August 1, 2016

Our ancestors ran in bare feet or very thin shoes with little padding. It's undeniable, it's been proven over and over again in historical research, and probably the best guy on the face of the planet to give insight into this fact is Dr. Daniel Lieberman from Harvard (with whom I had the pleasure of running 8 miles barefoot through Boston a couple years ago).

In today's article, you're going to learn why you need to learn to run barefoot or in minimalist shoes (if you're not already), how train your feet to withstand the rigors of barefoot running, and a simple method to trick your body into flawless barefoot running form, even if you've never run barefoot.

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What The Research Says About Barefoot or Minimalist Shoe Running

It wasn’t until the 1970’s when conventional running shoes with thick cushioning soles became widely available.  It was thought that the cushioning effect of the padded heel would decrease loading on the legs and therefore prevent injury while at the same time increasing efficiency. But since then, there has been a big shift in thinking for many runners, and many are now removing their shoes in order to return to what they believe is a more natural gait.

Why?

Cushioned running shoes promote a rear-foot strike (RFS) running pattern in which the heel touches down first, then the foot rolls forward for toe off.   Habitually barefoot runners, on the other hand, tend to land on the forefoot or mid-foot.  These differences in stride mechanics drastically affect injuries, as well as running efficiency.

For the purposes of this article – and to make me sound much smarter than I am – when I refer to running in cushioned shoes, I will use the term “shod” (this is also a great word to impress any runners at cocktail parties). Furthermore, when I refer to barefoot running, this would also include running in shoes such as Vibrams or extremely minimalist, relatively uncushioned shoes. 

Oh yeah, one other thing: if your eyes glaze over from research and nitty-gritty science, or if reading time is tight for you, feel free to skip this section and scroll down to the next section. 

There are many mechanical differences seen during barefoot running when compared to shod running – the most obvious being foot strike position.  When shod, runners tend to land on their heel in a rear-foot strike (RFS).  Without shoes, the foot is in a much different environment and this same heel landing can be painful and damaging to the foot and leg. For this reason, barefoot runners often adopt a forefoot strike (FFS), in which the front of the foot contacts the ground first and the supporting soft tissue of the foot and lower leg absorb some of the impact force before the heel even touches down.  A mid-foot strike is also seen in many barefoot runners, in which the foot lands relatively flat on the ground.  This change in foot strike pattern is absolutely correlated with a lower impact force upon foot strike.

In the article “Foot strike patterns and collision forces in habitually barefoot versus shod runners“, Daniel Lieberman studied impact forces and stride mechanics of habitually barefoot and shod runners running in both bare feet and shoes.  The purpose was to see how the shoe directly affected impact forces and stride, and also to see how habitual shoe use changes running patterns and get an idea of how man ran before the advent of the cushioned shoe.

There were five test groups in this study:

(1) Kenyan competitive runners who grew up barefoot and recently started wearing running shoes.

(2) habitually shod American adults.

(3) American adults who grew up wearing shoes but are now habitually barefoot runners.

(4) habitually shod Kenyan children.

(5) barefoot Kenyan children. 

Foot strike kinematics were assessed using video analysis as test subjects ran at an endurance running pace (4-6 m/s) on a short track.  All the adults sampled ran at least 20 km per week.  It was found that American habitually shod runners ran exclusively with a rear foot strike while wearing shoes and nearly all (87%) ran with a rear foot strike when barefoot.

During the barefoot test, the subjects in this group, while still landing with a RFS, had less dorsiflexion (7-10%) upon ground contact (meaning their forefoot was closer to the ground).  The recently shod Kenyan competitive runners (1) had a 91% rate of FFS when running barefoot and 54% while wearing shoes, many who didn’t FFS were landing with a MFS.

The last group of adults tested was Americans, who grew up shod but switched to and are now habitually barefoot runners (3) in which 75% FFS when barefoot, but when shod 50% ran with a RFS.  They also tested Kenyan children who were habitually shod (4) and who have never worn shoes (5).  The children’s running habits were consistent with what was found for adults, mainly that the use of running shoes significantly changes the gait pattern both immediately and also habitually.

