The barefoot running debate:

the latest scientific thinking

There are more than a few people who have dismissed barefoot running as a fad. And many will have labelled it a niche concept, practiced by a very small percentage of runners. That's only partly true. If you think that barefoot running has nothing to do with you, think again. Your customers may not have discarded their shoes, but the truth is the shoes you are selling have already been influenced by the concepts that drive the barefoot running movement.

During the last decade, which has seen more and more evidence come out AGAINST shoes, has also seen a shift in the shoe industry. Gone are the heavy, bulky motion-control shoes, replaced by shoes that are now marketed to simulate barefoot running.

I remember adidas bringing out "feet you wear" in the 1990s, but it was the Nike Free that was the first "barefoot shoe" said Irene Davis in her ACSM presentation. She told the story that a famous US college coach told a Nike rep who had come to watch his team train that his runners were more comfortable being barefoot. The rep rushed back to HQ, reported on the athletes' preference, and it heralded the shift.

Now, almost all the companies are focusing on the minimalist concept of shoes. There are even new footwear companies that focus on these shoes (e.g. Vibram, Innov8, Newton).

Of course, there are a few stubborn survivors, but there is no doubt that the whole market has shifted. Why? Because of the current thinking around running, and the role of footstrike in injury risk during running. All runners are affected, even those who run in shoes. And here's the theory.

The Born to Run theory

Barefoot running is fascinating because it has made such a big impact in the mainstream. And a big part of that is the book Born to Run, by Christopher MacDougall. It traces the story of the Tarahumara Indians, and contains chapters dealing with the work on barefoot running — US biomechanist Irene Davis and Daniel Lieberman, professor of Human Evolutionary Biology at Harvard, have starring roles.

The fundamental premise behind barefoot running is the theory that we are designed for distance. Lieberman's first big impact on sports science was his research called Endurance running and the evolution of homo³, where he presented the anatomical evidence that humans are the world's best distance runners.

Let's face it, as sprinters, we're pretty lousy. Even the super fast Usain Bolt runs half the speed of most big mammals for about a quarter of the duration! Therefore, if our survival as hunter-gatherers depended on our ability to chase and catch prey, we were pretty much doomed by our lack of speed. Compounding this is that we didn't have projectile weapons until fairly recently, so we had to catch our prey up close. But fortunately, our survival didn't depend on our sprinting ability. It required endurance ability, and that's where we are the champions.

Some of the most important reasons we are so good at endurance relate to thermoregulation. Because we are bipedal the linearity helps us lose heat and absorb less from solar radiation. We are small, we have less hair than animals, and most importantly, we can sweat. This allows us to exercise at fairly high work rates without reaching what is now known to be a critical body temperature that would force fatigue on us. This leads to the theory of persistence hunting, where humans are able to hunt by outrunning the intended prey over hours, rather than seconds. When the animal reaches that critical temperature, it staggers as if drunk, loses motor control and eventually, it just stops completely, lying down for the hunter to make the kill.

This leads to the theory of barefoot running, because Lieberman and others argue that humans are designed for distance — it was essential and the normal state. By extension, wearing shoes is abnormal, and so we must return to what we were intended for — long distance running without shoes. And that's where the evidence comes in!

Shoes and injury

One of the main lines of evidence is actually a lack of evidence. That is, there is not a single study that has shown that shoes reduce the risk of injury. In fact, there is now evidence that the risk of injury is unchanged, maybe even higher in the expensive shoes. Injury rates haven't come down even a little bit since the 1970s, the period which has seen the explosion in the running shoe industry — back in the 70s, the shoes resemble today's minimalist shoes, but about 70% of runners were getting injured, the same rate as today.

There are studies showing that runners who run in the more expensive shoes are more likely to get injured, even when you correct for distance and previous injury history. There is also evidence that prescribing shoes according to the shape of the foot (high arch gets a neutral shoe, flat foot gets a motion-control shoe) does nothing to the risk of injury in a sample of 2,000 in the military.

So all in all, it doesn't look great for shoes. There are a couple of confounders in this line of thinking, which I'll address at the end, but the lack of evidence for shoes doesn't hurt the idea that maybe the foot is best, and we should be discarding the shoes and trusting our feet.

The evidence for barefoot running

What the barefoot theory needs is evidence, and some of that has come from Lieberman, as published in Nature last year³. He looked at barefoot and shod running with the important realisation that familiarity (which may determine "skill") would have an important effect on how their mechanics (and hence impact forces) might be altered. He therefore tested two groups, one which was habitually shod, and another that was accustomed to running barefoot.

