Barefoot running and shoes Q & A Part 4

17 Mar 2010 Posted by
Thanks to everyone for the discussion around the previous post.  I’ve really enjoyed the debate.  I must make the point that any views here are obviously opinion.  Why?  Because there’s no conclusive evidence that putting a runner who has run in shoes for 20 years into either lightweight shoes, Vibrams, or barefoot, will reduce their risk of injury.  Until someone produces that prospective, well-controlled study over a long period, anyone’s “answer” in this debate is going to be opinion.  Yes, there is a lot of evidence against shoes, but that’s because science seeks to disprove the current hypothesis, and little has been done to show up problems with barefoot running – it’s too soon.

And what we’ve seen so far is the running shoe equivalent of the “shark attack” phenomenon, where the occurrence of an event is greatly inflated by a reporting bias (shark attacks are exceedingly rare, yet we are all terrified of them, because the media coverage given to them is disproportionately high).  Similarly, I really do believe that there is bias in barefoot running reporting, because the people who come forth with their stories are those who have succeeded.  No one has yet documented the failure rate – people who have abandoned the barefoot campaign.  And yes, these people are likely to have failed because they made an error in increasing their volume or intensity too rapidly, but equally, those who get injured in shoes can be accused of the same thing (van Gent, 2007 [1]).

As this series progresses, I’ll move towards stating what I would recommend as as a practical approach to barefoot running, based on the evidence like that discussed yesterday, and which will be described more today, as well my own experience and work with runners.  But the best part of being able to discuss this topic is to share in those opinions – as is typical though, when people disagree with them, they tend to take out the “you’re losing objectivity” club.

Today’s post delves a little more into the shoe evidence, looking particularly at the “intelligence” of the body with and without shoes.  Then I end off with some discussion around the whole argument that our ancestors and the Tarahumara Indians run barefoot, and therefore so should we.

Again, in isolation, this post will be strong theoretical evidence for barefoot running, which I hope most have gathered is a recurring theme.  I’m actually very positive about barefoot running and the role it can play in every runner’s training and development.  I’m just trying to maintain some balance, lest the movement become, in the words of a respected colleague, “a stimulus plan for physical therapists and podiatrists”!  And believe me, they’ve made a good few new patients as a result of over-zealous implementation!  Here goes, with questions 10 to 13.

10. There is research (Robbins and Gouw 1991) that says that running with cushioned shoes leads to the fact that the perceived impact on the body is lower than the actual impact (or: our body is fooled by the cushioning). How do you interpret this research?

This body of research is extremely interesting. It’s been borne out by a number of studies which have looked at impact, soft tissue vibration and muscle activation. Benno Nigg has proposed “muscle-tuning” where the degree of muscle activation, especially pre-activation (which is the muscle activity immediately before the foot strikes the ground) is adjusted depending on the impact conditions in order to defend the soft tissue vibration (Boyer & Nigg, 2007 [2]). In other words, the body is “smart” enough to anticipate the impact conditions, and whether the cushioning exists and then it regulates impact and vibration by adjusting muscle activation. The simple analogy is that if you stand up on your office chair and jump off it, you can land extremely hard if you just let gravity work on your ‘dead weight’, or you can cushion your landing through anticipation of the impact and the correct muscle activity. That’s what the body is doing in mid-flight, which is quite remarkable.

Whether the perception of impact is important or not, I’m not convinced either way. Let’s say that you run in a highly cushioned shoe, and you perceive the impact to be much lower than it actually is. So what?  Some would say this is a favourable outcome, because any time you can perceive less impact, it’s good. What Nigg is proposing with muscle-tuning concept is that the forces and the vibration of the soft tissue are being regulated. So perception is not reality, in this case. And the impact forces may not be higher – studies seem to disagree on this particular aspect. So I certainly believe that the perception is altered, but I don’t necessarily agree that the body is being “fooled” by this – the perception is being fooled, yes, but the brain and the muscles may be managing it quite appropriately!

What is significant, and this is a strong argument for why bulky shoes do have a negative effect, is that the ability to “feel or sense” the ground may be altered by shoes. Sensory information from the foot, which tells the brain of underfoot conditions, surface hardness, slopes, objects, is certainly altered by shoes, and this may affect the timing of muscle activity, as well as the degree, particularly towards the end of races, when fatigue is a factor.

