Few sporting trends have seen such a steep rise in sports popular culture as we are currently experiencing with barefoot running.  There are 2 sectors in the shoe debate with traditional footwear (shod) runners claiming barefoot running to be just the next ‘fad’ set to fall out of favour in the endurance sports world, and barefoot or minimalist runners who often possess a dogmatic belief in the barefoot method that ignores 2 key questions:  Is barefoot running even good for me?  And of course, what does the research say?  To answer these 2 questions completely we need to make sense of and summarize a lot of information, and because of this, here is part 1 of a 2 part Barefoot Running post.

How did the barefoot movement gain such popularity?

Make no mistake, there have always been barefoot runners.  In fact, much of the drive to go minimalist in footwear is based upon the millions of years of evolutionary alterations to the human foot.  In fact we have been barefoot over 99% of our existence, and shoe companies have attempted to undo this pattern with the introduction of modern footwear in the past generation (1970’s).  The real rise of barefoot running in popular media is usually attributed to Christopher McDougall’s best-selling book ‘born to run’ (an excellent book for anyone who loves sports), bringing barefoot attention to a multitude of readers.  In the past few years there has been a dramatic increase in researchers publishing a number of interesting studies on the topic, some of which we will discuss below.  The culmination saw Dr. Daniel E. Lieberman of Harvard published arguably the most prominent paper on the topic in arguably the most prestigious scientific journal in the world (Nature) in 2010 (the article is detailed below).  Now, you can hardly turn on the television, see an advertisement , or read the paper without seeing something about barefoot running.  Even the Wall Street Journal recently jumped on board!

Typically there is a concentration in the media on studies touting the benefits of barefoot running when footstrike patterns between running barefoot and shod are compared (because these studies are typically positive). However with minimal research completed on the topic, some negative results, and a lack of long term studies (particularly on if barefoot running impacts injuries), the research findings make it difficult to draw conclusions.  Of note, this hasn’t stopped many therapists, seminar leaders, and media types to jump to outlandish conclusions such as “barefoot running decreases injuries” when Dr. Lieberman himself ended his prominent paper by stating “Although there are anecdotal reports of reduced injuries in barefoot populations, controlled prospective studies are needed to test the hypothesis that individuals who do not predominantly rear RFS [rear foot strike] either barefoot or in minimal footwear, as the foot apparently evolved to do, have reduced injury rates.”  So as we often say…..let the reader beware!

What Actually Happens When Running Barefoot?: A Look At Foot-Strike Patterns

There are actually a lot of changes that occur with barefoot running.  There are kinetic and kinematic changes that occur, in addition to some apparent performance variables.  This first post will focus primarily on foot strike patterns as this is the prominent area of research concentration.

First we must define a few terms:

Fore-foot striker (FFS): land on their forefoot (ball of the heel) while running (think sprinters)
Mid-foot striker (MFS): land with a flat foot (heel and ball of the foot simultaneously)
Rear-foot striker (RFS): land with the heel first

In simplistic terms Dr. Lieberman’s paper found the following:

• Habitually barefoot runners often land on the fore-foot or sometimes a flat-foot
• Habitually shod runners land with a rear foot pattern secondary to the elevated and cushioned heel of the modern shoe.
• Barefoot runners generate smaller transient impact forces (collision force) than shod runners
• This smaller impact transient decreases the effective mass of the body that hits the ground with each stride.
• This may protect the feet and lower limbs from some injuries (we don’t know yet)

Now let’s examine how these conclusions were drawn:

It’s been found 75-80% of shod runners display a RFS pattern causing a collision (impact transient when you hit the ground and the ground exerts a vertical ground reaction force back) that is roughly 1.5-3 times your body weight that decelerates the body.  The ‘modern’ shoe tries to counter this with a large heel made of elastic materials to absorb the impact transient and spread it out over more time.

Lieberman’s study looked at 5 different groups:

1. Habitually shod amateur and collegiate Harvard athletes that wore shoes since childhood
2. Kenyan athletes from the Rift Valley Province that grew up barefoot and are now shod (most started wearing shoes late in adolescence)
3. US self identified habitual barefoot runners that are either barefoot or minimalist (Vibram FiveFinger shoes)
4. Habitually barefoot Kenyan youths that have never worn shoes
5. Habitually shod adolescents from urban primary school

Both groups that were habitually shod (group 1 and 5) RFS…..which was expected.  But interestingly, they still RFS when barefoot however did adopt a flatter foot placement by dorsiflexing (brining their toes up towards their shins) by 7-10 degrees less.  Contrasting this were subjects that grew up barefoot or switched to barefoot (groups 2 and 4) that forefoot strike in barefoot……and interestingly still forefoot strike while shod.

