A few weeks ago there was a class-action settlement by Vibram for false claims that its barefoot running shoes could reduce foot injuries and strengthen foot muscles. Hot on the heels of this case Vivobarefoot have a new sales campaign advising:
‘Don’t run in our shoes’- Unless you have strong, healthy feet and good technique (http://www.vivobarefoot.com/eu/discover/get-involved/barefoot-blog/may-2014/do-not-run-in-our-shoes)
They then go on to say ‘The science behind barefoot running is indisputable.’ quoting studies that conclude forefoot striking (FFS) and shorter stride length can significantly reduce loading rates and reduce the risk of injury.
Now I like to wear Vivobarefoot breatho shoes to work. They are wide and most importantly allow my feet to breath, I even occasionally run in them. But I’m afraid that their quoted science in support of Barefoot style running is VERY disputable. In fact it is in the nature of science to question, dispute and prove theories. To balance the argument, here is a little more ‘disputable’ science everyone wishing to run in barefoot shoes should be aware of.
Scientific evidence does not support claimed manufacturer benefits of barefoot running shoes (BFS) and indicates BFS running may be a precursor to some injuries-particularly stress fractures.
Much of the pro-barefoot quoted science is based on evolutionary theory that man is adapted to run barefoot or in supple shoes with no cushioning . Now I’m sure EVA midsoles weren’t around a few thousand years ago but nor is it likely that the whole tribe went running around chasing antelope. Those most fit for hunting were the ones most likely to perform this task. It is evident even today in some primitive tribes that not everyone in the village gets to join the hunting party. So it’s more likely that SOME were adapted well to running barefoot after prey, the others probably stayed home and collected berries. I’m not sure we were all ‘Born to Run’ bare foot, at least not for long periods.
Were we all ‘Born to Run’ barefoot?
Another often quoted study in the barefoot running library states that the majority of habitually barefoot people run with a forefoot or midfoot strike . The barefoot Kenyans in this study were all from one area, the average age of subjects was around 14 years and they were running at a speed around 20kph (Fig. 1). The 8 subjects from the USA were running over 14kph. Hardly comparable with most of us jogging along at 10-12 kph.
Figure 1. Barefoot Kenyan adolescent. Sprinting strike pattern
For the video see https://www.youtube.com/watch?v=pgkWhcapWLU
Another more recent study looked at another group of Kenyans of varying ages and over a range of speeds . This study showed that not all habitually barefoot people prefer running with a FFS and the majority (around 80%) of subjects instead used a rearfoot strike (RFS) at endurance running speeds. Percentages of midfoot (MFS) and FFS increased to around 50% only with speeds greater than 18kph. (Fig 2).
Fig 2. Frequency of foot strike patterns compared to running speed of Daasanach tribe (Hatala et al, 2013)
Hmmm… Looks like habitually barefoot runners only transition to a FFS when they’re of adolescent age and sprinting. This may also explain why we see many runners with barefoot shoes (BFS) landing on the heels - because it’s totally natural to run this way.
Heel striking is natural when running barefoot
The most commonly quoted benefit for running in BFS is that heel striking is bad due to increased impact and that the impact point is the most injurious part of the gait cycle. (Fig. 3)
Fig. 3. Impact transient heel strike vs forefoot strike (Lieberman et al. 2010)
Well I hate to break the news but this ‘indisputable science’ is again ummm… how shall I say this delicately …… completely disputable.
I came across a poster presentation a few years ago stating there may be two different foot strike strategies for reducing shock. One involves a RFS and the other a FFS (13). It appears that at lower speeds a RFS may reduce loading rates and at higher speeds a FFS may do the same (Fig 4). I have to wonder why we never heard more about this study. Regardless of the reasons, this would be regarded as a low quality study and a great example of how disputable science can be. It hints at different strategies to reduce shock but proves nothing.
Fig 4. (Bowser et al. 2011)
Another more robust study showed a FFS actually increases peak vertical Ground reaction force (GRF) and significantly increases tibial acceleration (14) which is associated with increased risk of tibial stress fracture . This tells us that tibial stress fractures may be related to impact (higher with RFS) or tibial acceleration (higher with FFS). It is still unclear which of these is most important but as both foot strike types can increase these variables perhaps it is another variable such as knee stiffness that is more important than footstrike .
Is Impact related to injury?
Of more importance is the lack of evidence linking running impact to the most common running injuries. One leading researcher concluded theoretical, experimental, and epidemiological evidence on impact forces show that impact forces are not important factors in the development of chronic and/or acute running-related injuries 
There may be a relationship of impact to tibial stress fractures but it is unknown if impact alone is responsible or other biomechanical factors are also at play. Tibial stress fractures are a relatively rare running injury but the evidence to date suggests that impact is not responsible for the majority of running injuries.
Of particular interest to those wearing Barefoot shoes is a recent study which showed greater bone marrow oedema in the feet of subjects using Vibrams after 10 weeks of running . The anti-barefoot brigade were super quick to jump on this one stating that bone marrow oedema was a pre-cursor to injury (Fig 5).
Fig 5. Imaging in Sports Medicine www.msdlatinamerica.com Image shows intense marrow edema of second metatarsal. Low signal intensity stress line and cloudy periosteal reaction (arrows) are evident.