Incidentally, the same scientists did a really interesting study a few years later, in 1997, where they made people step onto a material that was the same as is used in the midsole of running shoes (Robbins & Waked, 1997 [3]). They did this a number of times, but the difference was that they were either told that the material was a state-of-the-art cushion, with all the latest technology to minimize injury (they even drew graphs and made up fake endorsements from athletes), or they were warned that it was the same as the material used in cheap shoes, responsible for many injuries. This is the WARNING trial shown in the graph below. Effectively, they were evaluating how belief about cushioning affected impact.

deceptive-ad

It turned out that when subjects thought they were landing on the soft, high-tech material (Deceptive trial), the impact forces were actually HIGHER than in the Warning trial when they expected the cheap and ineffective material. And barefoot had the lowest impact forces of all. The other amazing finding, as is shown in the graph above, is that in the barefoot and cheap material trials, the impact forces get lower and lower as the subjects repeat the step, which shows a learning effect that is not present in the ‘Deceptive’ trial where subjects thought they were landing on a soft material. So this is remarkable – it shows how an expectation of impact can actually alter impact, and again, it supports what Benno Nigg and others are saying about anticipation of impact, with the ability to adjust muscle activity to defend some other variable.

This is why it’s possible to run barefoot – the body is a remarkable machine, able to make in-flight adjustments to provide the optimal landing, and this is a strong argument for why being barefoot might give some advantages. At the very least, when people stare in wide-eyed horror at those who run in either light-weight shoes, or Vibrams, or bare-foot, because “you’re running without essential cushioning”, they’re reacting to a misperception – the body can provide cushioning.  And there is evidence for this – from Daniel Lieberman’s latest study, from Nature.  We looked at this in a little more detail recently, but the graph below shows one of many interesting findings.

Lieberman

Here, the impact forces are shown for three groups:  First, on the far left, are runners who normally wear shoes, running barefoot. In the middle, runners who are wearing shoes, and on the far right in the shaded box, habitually barefoot runners, who strike forefoot.  Clearly, the impact force is reduced in the forefoot strikers when barefoot.

However, there’s a catch to this whole argument.  The danger is that in order to provide this cushioning, muscles are working harder.  In my answers to an earlier question (Q 4, in Part 2 of the series), we looked at some of the changes in running patterns when barefoot.  The knee is more flexed, the ankle more plantar-flexed, and the landing point more at the forefoot.  These changes are responsible for helping with the cushioning, but mean greater load on the calves (particularly the soleus muscle) and Achilles tendon, which rises substantially, and now you can see why this is happening – it cushions the landing very effectively. When this cushioning response is used, those muscles and tendons are taking enormous strain, and if they are not adapted or eased in, they break down. So again, we have a situation where theoretically, there’s a lot to be said for barefoot/minimal cushioning, because it allows the body to do what it does best. But there’s a real danger there too, which has to be acknowledged, and then managed very carefully.

11. One of the claims of barefoot runners is that most of the modern shoes (which have serious heel cushioning) take away essential sensory information while the barefoot runners’ body uses the rich sensory information the foot provides.

Nike Free’s, Vibram Five Fingers also work in the sense that they do not ‘disconnect’ the sensory input of the foot. Is that a valid argument? If so, what are the benefits?

Yes, and I think this is a strong argument for barefoot running. Whether the sensory “barrier” still exists in minimalist shoes, I’m not sure. The advocates for barefoot running say that the shoes, no matter how similar to barefoot running, do affect sensory feedback. My experience is also that they do, but not nearly as much as a normal cushioned or stability shoe. The Vibrams in particular feel remarkably similar to barefoot running – studies suggest that the mechanics are the same, and the sensory feedback is as near to barefoot as is possible – it’ll never be the same, because there’s a 4 mm barrier between the foot and the ground. But it’s close, and this may have beneficial effects. Again, that’s never been proven – it is a theoretical position only, but it does offer a potential upside to barefoot/minimal shoe running.

12. Another claim is that modern shoes are considered to act like corsets: they give support but also make the muscles lazy and therefore weaker. Is there any proof that this statement is correct?

The study we looked at yesterday, by D’Aout, showed how chronic shoe use changes the morphology and biomechanical function of the foot.  So it’s certainly true that way.  Also, if you go out and run barefoot, even for a short time, you’ll discover muscles in the foot and calf that you had long ago forgotten you had! The stiffness and some of the muscle sensations you feel when you run barefoot is completely unexpected – this suggests that running in shoes involves very little work from those muscles. So from that point of view, it’s easy to say that, yes, running in shoes does reduce the work done by certain muscles of the foot.

However, to extend that position and say that this increases the risk of injury while in shoes is a stretch for which I don’t believe there is proof yet.  What this evidence does is explain why it’s so difficult to run barefoot when you’ve been in shoes for a long time, but I don’t think it translates the other way.  Similarly, if one runs barefoot and these muscles are developed, will it reduce the risk of injury when you then run in shoes? It sounds reasonable, certainly, but it could equally be true that when you wear shoes, those muscles do not need to work and therefore can be weaker.