Why the rear foot strike in shoes?  The thickest part of the shoe is the heel. The thick heel means you end up with less dorsiflexion at the ankle before hitting the ground with each step so you end up hitting the ground with the cushioned heel.  This essentially means the modern shoe facilitates a RFS pattern.

Why does the rear foot strike seem to matter?

The simple answer is the impact transient force that occurs with rear foot running.  Think of this as the ‘pounding’ force when you hit the ground (though in truth it is a lot more complicated than that).  Lieberman showed that RFS causes tremendous impact transients in shod athletes and even larger ones in unshod athletes that RFS.  In contrast, FFS patterns lack a distinctive transient.   Check out these 2 video’s.  The first, seen below, is a shod runner;

The thing to note is the first large ‘blip’ on the upslope with each foot strike.  This is the impact transient force that is seen as a negative in those who RFS.

This second video seen below is a barefoot runner.

Note on the way up, there is no ‘blip’ on the way up at all.  This means there is a lack of impact transient.  Both of these videos are found on Dr. Lieberman’s website (which is fairly awesome by the way).  Overall, the peak vertical force of impact was found to be about 3 times lower in barefoot runners than shod who RFS.  This work is contentious however.  Support is seen in some research (for the most part) – see Divert et al, while others (like the next study discussed) don’t support a loss of impact transient, just a lessening.

The second factor is the rate of loading.  When running with a FFS, the rate of loading is about 7 times lower than shod runners who run with a RFS when barefoot and twice as low as RFS while running shod.   If you’re attentive you’ll note that there is a HUGE difference when a shod runner runs with a RFS and that same shod runner goes barefoot and adopts a RFS pattern.  Essentially if you are running barefoot with a RFS pattern, the potential benefits cited above are lost and in fact the impact transient is increased.

What about those Vibram 5-Finger Shoes?

These shoes were initially manufactured as yacht deck shoes, hence why they have the clingy rubber grips on the bottom.  Once adopted for running they are now touted as providing a layer of protection just enough to run ‘barefoot’ without worrying about puncture wounds, cuts and bruises.  An interesting study by Squadrone compared the vibram 5 fingers (VF) with traditional shoes and barefoot running.  In terms of impact transient forces, the VF shoe more closely mimics the barefoot condition vs the shod one.  However, the Squadrone study did show an impact transient for all 3 conditions (VF, shod, and barefoot) which contrasts the Lieberman study (albeit the barefoot and VF were substantially smaller then the shod one).  The study methodology was substantially different whereby a treadmill was utilized and it was the same runners for all 3 conditions (Lieberman’s put a force plate 80% of the way along a 20-25m track).  Further, training for the 3 conditions was only allowed for a period of 10 days prior to the data collection so you could argue that the subjects weren’t properly habituated to each condition.

Of note, the VF were not entirely similar to the barefoot condition.  Step time was found to be higher and stride frequency lower when wearing the VF.  Additionally, the thrust peak vertical force was higher meaning someone wearing a VF could push more vigorously then barefoot with each stride (thought to be due to the rubber sole).  In fact running with VF required less energy than running barefoot via VO2 values.  Does this mean vibrams are better?  No!  In fact, the evidence was conflicting with certain variables closer to shod and others closer to barefoot.  Also, the sample size of 8 is too small to draw definitive conclusions from.

Where to go from here

It’s exhausting breaking all of this research down.  Stay tuned for a second post on performance.  This will touch on kinematic changes in your actual joints that occur with barefoot running including something called stiffness adaptation and how your foot, ankle, and knee actually adapt to running barefoot.  We will also touch on oxygen demands, stride rate and frequency………oh ya, and we will attempt to draw some conclusions!

One last thing to leave you with (also from Dr. Lieberman’s website): A Kenyan adolescent runner that has only run barefoot…..without trying to apply all that we have learned so far, just watching it is pretty neat to see how seemingly effortless running is for this guy!