However, bone marrow oedema is a natural asymptomatic stress reaction and is believed to lead to stress fracture only if sufficient rest does not occur between successive stress incidents. Provided enough rest occurs between runs the bone remodels and becomes stronger. This is known as Wolfe’s Law, ‘Bone remodels occurring to the forces placed upon it ’. In other words ‘Take it easy’. The adaption time for the foot bones when wearing barefoot shoes looks like it takes longer than we all initially thought. There is also a growing body of evidence that plantar heel pain in runners may be impact related but like most injuries we find there are normally other contributing factors ( such as reduced ankle or big toe dorsiflexion, increased body weight).
The bottom line is:
Transition VERY Slowly!
So what about changes in muscle activity?
Muscle recruitment patterns are altered by midsole hardness . Even though the hardness of the shoe may initially increase impact, the body adapts to this by changing muscle activity to allow greater absorption of this impact and this activity is altered over time according to the impact task at hand. i.e. Harder surface leads to softer knees.
This is a great example of our on-board computer adjusting the suspension to give us an optimal ride if the tyres are too hard. Problems arise however when fatigue starts occurring.
There is some evidence that barefoot style (BFS) running may be more efficient as oxygen consumption is decreased when running on stiffer surfaces  and minimally shod runners are modestly but significantly more economical than traditionally shod runners regardless of strike type . But what happens when we get fatigued?
When given the choice of comfortable joints or comfortable breathing, the body seems to prefer comfortable breathing. When metabolic cost becomes an issue the body makes it easier for the heart and lungs at the expense of the joints and muscles. These in effect become stiffer to use up less energy in shock absorption. (It takes less effort to let your knees bend a little than let them bend a lot).
What this means is that barefoot shoes initially make life easier for running i.e. more economical. Oxygen consumption is less and running feels easier (at least to the cardio-vascular system). The initial increase in impact is sensed by the body which adapts by softening the hips, knees and ankles. However, as the run progresses and fatigue starts setting in the body wants to make life easier on the heart and lungs. It does this by stiffening the muscles and joints. (As there is less metabolic cost with stiffer joints). You can see how the initial reduction in joint stiffness to cope with impact is lost. Joints stiffen up and impact increases once again.
With fatigue, impact increases
Does this combination of increased impact and reduced muscle compliance to absorb this impact contribute to injury? We don’t know. It seems likely but that is not scientific proof. We know that softer running shoes increase torque around the knee compared to BFS running  which may also be related to injury. We also know that cushioning is initially effective in reducing peak impact force and tibial acceleration at initial foot-ground contact  but this effectiveness is most likely lost with time as the body adapts to the surface it is running on.
It all seems to depend on the body’s ability to absorb these forces which lessens with fatigue.
To be safe:
Avoid becoming fatigued when running in Barefoot Shoes
As a clinician I’ve seen a few more stress reactions in the feet of BFS runners but we see these in others as well. This is mostly due to lack of rest rather than particular style. I’ve not seen the Achilles tendon problems that are often claimed nor have I seen the research linking barefoot style running to this injury (see here for more on this). The most common complaint has been calf pain. This normally resolves with strengthening exercises and time.
Like many others I went through the barefoot transition process a few years ago and reverted back to a cushioned shoe with lower heel after a few months. It was simply more comfortable. I find BFS running great as a tool to teach people about where the foot is landing but not as an End Goal. I also use it sparingly to encourage more spring when this is lacking.
Does BFS running encourage strong healthy feet?
Yes- with moderation and:
No – with overuse
(Just like all other running styles)
Do you need good technique to run in Barefoot shoes?
Yes- If you are doing a lot of BFS running but probably not the forefoot/midfoot technique commonly taught. Other factors are likely more important such as hip action, knee flexion and direction of GRF (See here for general pointers).
No- If you’re only doing a little. Your technique will adapt accordingly.
(Just like all other running styles)
If you’re interested in other more scientific perspectives on BFS running and the Vibram court case see these other great posts.
Natural Running Center: http://naturalrunningcenter.com/2012/04/04/class-action-lawsuit-vibramfivefingers-merit/
If you’ve been injured with Barefoot style shoes share your story so we can see if certain patterns develop to help guide our advice and treatments.
inFORM and Stay inFORMED
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- Lieberman DE, Venkadesan M, Werbel WA, Daoud AI, D'Andrea S, Davis IS, Mang'eni RO, Pitsiladis Y: Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 2010, 463(7280):531-535.
- Hatala KG, Dingwall HL, Wunderlich RE, Richmond BG: Variation in foot strike patterns during running among habitually barefoot populations. PloS one 2013, 8(1):e52548.
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- Kerrigan DC, Franz JR, Keenan GS, Dicharry J, Della Croce U, Wilder RP: The effect of running shoes on lower extremity joint torques. PM & R : the journal of injury, function, and rehabilitation 2009, 1(12):1058-1063.
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13. Bowser B, Fellin R, Davis I. Kinematic Strategies Used by Runners to Reduce Tibial Shock Following Gait Retraining. Poster. American College of Sports Medicine. Jun 01, 2011
14. Laughton, C.A., Davis, I.M., & Hamill, J. 2003. Effect of strike pattern and orthotic intervention on tibial shock during running. Journal of Applied Biomechanics, 19, 153-168