The study also analyzed strike force characteristics, comparing habitually barefoot and shod adults from the US in both shoes and bare feet.  It was shown that RFS causes a large impact force transient upon ground contact in both the shod and barefoot condition, but it was even larger when barefoot.  FFS on the other hand showed a steady force loading with no impact transient.  The barefoot FFS runners had a lower vertical force magnitude during impact, as well as a lower loading rate – which was very significant when compared with barefoot RFS runners.

In sum…wearing cushioned running shoes automatically causes you (even if you're used to running barefoot) to engage in a high impact heel strike. 

There are a few reasons why running shoes promote this type of RFS.  First, they have a thick heel padding that orients the sole of the foot to have about 5^o less dorsiflexion than the outsole of the shoe, encouraging RFS.  This means that in order to FFS while wearing a thick heeled shoe, you would have to plantar flex (point) the foot significantly. The shoe also affects foot strike, due to the cushioning properties which help absorb the impact force from running. Finally, shoes actually decrease neural sensory stimulation that promote a softer FFS.

The study above shows that habitual running patterns are influenced by footwear use, but just how these adaptations occur and their effect on injuries is unclear from the study.  However, the article “Running Related Injury Prevention through Barefoot Adaption” looks into the foot musculature and how it responds to barefoot conditions.  The authors of the article state that many people believe the high injury rates involved with running are because the foot is fragile and cannot take the strain that activities such as running puts on it without injury, and therefore that foot needs protective support.

Problem is, this theory not only goes against natural selection, but also has been proven wrong based on the lower running injury rate seen among barefoot populations.

In countries where both barefoot and shod population live, such as Haiti, high rates of lower extremity injuries are only seen in the shod population. Likewise, in countries where people go barefoot part or all of the year, such as the West Indies, and sections of Europe and Asia, there is shockingly little report or evidence of impact related lower leg injuries.

Because of this, Robbins and Hanna, authors of the article above, hypothesize that the weak arch and foot musculature seen in habitually shod feet can be strengthened given the right conditions.  The human foot has a large arch in the middle that can act as a spring which absorbs and restitutes mechanical energy.  The arch is supported by the plantar fascia and several ligaments and muscles.  The arch works almost like a bowstring, and if it is shorter in the longitudinal length of the foot, it will be higher and able to absorb more energy.  These muscles controlling the arch are not stimulated properly in shoes, but can be strengthened by barefoot activity, therefore increasing the arch height.

To test this hypothesis, Robbins and Hanna recruited recreational runners and examined the length of their medial longitudinal arch with x-ray analysis and a foot imprint during weight bearing, monthly over the four month test period. Subjects gave a detailed running history that included footwear, injuries, and previous barefoot weight bearing activities. During the experiment, subjects kept a detailed training log that recorded all barefoot weight bearing activity – including running, walking, and standing, as well as the surface it was performed on –  and they were instructed to perform as much barefoot activity as possible.

The study reported a positive change as a 1mm shortening of the medial longitudinal arch length.  It was found that of the 18 subjects in the barefoot group, 13 had a positive result, 2 had no change, and 3 had a negative result, with an average arch shortening (meaning a stronger arch) of 4.7mm.  In the control group that continued normal activity, 1 changed positively and 10 negatively with an average arch lengthening (meaning a weaker arch) of 4.9mm.  The results had no correlation with the starting height of the arch. The positive result on the arch of the barefoot group can be explained by an increase in the supporting musculature, which clearly shows that adaptive abilities of the foot to change and strengthen to accompany its environment.  Strengthening of the arch and shortening of its length could also reduce injuries like plantar fasciitis, which is common in shod populations. This is because the plantar fascia would be stretched and therefore stressed less, as some of the load would be diverted to the musculature.

It was found that the best arch change results happened with high total weight bearing activity (i.e. standing), walking outside barefoot, and running outside barefoot. It makes sense for results to show this with an increase in total load bearing activity because the muscles simply got more use.  The reason outdoor (compared to indoor) barefoot activity had a positive effect is because of the irregular surface, which would increase plantar sensory feedback.  Interestingly, the skin on the top of the arch has a much lower pain threshold than that of the heel or toe area and if this area is stimulated, the arch muscles could contract to make barefoot running (or other activity) more comfortable, while at the same time activating the foot’s shock absorbing system.