The graphs here illustrate the key concepts, and this is really the best evidence for what Lieberman and Davis are saying.

Graph 1

In Graph 1 the top panel shows the force measured during a single ground contact period in a person who is barefoot and heel-striking. The key point on the graph is highlighted — the impact transient, a spike in the force up to around 2.5 times body weight, within the first 50 milliseconds of ground contact. That impact transient represents a sudden increase of force, and the rate at which it is applied (which is basically the slope of the line from contact to that peak) as well as the size of that force, are associated with injury, in particular stress injuries of the tibia (shinbone). The concept of shoes is that they spread that impact out, absorbing some of the force and reducing both the size of the impact transient and also the rate of loading. The bottom panel shows what shoes do.

Forefoot running — the body's cushion

The barefoot condition in someone who is forefoot striking is shown in Graph 2. Here, the impact transient has disappeared — the forefoot landing allows the impact peak to be absorbed by the calf, ankle and Achilles tendon and the result is a smoother profile, and significantly reduced loading rates and forces.

So that’s great news, right? It says that barefoot running is the way to go? In theory.

Graph 2

The problem is that making that transition from wearing shoes to running barefoot involves significant risk, and Lieberman's research shows why. If you’re not careful, then you actually end up increasing the loading rate and the impact force, because you run badly without the protective elastic shoe dissipating that force — as was shown in Graph 1.

Graphs 3 and 4 are the two key graphs.

Graph 3 shows impact force in three conditions. The yellow bar shows the impact force running in shoes, while heel-striking, which is what most people do. In fact, Lieberman found that 100% of people who were accustomed to shoes would land on the heel when they had to run in shoes.

The green bar shows the impact force for people who regularly and “correctly” run barefoot. Lieberman found that in this group about 90% land either on the forefoot or midfoot. As explained, their impact forces are significantly lower.

Graph 3

Those who are not accustomed to running barefoot are the key group, shown in blue. 83% of runners who usually run in shoes would land on their heel even when running barefoot — at least at first. And shown by the blue bar, their impact force is very slightly higher.

But that’s not the major difference. That comes when you look at the impact transient and the initial rate of loading, shown in Graph 4.

This shows that if you run barefoot and are not accustomed to it, you land on the heel, as shown by the blue bar (again, 83% of his normally shod runners). The result is an impact loading rate that is seven times greater than running in shoes with the same landing stance. If the theory is that this impact transient, and the rate of loading, is related to injury risk, this shows that people who are accustomed to shoes who then run barefoot are exposing themselves to higher risk of injury as a result of massively increased loading rates.

That’s the first problem — the purported reduction in injury risk (which is probably real) is dependent on the footstrike technique. If you get it right and land on the forefoot, the impact transient and loading rate are lower (see the green bar).

Graph 4

But if you get that wrong, the consequences may be severe (further research is required on this).

We’re pretty amazing machines, and I can assure you that most people will be able to learn how to run barefoot effectively. That is, with a little practice, they’ll begin to make the adjustments that move them from that high risk group who heel-strike to a more cushioned forefoot strike.

When you take off your shoes and run you’ll find that you’ll be starting to make those adjustments within 50m, because running barefoot on your heels hurts. So we feel the ground, more than we want to at first, and over time, we adjust our mechanics and shift to a forefoot landing. That's why a comfortable majority (90%) of people who are accustomed to running barefoot will land on the forefoot.

That brings us to injury risk number two. The adjustments you make to help cushion the landing have consequences: they transfer the impact forces and loading to the posterior muscles, those muscles at the back of the leg. You land with your toes more pointed away from you, and so your calves are contracted, and catching body weight with every landing. You may reduce the impact forces, but those forces that are left are being applied to very specific muscles. Muscles that may never have been asked to do that kind of work.

The eccentric load on the Achilles tendon and calf muscles is enormous. Your feet and ankles are working much harder, doing what is probably their job, what they are designed for, but they haven’t done it for many years — perhaps a lifetime! The end result is that the strain on the muscle and tendon systems is just enormous, and people break down very quickly.

This is the same outcome you get from introducing things like Pose and Chi running either too quickly, or incorrectly. Your mindset is "land on the forefoot" and that's a pretty tough skill, and challenging demand to cope with for muscles that have for years not been asked to do it!

