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Wednesday, March 17, 2010

Barefoot running and shoes Part 4

Barefoot running and shoes - the Q & A Part 4

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).

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). 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). 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.



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.


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 antropological 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

22 Comments:

Adam said...

Hey guys,

First, just finished you book and loved it. Keep writing this blog and anything else and I'll add it to my list.

My question on this whole barefoot/footstrike debate is, "Could it be 'best' to be able to modulate your running style during a run?" It may be mental trickery, but when I'm tired mid-run I try to identify muscles that I am not engaging and use them. Sometimes this changes my posture or footstrike, but it also seems to allow me to run longer. Perhaps I am mentally duplicating conditions that would occur naturally were I to run on trails/hills/rocks instead of my normal paved routes. I would be curious to hear your thoughts.

Tuck said...

"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."

This is an odd perspective. "It's too soon?"

People have been running barefoot or in minimalist shoes for most of our history. Unlike many other health issues, the impact of barefoot running on health has been well understood. "Put your shoes on or you'll step on something!"

Being barefoot has become a health issue before, most notably in the case of hookworm in the Southern United States, so it's not that no one's looked at the problem. And given that we had a President who was famed for running barefoot, it's not that that issue hasn't come up before.

The US Army has been dealing with shoe design and feet for over 100 years, only in the last few decades has the "running-related injury" become an issue of concern. In 1915, when they first looked into the issue, they made no mention of any running-related injuries (or any injuries) except for those caused by shoes. This study is, as far as I can find, the only broad look at the issue of shoes, injury, and athletic performance. They did find that many types of common injuries caused by wearing badly-fitted shoes can be corrected by wearing properly designed and fitted shoes, which is a very important finding. And, most importantly, they found that the injury rate in marching can be significantly reduced with properly designed and fitted shoes. Today, for whatever the reason, running-related injuries are the number one injury reported in basic training.

Interestingly, the form suggested by the Army for moving troops quickly across land, the double-time march, is identical to POSE.

The Roman army similarly marched for centuries wearing minimalist footwear (leather sandals), including forced marching (running). I'm not aware of any accounts of systematic injury similar to the modern era (the injury rates cited for modern runners would have put the Roman army, or any other army that travelled on its feet, out of commission entirely).

I'm a student of history, so I'm biased. Not all questions are new. ;)

Gene said...

A wonderful series, even if you are mostly saying the same thing over and over from different angles.

I would add a point to your very good answer to Q13. In my Q1 comments against the oft-toted notion of "natural," I spoke to introduction of footware in human evolution, at least by Mesopotamia, 3500 or so years ago (effectively social evolution, since little time has elapsed biologically speaking since then). A question that arises from the shift to footware is, Did our ancestors, especially settled ones, know something not only about safety, health and productive development re footware, but also about body mechanics? And if so, did this knowledge extend to activities that involved running and quick walking, short and long distances? Or, to put it from the other end of our history, to what degree have our modern views and debates about footware and foot biomechanics in sports and everyday life been unduly influenced by the nature and needs of industrial mass production and marketing in a "market-driven" (capitalist) era, as opposed to the needs of our bodies?

Gene said...

Tuck, I didn't see your post until after submitting my comment. The quibble I have with your comment about the Roman army and their use of sandals is that 1) males conscripted, enslaved or volunteered into armies in those days were already far more physically active by social standing and lifestyle than modern ones; 2) the technological level wasn't such to design and mass produce more substantial footware, so the sample is biased, so to speak; and 3) the Roman government couldn't have afforded to supply and resupply mass armies with shoes, anyway. Thus, it's hard to draw too much from their empirical experience when looking at modern populations, which I think is Ross' point. Their thinking about foot covering and movement, to the extent its known, is that available?

Anonymous said...

I wanted to provide some comments regarding your points dismissing the argument that humans have always been barefoot, and therefore shoes can be damaging. I don’t think this argument is properly understood.