The skin on the plantar surface of the foot has one of the highest density of neuroreceptors in the body.  The receptors respond to small discrete displacements, shear forces, and vibrations, all of which are reduced by footwear, specifically running shoes.  Running shoes block the transition of sensory information to the foot which tells the runner to lower ground impact forces by flexing the arch muscles and changing stride mechanics.  This would not be a problem if the shoe reduced the injury producing ground impact forces as much as it reduced plantar sensation, but that is not the case as shown by the Lieberman, and the increased running injuries seen in the shod populations compared to barefoot.

So far, we've seen that research shows barefoot or minimalist shoe running causes some pretty useful adaptations in terms of foot strike pattern, “feel for the ground”, and reduced risk of lower extremity injuries.

And there's plenty more…especially when it comes to reduced injury risk from the avoidance of cushioned shoes. study called “The effect of running shoe on lower extremity joint torque” examined the effects that shoes have on the leg joints when compared to running barefoot.  The subjects in this study were 68 young healthy adults who ran at least 15 miles per week.  Markers were placed on various spots on the subjects' legs, and data was collect by 3 dimensional video analyses, as well as a force place on the treadmill they were asked to run on.

For shod running, there was a 54% increase in hip internal rotation torque, 36% increase in knee flexion torque (which acts on the main bending motion of the knee), and a 38% increase in knee varus torque (which is a lateral bending force at the knee). The relevance of this data is how it relates to joint degeneration and osteoarthritis risk, as well as overuse.  Osteoarthritis is joint cartilage degeneration and ossification and is correlated with long term excessive loading.  It has been shown that competitive running may increase the risk of developing osteoarthritis in the hip, therefore producing over 50% more load on the joint with each stride.  The increase in knee flexion torque would increase the load on the quadriceps, thus increasing strain on the patellar tendon and pressure on the patellofemoral joint, which can lead to overuse injuries of all these structures.  The increase in varus torque on the knee would increase the compressive force on the medial tibiofemoral compartment, which is more prone to degeneration than the lateral compartment.  Similar yet less dramatic increase in knee loading were seen when comparing women’s dress high heeled shoes when walking with barefoot walking.  Because of the higher rate of knee osteoarthritis in women and the fact that loading is much higher during running than walking, this increase in knee force could easily lead to osteoarthritis.  The increased loads were thought to be due to the elevated heel and material under the medial aspect of the foot, which changed running mechanics.  These increases in loading seen in shod running could all over time contribute to the onset of osteoarthritis.

Yep, as ironic as it may seem, wearing giant pillows around your feet actually increases your risk of things like arthritis later in life.

Along with reducing injuries, barefoot running is also thought to be a more metabolically efficient way to run, and the very recent study “Barefoot Running Reduces the Submaximal Oxygen Cost in Female Distance Runners” definitely backs this up. It has also been shown that an increase in of 100g of mass per foot increase metabolic cost by 1%.  This mass effect can be an especially big factor in racing, because if a typical 250g shoe was worn, it would add 5% to the metabolic cost, therefore slowing a runner by 5%.  This means a 4 hour marathon could see a change of around 12 minutes just from the weight of footwear.  It is clear that mass has a large effect on energy use while running, but it is theorized that the elastic properties of the arch and lower leg musculature also have an effect.

The article “Barefoot-Shod Running Differences: Shoe or Mass Effect?”  looked to determine if it was just the weight of wearing a shoe that made it less efficient, or if it was the shoe itself and the effects on stride mechanics. In this article, 12 healthy adult males with competitive running experience ran on a treadmill barefoot, in 50g, 150g, and 350g socks, as well as 150g and 350g shoes for 4 minutes at 13 km/h.  The mass on the sock was distributed in the same manner as that of the comparable weight shoe.  It was found that the bare sock (50g) produced no significant difference in running pattern compared to fully barefoot, showing that the results will not be altered by the effect of the material of the sock.  The treadmill had a force plate to measure vertical and anterior-posterior ground reaction force.  During the trials, the subjects exhaled gas was collected to determine the volume of oxygen (VO₂) consumption relative to total mass, which tells how hard their body was working to maintain their running pace.