The analogy is that you can become wastefully strong, and we tend to balk at the idea that we can “afford to be weak”, but it all comes back to what is required in order to do a specific task – a marathon runner, for example, may not have a strong upper body, but training the arms and improving their strength by 50% doesn’t produce a faster runner. So is it possible that shoes have created a situation where the work required of the foot is reduced, and this is acceptable, provided the runner continues to be in shoes? Again, no one has really provided proof to answer these questions.

However, I believe that barefoot running offers the potential to help improve foot strength, which may reduce injury risk, if it is managed correctly. A number of coaches, for example, will have athletes to a small amount of running barefoot, and I think that is reasonable, even recommendable, because it helps with the strength of these muscles. Overdo the barefoot running early and you’re headed for disaster, however, as I said previously.

13. Then there is the anthropological view: we ran for millions of years on our bare feet; our bodies are not made for walking on running on shoes which have a heightened heel (ranging from high heels to air in sneakers). Do you agree?

I’ve heard this position, and while I can see the merit to the thinking, I think it’s probably the weakest argument for why we should run barefoot, for a couple of reasons:

First, the conditions under which we run today could not be more different than they were millions of years ago. The hardness of running surfaces has changed, the terrain is completely different, and even the way we run is different – a structured 60 minute training is vastly different to a 8 hour migration or hunt that may involve walking, climbing, crawling and resting.

Second, we are different. I’m no anthropologist, but I’d like to see a profile of what the individuals looked like in these “endurance runner” communities. Were some of them 100kg or heavier?  Did they all have a natural inclination for running? In a village of say 100 people, did 100 of them run successfully in order to hunt? Or was the hunting and locomotion done by 20 out of the 100, with the others doing other things that perhaps did not involve such a great deal of endurance work – perhaps some were fishermen, while others hunted? Just as today, if you took 100 people at your running club, you might find 5 great runners, 25 good runners, 50 average runners and 20 non-runners, there’s no guarantee that our ancestors all run well (please note that I’m illustrating a principle here, so please don’t attack the numbers…). Unless I’m missing something? So perhaps it’s possible we are comparing those hunters, the “elite runners” of those communities, to our struggling runners, when we should be saying that guys like Ryan Hall or Dathan Ritzenheim – they run just as well as any ancestor did?

And then perhaps most crucially of all, and this is the biggest flaw in this particular argument, there is very little in our lifestyle that is similar to what it was or is in these communities! For example, 2010 man is sitting at a desk for 8 or 9 hours a day, driving a car 80% of the time of locomotion, and spending maybe one hour a day doing exercise. Even as children, we are less active, playing less outside and more on computer games. Many years ago, hunter-gatherer humans were playing, physically active for 12 hours a day and thus developing the strength that perhaps allowed them to run for enormous distances without the same injuries. And yes, they happened to be barefoot! But there are about a hundred things they also did differently. Yet for some reason, we’ve looked at this picture and said “The big difference between us and them is that they were barefoot”. We’ve spotted the wrong difference – the reason they did what they did is because they were stronger in the supporting muscles as a result of their lifestyle. We are weak, unprepared for hours of impact while running, and shoes just happen to be a new addition while this has happened.

Bottom line, don’t blame the shoes for the injuries, look at the training and degree of physical readiness for running, because 9 hours of desk work and years of inactivity produce weakness and inflexibility that is found out by 60 to 70 km a week of training.

Part 5 next

So that’s Part 4 done. Apologies for a long post today, but hopefully it stimulates the same kind of discussion!  Tomorrow may be the last post, certainly it will be the last of the interview, and then I may manage to squeeze in a post at the end to wrap up.  So join us tomorrow!

Ross

References

  1. R.N. van Gent, D. Siem, M. van Middelkoop, A.G. van Os, S.M.A. Bierma-Zeinstra, and B.W. Koes, “Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review.”, British journal of sports medicine, 2007. http://www.ncbi.nlm.nih.gov/pubmed/17473005
  2. K.A. Boyer, and B.M. Nigg, “Changes in muscle activity in response to different impact forces affect soft tissue compartment mechanical properties.”, Journal of biomechanical engineering, 2007. http://www.ncbi.nlm.nih.gov/pubmed/17655481
  3. S. Robbins, and E. Waked, “Hazard of deceptive advertising of athletic footwear.”, British journal of sports medicine, 1997. http://www.ncbi.nlm.nih.gov/pubmed/9429006