Obviously – at least in warm weather – humans are born with the capacity to do just about everything barefoot. There are millions of people living in Asia, the Americas, and Africa that go barefoot from cradle to grave and prove this conclusively. Some studies even suggest they have healthier feet, but I wouldn’t argue that point.

One point no one has addressed is the possibility that our running features (Achilles tendon, nochal ligament, etc.) could be vestigial or phylogenetic traits. For example, perhaps our expensive and intricate running adaptations evolved to serve humans hundreds of thousands of years ago, but recently selective pressure to insure the health of these traits was relaxed. After all, we’ve changed a lot just in the last 50,000 years. We’ve become much less robust and have essentially domesticated ourselves (thinner sculls, smaller brains, probably much more rule-following, etc.). With the selective pressure for running genes relaxed due to technology as simple as the bow and arrow and even atlatl, deleterious genes could have been allowed to multiply and become commonplace.

I also think most people misrepresent hunter-gatherer societies. We weren’t made to go barefoot for 30 years than die. In fact, hunter gatherers can be extremely long-lived, at least once they survive their extremely high murder rates. People often confuse the lifestyle characteristics of the Pleistocene with the dawn of agriculture, when we lost 5 inches of height, all of our teeth, much of our longevity and picked up some nasty crowd diseases by switching to a diet of grains (vs. our “natural diet” of meat, vegetables, and fruits). Lastly, hunter gatherers don’t always have the hard lifestyle (again, a confusion with the dawn of agriculture) as you portray. Many often work as little as 4 hours a day and have more leisure time than us. They can be quite lazy and idle.

It’s one thing to say shoes don’t cause injuries. It’s quite another thing to say we NEED shoes. We obviously don’t. Shoes do indeed make our American and European feet weak, but we all have the potential – at least at birth – to go barefoot. (btw, it’s obvious, but it’s important to note that we’re tropical apes and never evolved the complex adaptations of other species, like dogs for example, to keep our feet warm in freezing weather. So out of the sun belt we do, in fact, NEED shoes).

Even if we’re no longer runners, our feet are well equipped at birth to spend 80 years barefoot. Further, this evolutionary design does have implications for how shoes affect our health. I would elaborate, but I just don’t know enough about shoes and how they affect feet. Finally, the natural world our feet are evolved for isn’t any softer than ours. Remember, city streets are for beginning barefooters. If you want some really hard barefooting go into the woods and plains where your ancestors came from.

thanks for the article

Anonymous said...

Then it should be better to run in worn out shoes, which is closer to barefoot. Injuries should decrease as a function of increasing age of your shoes.

Ross Tucker and Jonathan Dugas said...

Hi Tuck

I think I must clarify what I'm saying there. I agree that there are no new questions, but you have to bear in mind that in terms of the research on injuries, nobody has really evaluated the long-term impact of being barefoot. They have looked at shoes - all these studies (and those yesterday) take the prevailing hypothesis, and then challenge it. That is the way it's always done. So guys are looking at shoes, which are supposedly protective, and saying "can we disprove that hypothesis?"

And slowly, that's starting to happen. However, it's too soon for the reverse to be done. No one has yet looked at barefoot, long-term, and said "can we prove the failures of barefoot running?" It's too soon for that, because the general approach is always to challenge the prevailing hypothesis. And while the barefoot movement is not new, it's still "new" in terms of research on science. at some point in the future, evidence will begin to surface looking at barefoot with the same "negative approach" that shoes have been looked at, which is the point I'm making there in the statement you've quoted above!

Ciao
Ross

Steven Sashen said...

Of course what I'm about to report is anecdotal and from a data sample of one -- me.