While un-shod, 9 of the 12 runners switched to a forefoot strike pattern.  It was found that VO₂ consumption increased as shoe mass increased, but was not affected by the mechanical properties of the shoe.  It was also shown that total work increased in the barefoot condition.  As a result of the increased work, but no increase in VO₂ consumption, it was concluded that the net mechanical efficiency of barefoot running was greater than shod running.  This agrees with the hypothesis that barefoot running, and subsequent FFS, allows the foot and leg to use their natural elastic properties to absorb and restitute mechanical energy from ground contact.

The previous study had two variables – shoe padding and foot strike – which made it difficult to interpret the results.  To account for this, the study “Metabolic cost of running barefoot versus shod: Is lighter better?”  was similar, but it controlled foot strike pattern as well as weight, so that the cushioned shoe was the only variable.  The test subjects were 12 runners with extensive barefoot experience who had a mid-foot strike not only when running barefoot, but also when shod.  The subjects all ran at least 25 km/week, with at least 8km barefoot or in minimalist footwear.  The participants ran on a treadmill with a force plate at 3.35 m/s.  Oxygen consumption (VO₂) data was collected.  The shoes used only added cushioning and had no arch support.

It was found that in both shod and barefoot conditions, oxygen consumption increased by 1% per 100g added per foot.  Also, on average a 3-4% increase in VO₂ consumption was found during barefoot running compared to shod running of equal weight and foot strike pattern.  This shows that factors other than shoe mass play an important role in the metabolic power used during barefoot versus shod running.  This difference can be due to shock absorbing characteristics of the shoe and a difference in stride length, which was found to be 3.3% greater during shod running.  It was estimated that the 3.3% increase in stride length would only account for less than 0.4% increase in metabolic savings. Because of this, the researchers concluded that of equal mass, the cushioning properties of the shoe account for the majority of difference in VO₂ consumption.  This is because during barefoot running, all the cushioning is done by the action of the leg, which is accomplished through muscle contraction, thus expending energy.  By wearing a cushioned shoe but not changing general stride mechanics, the runner was essentially running on a softer surface while keeping the beneficial forefoot stride, which turned out to easier on the leg muscles and more efficient for the body.  The study also found that a light weight (about 130g) cushioned shoe is equally as efficient as fully barefoot running when stride is constant, which means minimalist running shoes could be a good alternative for barefoot runner while running on very hard surfaces or during a long race.

Yeah, that's a mouthful, but basically it means that a minimalist shoe, or some other method of causing one to engage in a front foot strike, could be just as good as running barefoot when it comes to running efficiency and economy.

Overall, it's very obvious that barefoot running seems to be beneficial in many aspects of running. The majority of benefits of barefoot running come with adopting a better running stride, which is characterized by a forefoot strike.  This reduces the load and loading rate during foot impact, which can lead to many running injuries, including plantar fasciitis, patellofemoral joint pain syndrome and osteoarthritis.  But the benefits of switching to barefoot running are not all immediate.  The muscles of the foot and lower leg become very weak from underuse when constantly shod, and it takes time for them to regain their strength, as well as for the body to change running technique.

However, once the transition is made, the stride will become more efficient with a reduced risk of injury. With regards to running efficiency, the cushioning from the shoe is beneficial, as well as the elastic properties of the forefoot strike. For best efficiency, a runner would want to become proficient with barefoot running, which will improve forefoot strike and cause a strengthened arch, and then wear a very lightweight moderately cushioned shoe for a race.

Although barefoot running has been shown to reduce injuries, injuries are also very common among new barefoot runners.  People hear about the benefits of barefoot running, then jump into barefoot or minimalist running much too quickly, without proper adaption.  As shown from the studies above, the muscles and soft tissue take months to strengthen, so increasing volume too fast is very likely to cause a problem.  Also, even though the loading is lower during barefoot running, metatarsal stress fractures are common. Because the bones in the foot don’t get the same loading pattern during shod rear-foot strike, they will take time to adapt to this new running style as well.

