the initial survey sample was excluded from the above analyses because they had either switched foot strike (n = 866) or shoe type (848) in the previous year. The vast majority of these people claimed to have moved from heel striking in traditional shoes to midfoot or forefoot striking in minimal shoes. The main reason reported for switching was a desire to overcome an injury (40-50%). The group of 397 runners who reported changing footstrike due to injury collectively reported 500 injuries, and the 372 runners who reported changing footwear due to injury collectively reported 411 injuries. It’s not specified if these injuries include those both before and after the change, so it’s difficult to conclude whether they might all be termed “transition injuries.”

Commentary

This is an interesting study for a number of reasons, but I want to state clearly at the outset that it is based on self-reported survey responses, and as such should not be confused with a prospective experimental study. In other words, we must rely on the accuracy and honesty of the survey respondents, which opens up a lot of room for debate on the value of the findings.

Regarding this, I’ll say that I am very skeptical of the self-reported foot strike percentages. To their credit, the authors openly state this as well, and have themselves conducted a pilot study showing that only about 75% of runners accurately self-report their foot strike type, and that those claiming to be midfoot or forefoot strikers are more likely to be incorrect (i.e., at least one-third who claim to land on the midfoot or forefoot are actually heel strikers).

My own research has shown that in a large sample of traditionally shod marathon runners, approximately 90% are heel strikers. A similar percentage of heel strikers was found again in a recent analysis of foot strike patterns at the Milwaukee Lakefront marathon. Thus, the self reported heel striking frequency of 41.4% for traditionally shod runners is probably a dramatic underestimate. I also have reason to suspect that the 5.9% frequency of heel striking reported by minimalist runners is also a vast underestimate (I need to publish my data on this!). Given this, my feeling is that the high likelihood of significant self-reporting error makes the comparison of injury rates by foot strike of questionable value. The authors are very clear in pointing this out themselves, and indicate that confirmation of foot strike types would make for a more compelling analysis.

In contrast to foot strike type, one would hope that experienced runners responding to a survey like this would know what kind of shoe they put on their feet. The authors did a pilot on this as well and found that 98% of runners could correctly classify their shoe as “traditional” or “minimalist,” though the detailed criteria that they used to differentiate these categories are not provided. Given the likely higher accuracy of shoe type classification, the finding that traditionally shod runners reported 3.41 times as many injuries as experienced (> 1 year) minimalist runners is interesting. One would hope that the respondents accurately reported their injuries, and most runners should be able to recall injuries that caused them to alter their training for more than a week, but it is possible that this result is tainted by enthusiastic minimalists underreporting their injuries (the authors point this out as well). This is the reason why prospective and carefully controlled and monitored studies provide more reliable results than surveys – it minimizes bias.

If we assume that the self-reports are accurate, then this study suggests that those adapted to minimalist shoes are on average at a reduced risk of injury compared to traditionally shod runners. Lots of questions, but that’s the major conclusion. However, if you consider the fact that those who transitioned their footwear or foot strike within a year of completing the survey reported an awful lot of injuries (keeping in mind that it’s not clear whether these occurred before or after the transition), the results don’t necessarily mean that minimalist is better for all. It just means that those who make it through the transition period tend to do pretty well. It could also be a reflection of some other factor – perhaps experienced minimalists get to that point because they have inherently better form or are more injury resistant and would do fine in any kind of shoe. All we can do is speculate based on the survey reports.

Transition of any type changes stress to the body, so it’s not surprising to me that injuries are more common in this period (though another study suggested that barefoot running transition injuries are actually uncommon). The big question to me is what happens to those people who get injured in transition? It would be interesting to do a follow up and see how many of those injured during transition stuck with it, and what their longer term outcomes were like. In other words, is going minimalist and/or moving to a forefoot strike a short term risk for a long term gain? I’d also love to see a before/after analysis of form and foot strike type. Though this study raises provides some interesting results, as with any scientific paper it also raises a lot of questions. My hope is that answers to these questions will continue to appear in the coming years.

What do you think, do you believe the results of this study?

Read More

Minimalist Running Results in Fewer Injuries?: Survey Suggests that Traditionally Shod Runners are 3.41 Times More Likely to Get Hurt

Last week a flurry of articles appeared linking to the abstract of a new survey based study that suggested that traditionally shod runners are 3.41 times more likely to suffer a running-related injury than minimally shod runners. I opted to hold off on posting anything about the study until I had a chance to read the full text, which I have now done.

The study, titled “Relationships Among Self-reported Shoe Type, Footstrike Pattern, and Injury Incidence,” was authored by LTC Donald Goss of the US Army/Baylor University Doctoral Program in Physical Therapy and Dr. Michael Gross of the University of North Carolina. It will be published in the Oct/Dec issue of the Army Medical Department Journal.

Methods

The study authors crafted an internet survey and obtained responses from 2157 individual runners from Sept. 2010 to Dec. 2011. Of these, 1363 reported changing either their shoe type preference (traditional or minimalist) or foot strike in the previous year. Thus, the respondent pool was spit into two samples – 904 runners who completed the entire survey (not all did) and had not changed either shoe type or foot strike type in the previous year, and the 1363 who had made a switch in the previous year.

The specific survey question pertaining to injuries was the following:

“If an injury is defined as something that caused you to modify your training schedule for at least 1 week due to pain or discomfort (with or without formal medical care), have you experienced any lower extremity injuries in the past 12 months that you believe were caused by running?”

They followed this by asking respondents to specify the anatomical location of the injury (e.g., foot, ankle, knee, hip, etc.)