When I took off my shoes and ran barefoot, the feedback I got from the sensations of my feet on the road did a few things:

1) Got me so interested in the sensations, that I ran further and longer than I ever have before

2) Pointed out to me what no coach ever saw -- that I was overstriding when I sprinted

3) Taught me what NOT overstriding felt like and, therefore, changed my stride when I sprint (I've gotten faster)

I get the same experience with huaraches running sandals, but with the added bonus of some protection from the elements (unlike my experience with VFFs which, I think, provide too much structure and reduce the ground feel too much).

And, as a reminder (self-promotion alert), you can get complete (and free) instructions about making running sandals at http://www.InvisibleShoe.com (where you can also get huaraches kits and custom-made sandals)

Simon Martin said...

Thanks Ross: a couple of points.

First, it would have to be my pal Steven - a sprinter - to bring up the one point nobody's highlighted and I was anout to: speed.

As runners we are not, most of the time, focused on what will enable us to run for the longest amount of time or distance without injury. Instead we are usually focused on what will enable us to run faster.

Is there any evidence that running barefoot enables us to run faster? "All" (sweeping generalisation alert) the champion runners who started their careers barefoot - for example Olympic marathon champion Abebe Bikila and 5k world record holder and world x-country champion Zola Budd - switched to shoes. Budd because of injury.

Second - addressing sensory feedback. Check out the new "Hubbles" here - http://www.hokaoneone.com/
These are like running with two foam pillows strapped to your feet. But they are a *neutral* shoe. And before you dismiss them as a joke - they were developed by mountain runners to let them run down the sides of mountains - faster. They had used minimalstic and specialist trail shoes but were fed up getting their feet bruised by rocks giving them *too much* sensory feedback.

Thirdly, and related to the concept behind the Hubbles: I don't think the problem with modern running shoes is "that most of the modern shoes (which have serious heel cushioning) take away essential sensory information" as you say in 11...

... no, it's that the vast majority of them (just check the adverts) are specifically designed to *force* (OK they tend to use words like "encourage" or "enhance") a heel strike, followed by a straight roll from heel to toe. Because someone somewhere has decided this is the "natural" footstrike for everybody, everywhere, at every speed and distance, and on every type of terrain.

On top of that, they also embedded with all sorts of other "protective" features such as widgets to "control" pronation - which is a natural and necessary motion of the foot - to some theoretical normal degree. Modern shoes are deliberately designed to interfere with the natural motion of the foot - and only running barefoot over forgiving terrain can reveal what that is.

And finally, I tend to agree with physical therapist extraordinaire - and former word marathon champion - Mark Plaatjes, who, based on his own running experience and the evidence of injured barefooters he sees in his clinic, that there are some people for whom barefoot running is just not on.

Craig T said...

Hi Gents
I enjoy reading your blogs- the closest thing to a balanced, unbiased view on barefoot running I have seen.
I am a Podiatrist and have treated multitudes of runners including international level athletes from different backgrounds (Kenyan and Caucasian).
One thing that you haven't mentioned is that modern society involves us running on unnatural surfaces a disproportionatlely large amount of time. By this I mean that we are on flat, completely regular surfaces. This means that an individuals foot is being put into the same postion with every step... repetitive same load on the same tissues... increase injury risk?
Some people will have natural alignment, range of motion and strength for which this will pose no problem... others will not. Shoes orthoses etc are one mechanism do deal with this- there are other mechanisms also.
For what it is worth- I believe I see more problems with a shoe which is too soft, rather than too firm. I have also seen many problems from shoes which have too great a difference between support and cushion sections in a dual density 'motion control' shoe- some call this 'too controlling' but I do not thing this is a good desciption- perhaps 'not balanced'?.
As a Podiatrist I see the negative effect of poor footwear choice and wearing one pair of running shoes for too long. I have also the seen the positive effect of correcting this with a better shoe choice. You cannot dismiss the importance of shoes (I know you guys haven't...)
As for barefoot running- some people can, some can't. My feeling is that the positive effects are likely due to correction of technique deficiencies... probably overstriding. I would recommend it potentially as part of a training program, introduced gradually, and on natural- variable- terrain.

aluchko said...