My own personal experience reflects this. I was regularly running upwards of an hour in shoes, without pain. I went running in Vibrams, and did 30 minutes consisting of 1 min jog, 4 minute walk, repeats. The following three days I could barely walk — my calves, hamstrings and glutes were so tight. It was typical DOMS from eccentric loading that muscle was unaccustomed to.

I know a few people who experienced the same thing. If they overcome the initial stiffness, there is a big risk waiting a week or two down the line, because the constant load on unfamiliar muscles is a huge factor that sees a lot of people get calf or Achilles injuries when trying to run barefoot.

It shows that (a) running in shoes requires next to zero eccentric work in those muscles and (b) when you start running barefoot, you may have to go way back to basics, beyond beginner level, in order to undo what 20 to 50 years of shoes may have caused.

Making the switch — the practical problem

And herein lies the key — the shift to barefoot running is theoretically sound. Lieberman and Davis have a compelling case. But, for some people it may be too big an adjustment to make.

People have different abilities when it comes to learning a skill, and skill is what it will take to shift out of the shoes. It also takes different mechanics, possibly muscle strength, and it is quite conceivable that you'll get a range of responses from every 100 people who make the switch.

Some people will respond brilliantly, and will be able to run long distances barefoot without problems. Some will really battle, and may have to return to beginner level, but they'll learn it. Eventually. Whether they have the mindset or willpower and discipline to do it is another question.

Davis recommends that you start with up to 30 minutes of barefoot walking, followed by progressive introduction of jogging. She started by alternating 1 min jog, 9 minute walk, for 30 minutes. That eventually worked its way to 9 min jog, 1 min walk. Which is all good and well, but if you're running 60-100km per week, the idea of going that far back… not likely.

I do think there are some people who just will not succeed barefoot. Perhaps they have a structural problem somewhere, perhaps 20-40 years of shoes have caused changes that simply cannot be reversed. Perhaps they have muscle weaknesses elsewhere, and barefoot running is not sufficient to overcome those.

High performing runners

The other group that I have to mention is high-performing runners. Not necessarily only the elite, but even those who train for a fast marathon, or Ironman, or even high mileage 10km runners. They are doing 120-200km per week, and a lot of it is fast running. Much faster than persistence hunting would have required — obviously, there is no data, but it's unlikely that humans have ever tried to cover 200km in a week, a lot of it at 7 min/mile or faster, even getting down under 5 minutes/mile for long periods.

There is a real question over barefoot running for people doing this kind of distance running. Some will argue that the reduction in loading rates and impact transients makes it more likely that you can succeed barefoot, especially at high mileage. But there's a confounder here too — muscle fatigue. The third presentation in the symposium showed some really interesting evidence that the loading on the joints and bones was higher as muscles fatigued. This stands to reason, of course — muscle absorbs much of the impact force, and so tired muscle loses that ability, exposing the joints.

So, those who are training for performance may struggle because of a muscle fatigue issue — the muscle is working differently, and harder in certain muscles, when barefoot, and that may be limiting.

Sound theory

On the whole, barefoot running, or at least minimalist shoes, is a sound concept. Lieberman’s theories regarding our ability to run are solid, and I do believe that the days of bulky, motion-control shoes are numbered. I think that barefoot running will be very difficult to implement, if not impossible, for some people and probably doesn’t work in the extremist view that some people are offering for it.

I believe that it may be part of the solution for some of the cases of injury. For some, it may be all of the solution, the solve-all. For others, it will be completely ineffective, and for other still, it will be the cause of their problems.

One of the problems I have in this debate is that those who are advocating barefoot running are basically treating it as medicine — if you have a condition, take a drug, if you have an injury, take barefoot running… The problem is that this is not done with any idea of dosage, "contra-indications" or exclusion criteria, and some might just not be able to do it, which makes one-size fits all advice unhelpful.

The point is that there should never be a single approach to an injury problem. I think there's no doubt that someone who is chronically injured may have their best chance in trying barefoot running. But this cannot come at the expense of a holistic view. I'd put barefoot running forward as part of a solution, something to try, and if you are one who succeeds, then go with it. But if not, then look elsewhere, and don't worry, it's not as simple as some are suggesting.

I would therefore caution barefoot advocates to avoid making the same mistake you accuse the shoe industry of having made for many years. It is said that the shoe industry advocated for many years that shoes were the “answer” — one size fits all (pardon the pun), and that simply putting someone in the right shoe would prevent or cure injury. Now, the barefoot movement is in danger of making the same error — learn from the past and recognise that individuals need individual solutions. So don’t put everyone in a barefoot box.