Results

Among the 904 respondents who had not switched shoe type or foot strike, 73% wore traditional running shoes, 25% wore minimal shoes (mean duration of minimalist shoe wear = 26 months), and the small remainder were primarily barefoot runners (only 16 total). Runners in the various groups were similar in mean height, age, and body mass, though minimalists were more likely to be male, had more years of running experience, and tended to report greater weekly mileage and faster training paces.

In terms of foot strike, 31% of the entire sample claimed to be heel strikers, 43% claimed to be midfoot strikers, 20% claimed to be forefoot strikers, and 6% were uncertain of their foot strike type. Barefoot and minimalist runners were more likely to self-report a midfoot or forefoot strike. The breakdown of self reported foot strike types among footwear groups looks like this:

	Foot Strike Type
Shoe Type	Heel	Midfoot	Forefoot
Traditional	41.4%	45.9%	12.7%
Minimalist	5.9%	48.5%	45.6%
Barefoot	0.0%	60.0%	40.0%

Regarding injuries, runners in traditional shoes were 3.41 times more likely to report an injury than experienced minimalist runners (46.7% vs. 13.7%). As seen in the figure below from the Army Medical Department Journal, injury percentages were higher among traditionally shod runners at every anatomical location surveyed.

Comparing injury rates among foot strike groups, rearfoot strikers reported an injury incidence of 52.4%. In contrast, 34.7% of midfoot strikers reported an injury, and 22.8% of forefoot strikers reported an injury.

As mentioned above, a large proportion of the initial survey sample was excluded from the above analyses because they had either switched foot strike (n = 866) or shoe type (848) in the previous year. The vast majority of these people claimed to have moved from heel striking in traditional shoes to midfoot or forefoot striking in minimal shoes. The main reason reported for switching was a desire to overcome an injury (40-50%). The group of 397 runners who reported changing footstrike due to injury collectively reported 500 injuries, and the 372 runners who reported changing footwear due to injury collectively reported 411 injuries. It’s not specified if these injuries include those both before and after the change, so it’s difficult to conclude whether they might all be termed “transition injuries.”

Commentary

This is an interesting study for a number of reasons, but I want to state clearly at the outset that it is based on self-reported survey responses, and as such should not be confused with a prospective experimental study. In other words, we must rely on the accuracy and honesty of the survey respondents, which opens up a lot of room for debate on the value of the findings.

Regarding this, I’ll say that I am very skeptical of the self-reported foot strike percentages. To their credit, the authors openly state this as well, and have themselves conducted a pilot study showing that only about 75% of runners accurately self-report their foot strike type, and that those claiming to be midfoot or forefoot strikers are more likely to be incorrect (i.e., at least one-third who claim to land on the midfoot or forefoot are actually heel strikers).

My own research has shown that in a large sample of traditionally shod marathon runners, approximately 90% are heel strikers. A similar percentage of heel strikers was found again in a recent analysis of foot strike patterns at the Milwaukee Lakefront marathon. Thus, the self reported heel striking frequency of 41.4% for traditionally shod runners is probably a dramatic underestimate. I also have reason to suspect that the 5.9% frequency of heel striking reported by minimalist runners is also a vast underestimate (I need to publish my data on this!). Given this, my feeling is that the high likelihood of significant self-reporting error makes the comparison of injury rates by foot strike of questionable value. The authors are very clear in pointing this out themselves, and indicate that confirmation of foot strike types would make for a more compelling analysis.

In contrast to foot strike type, one would hope that experienced runners responding to a survey like this would know what kind of shoe they put on their feet. The authors did a pilot on this as well and found that 98% of runners could correctly classify their shoe as “traditional” or “minimalist,” though the detailed criteria that they used to differentiate these categories are not provided. Given the likely higher accuracy of shoe type classification, the finding that traditionally shod runners reported 3.41 times as many injuries as experienced (> 1 year) minimalist runners is interesting. One would hope that the respondents accurately reported their injuries, and most runners should be able to recall injuries that caused them to alter their training for more than a week, but it is possible that this result is tainted by enthusiastic minimalists underreporting their injuries (the authors point this out as well). This is the reason why prospective and carefully controlled and monitored studies provide more reliable results than surveys – it minimizes bias.

If we assume that the self-reports are accurate, then this study suggests that those adapted to minimalist shoes are on average at a reduced risk of injury compared to traditionally shod runners. Lots of questions, but that’s the major conclusion. However, if you consider the fact that those who transitioned their footwear or foot strike within a year of completing the survey reported an awful lot of injuries (keeping in mind that it’s not clear whether these occurred before or after the transition), the results don’t necessarily mean that minimalist is better for all. It just means that those who make it through the transition period tend to do pretty well. It could also be a reflection of some other factor – perhaps experienced minimalists get to that point because they have inherently better form or are more injury resistant and would do fine in any kind of shoe. All we can do is speculate based on the survey reports.

Transition of any type changes stress to the body, so it’s not surprising to me that injuries are more common in this period (though another study suggested that barefoot running transition injuries are actually uncommon). The big question to me is what happens to those people who get injured in transition? It would be interesting to do a follow up and see how many of those injured during transition stuck with it, and what their longer term outcomes were like. In other words, is going minimalist and/or moving to a forefoot strike a short term risk for a long term gain? I’d also love to see a before/after analysis of form and foot strike type. Though this study raises provides some interesting results, as with any scientific paper it also raises a lot of questions. My hope is that answers to these questions will continue to appear in the coming years.

What do you think, do you believe the results of this study?

Read More