Anonymous @ 11:21 PM

Well put, I have to say I broadly agree with your post on our evolutionary history.

Farhad N Kapadia said...

Hi Ross,

I fully agree with your point that we are making educated guesses regarding injury & await long term data. Till such time as this is available, what are your views on using barefoot training techniques on one or two days a week.

I also think the overall discussion and comments have not adequately separated out regular runners from those starting out. Would like to point out from two aspects of the Nature paper that the data is really not applicable to middle age people who are planning to start running.
Quoting the Lieberman paper.
Methods: For all adults, criteria for inclusion in the study included a minimum of 20 km per week of distance running and no history of significant injury during the previous six months.

Table 1: Relatively small number of participants: n = 63 & relatively young adult population with subgroup mean ages of 19, 23 & 38 years.

Colenso said...

I feel I need to make some basic observations about some of the underlying mechanics here:

1. When standing still, a person experiences an upward force, exerted on the soles of his or her feet, equal in magnitude and opposite in direction to his or weight, measured in newtons. (NB weight is a force, in the SI system measured in newtons; body mass is a mass, in the SI system measured in kilogrammes).

So, for example, a 70 kg male runner has a weight of roughly 700 newtons (roughly 10N/kg (9.81N/kg to 3sf)) acting vertically downwards through his centre of gravity. When standing still, the ground pushes up on him, with a force of 700 newtons acting vertically upwards through his centre of gravity.

Hence, the net vertical force acting on the runner at that moment is zero (700 newtons down acting on his centre of gravity, less 700 newtons up acting on his centre of gravity (forces are vectors, so directions as well as magnitudes must always be specified)).

2. When the runner steps on to a force plate, the force registered by the plate ranges from zero (before and after the runner has stepped) to the maximum registered instantaneous force.

When he is standing still, this maximal upthrust is a force equal and opposite to the runner's weight. If we talk about the specific force (force per unit of mass) the specific force is about 10N/kg (9.81N/kg to 3sf). When he steps on to the force plate the instantaneous maximal upthrust (per unit of mass) of the plate is 12N/kg while stepping on to the plate(see Figure 1, "Deceptive", here in Part 4). When he runs, the maximum instantaneous upthrust is about 2.4 x 9.81 N/kg, as shown on page 2 of the web pages at http://www.barefootrunning.fas.harvard.edu/2FootStrikes&RunningShoes.html based on the recent study by Lieberman et al.

3. It's important to note, however, that even when merely standing still the runner must experience an upthrust from the ground on his feet equal and opposite to his body weight. (He must do, otherwise he will accelerate downwards, as when the ground gives way beneath him!)

4. So, one needs to be aware that the NET upthrust in Fig 1 here (that is over and above the upthrust experienced when merely standing) would appear to range from ((10.7N/kg - 9.8N/kg)/9.8N/kg (initial barefoot) to ((12N/kg - 9.8N/kg)/9.8N/kg (deceptive) ie from roughly 9% increase (initial barefoot) to a 22% increase (deceptive) over and above the upthrust permanently experienced when merely standing still.

5. Likewise, on the Lieberman website, the NET increase over and above the maximum upthrust on the soles when simply standing is actually 1.4 times the body weight (ie 2.4 - 1) (at least in the example shown on page 2).

Anonymous said...

I know this is a running site, but,
What do you think of Barefoot weight lifting?

I hear what you are saying about the village and not everyone runs fast,
some thing in strength / weight lifting / Bodybuilding. Some people are hard gainers. Some put on mass very easy.

Also, about heel lift, can you review the literature and compare bf people and people who wear heels (1 inch at least) and see who has more hip, knee, and ankle problems? Arthritis? Need for hip and knee replacements?

One more thing, have you considered getting a stand up desk.
Donald Rumsfield popularized them when he was DOD. They look neat.
Like to know your thoughts.

Simon Martin said...