Finally, there are reports of injuries from barefoot and minimalist runner who do not adopt a forefoot strike.  As discussed above, rear-foot strike without a cushioned shoe causes very high force loading rates of the foot and leg, which could quickly result in injury.  In conclusion, more research still need to be done on the topic, but it seems clear that there are a multitude of benefits to barefoot running, and they should not be ignored.

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Heel Striking Isn't Always Bad

Even though an RFS (remember, that's a “rear foot strike) and a heel striking motion is associated with higher risk of injury, if you're landing softly (as barefoot running trains you to do) even heel striking motion that isn't necessarily always a bad thing.

A New York Times article from a couple months ago entitled “Why We Get Running Injuries (and How to Prevent Them)” delves into this idea in greater detail. Among other clues that the human body was meant to run minimalist, the article states that…

“…The never-injured runners, as a group, landed far more lightly than those who had been seriously hurt, the scientists found, even when the researchers controlled for running mileage, body weight and other variables. That finding refutes the widely held belief that a runner cannot land lightly on her heels.”

The article goes on to describe one of the runners studied, a woman who has run multiple marathons and never been hurt, showing some of the lowest rates of foot loading the researchers had ever seen, pounding far less than many runners who land near the front of their feet, with a beautiful running motion that was like seeing “an insect running across water”.

It's important to note that this woman was running with a heel strike but she was running softly even with that heel strike, which she was able to do because she had trained minimalist and trained barefoot, which teaches your body how to (even if you're not engaged in a mid to front foot strike) run with far less impact to any part of the foot that hits the ground.

In other words, once you swear off the cushioned shoes, you run more softly and with reduced risk of injury, even if a fancy high-speed video camera shows your running form doesn't significantly change with regards to a front vs. mid vs. rear foot strike.

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How To Train Your Body To Run Barefoot

Convinced that you may want to start moving away from cushioned shoes and ready to start training to run barefoot?

In the article, “How To Start Running Barefoot“, I get into the nitty-gritty details of how both my wife and I transitioned to minimalist shoes and barefoot running. Some of the biggest takeaways from that article – aside from not simply rushing out and beginning to run oodles of miles in a brand new set of Vibrams – include the following five tips:

1. Do Drills. As part of the short runs that you start doing barefoot, also train your body how to run with good form by including running form drills, such as playground style skipping, the toe-up drill or the lean drill. These drills will help ensure that you’re running efficiently and striking the ground properly as you learn barefoot running, and are a good idea to incorporate whether or not you’re running barefoot. Here is an overview of even more drills from my friend and Australian running guru Graeme Turner.
2. Feel The Ground. If you’ve been wearing big, bulky, protective shoes for a long time, then your foot may have difficulty properly sensing the ground when you run barefoot. So try incorporating “feel-for-the-ground” activities like standing on one leg when you’re brushing your teeth, standing on one leg while on a balance disc or balance pillow at the gym, standing on one leg for exercises like overhead presses, or even bouncing on one leg on a mini-trampoline a few times a week.
3. Get Flexible. One of the most common complaints among people who transition to barefoot or minimalist running is that their calf muscles and Achilles tendon feel tight or painful, and that was certainly the case when I made the transition to barefoot running. So as you make the transition to barefoot running, also work on the flexibility of the back of your legs by doing calf stretches and foam rolling for the back of your legs.
4. Get Strong Feet. If you’re worn shoes your whole life, it’s likely that you have weak feet muscles, since one of the primary functions of a shoe is to provide your foot with extra “muscle”, or support. While some of the balance activities mentioned earlier will help to strengthen your foot, I also recommend standing on one leg and practicing rolling your entire body weight from the outside of your foot to the inside of the foot and back, until your foot is tired. When at the gym, it can also be helpful to do cable kick forwards and cable kick back exercises while standing on one foot. If your tiny foot muscles start to burn and fatigue with these movements, you’ll know you’re conditioning your foot muscles.
5. Include Plyometrics. Your feet need to be conditioned to withstand the impact of the ground, since the cushioning of a normal shoe provides significant impact reduction benefits. Plyometrics are explosive exercises in which hop, bound or skip with one leg or two legs, and good choices for barefoot running preparation are side-to-side hops and single leg jumps onto a box.

For more details, you can click here to read that article in full.

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The Best Barefoot Running Orthotic & A Simple Method To Teach Yourself How To Have Flawless Barefoot Running Form

Lately, I've been using a new method to get “the best of both worlds”: meaning getting the front to mid foot strike that I automatically shift to when barefoot running, while still getting the protection afforded by actually wearing shoes, which comes in handy when I'm doing Spartan races, TrainToHunt competitions, triathlons or other events where I actually do need protection for my feet.

The method is something called a “ShoeCue”.

The Cue inserts into your shoe just like an orthotic, and it uses a textured, thermoplastic heel-plate that reconnects your feet to the ground. With vibration and texture, it “wakes up” the soles of your feet and reconnects them to your brain. Closing this neural loop allows for enhanced control and understanding of how you are connected to the world, and in real-time it improve self awareness and proprioception, whether you're walking or running.

Here are a couple videos that show how the ShoeCue works (and yeah, that's Brian Mackenzie in the first video, the guy I interviewed here about advanced breathing techniques):

 

Basically, the Cue restores sensory feedback to your foot, which you've learned is usually diminished when you wear your shoes. The soles of your feet are one of the most sensitive areas in your body, and your brain relies on the sensory perception to control everything about about the way you move. By increasing sensation to your feet with these Cues in your shoes you will:

-Be more aware of your running technique and run with a softer foot-strike.
-Have greater positional awareness while lifting and exercising.
-Walk and stand with better posture.

The nerve receptors in skin on the soles of the feet pick up sensation in three main ways:

-Indentation
-Shearing force
-Vibration

All of these mechanics your body relies on to feel the ground are blocked by a traditional shoe when compared to being barefoot, but ShoeCue is able to restore this sensation, in virtually any shoe.

So what should you expect to feel when wearing these things?

You will certainly notice the Cue, but it is in no way painful. It feels like a gentle massage on the bottom of your foot. The goal is not to create pain when you are moving poorly. The goal of the Cue is to simply increase your bodies positional awareness and subtly encourage better biomechanics over time. When you put them in your shoes, you'll notice an immediate reduction in over-striding and heavy heel strike (which you now know are major contributors to running injury and joint wear). Every time I run in these, my stride feels softer, smoother, and more efficient. Also, as fatigue sets in on a hard run, I'm a bit more aware of any breakdown in running form and able to self correct in real-time.

And these are definitely a bit different than traditional arch support orthotics. Arch support works to lift your arch and hold it in a static position. This may be better than walking around with collapsed arches and flat feet, but it does not address the underlying strength and motor control issues, which are the root cause of the problem. By increasing sensation to your feet, ShoeCue encourages the small muscles in your feet and ankles to be active, just like when you run barefoot, and when your arch does collapse, you will feel it and be able to consciously turn on those muscles and move better.

I'll warn you that ShoeCue encourages you to favor the ball of your foot as opposed to the heel. When this happens, you will be stressing muscles and tissues in the lower leg that have been underused, and you may experience soreness after your first few runs – so start with shorter runs, give it time, and progress slowly, but in my opinion, it's well worth it to add these to your running, walking and standing repertoire as a very cool biohack to get you to begin running with the same flawless form you'd develop from barefoot running, but with the actual protection of shoes.

You can try these new running orthotics here, and use 10% discount code Greenfield10. I've got a set in all my own running shoes now, and it's a perfect way to start running “barefoot”, without actually running barefoot.

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Summary

So what do you think?

Do you run barefoot or in minimalist shoes, or do you have yet to be convinced of the benefits?

Do you have questions about “barefoot running orthotics” like the ShoeCue?

Do you think I'm completely wrong and that big, built up cushioned shoes are the way to go?

Leave your comments, thoughts and feedback below and I'll reply! Finally, you can click here to get yourself a set of ShoeCues, and use 10% discount code “Greenfield10”.