Tuck said...
"Interestingly, the form suggested by the Army for moving troops quickly across land, the double-time march, is identical to POSE."

Not hardly. The only similarity is a high cadence and need for a shorter stride.

"The Roman army similarly marched for centuries wearing minimalist footwear (leather sandals)..."

Roman military sandals were not "minimalistic" - have you ever seen a pair? They were complex constructions held together with metal rivets and studded with hobnails. Have a look at this reproduction: http://alexisphoenix.org/romansandals.php, plus of course it *should* go without saying that they were NOT designed for running, but for marching while carrying a pack weight of around 30kg.

The British Army has been in business for a while and is the only force I know of that has ever attempted to produce a running/training shoe. The results are here:
http://www.runtheplanet.com/shoes/selection/armyshoes.asp
They haven't caught on.

Tim Butterfield said...

I commented yesterday about becoming a runner after more than twenty years of inactivity and being overweight. The issue of raised heels was also important in my change. Prior to wearing Vibrams, I wore normal, regular shoes all the time, Florsheim for dress up and New Balance the rest of the time. I also walked with a cane due to back issues. After discovering a report by Dr. Rossi, (Why Shoes Make "Normal" Gait Impossible, I switched from normal footware to minimal (flat) footwear, the Vibrams. It was only after removing the raised heel that my back improved sufficiently to allow me to begin exercising and running (and put away the cane). Though I am but one example, I think Dr. Rossi had it right. Raised heels do have a negative effect.

As for the hardness of running surface, I think a hard smooth surface is likely better than a hard pointed surface like mountain trails. In nature, unless you are in a flood plain with thick silt deposits, no surface is uniformly soft. There are always rocks, roots, nuts, bones, and other things buried in the grass. As illustrated in question ten, the predictable modern surface more easily allows our body to adapt to it even if it is a hard surface.

Anonymous said...

Two points:

1) 1st world runners run in shoes. 3rd world runners would run in shoes if the economics permitted. (My opinion of course.) Of ist world barefooters I read about, they only turned to barefoot because of injuries the doctors/podiatrists could not heal. They tried barefooting and it worked. Not for reducing racing times, but for general overall fitness and pleasure. It may only be 30% of those who tried barefooting that it worked or it may be less or more. But that is still more people still running than would be otherwise. I believe McDougal only wrote his book "Born to Run" because his feet hurt while running and the final medical advice was to quit running. He found that advice wrong for him.

2) You mention barefoot runners plantar extend their feet prior to touchdown (strike). I disagree. Maybe the newbies do, but those of us who have been around the block a few times so to speak don't. The foot is dorsal flexed along with bent knees at the landing which is directly underneath our body mass. The plantar flexor touchdown runners are probably over reaching and are not real barefooters but those who train barefoot on soft surfaces like grass and rubberized tracks. Also, if one were to take a side view movie of my feet landing it would for all appearances look as if the landing is flat footed or on the heel. But the weight of the landing is - if only a "frog hair" - on the balls of the feet. So unless one were using a sensor pad to monitor the landing one would see the runner heel striking. Those runners up on the balls of their feet by plantar flexing are definitely going to spend a lot of time hurting in their calcaneal tendons and soleus regions.

Great discourse by the way.

Charles Hickenlooper

Tuck said...

"Simon Martin said...
"Tuck said...
"Interestingly, the form suggested by the Army for moving troops quickly across land, the double-time march, is identical to POSE."

"Not hardly. The only similarity is a high cadence and need for a shorter stride."

Double-time march is done at 180 ppm, so is Pose. Both specify a forefoot landing, shortened stride, neither allows for a heel-strike. Both have lower injury rates that running in sneakers. Watch videos of both, or look at the Army's own analysis of double-time marching. The forms are identical.

Pose is derived from barefoot running (according to Romanov, if you run barefoot, you're doing Pose). If you do a double-time march, you're doing a run that is handed down unchanged from a time prior to modern footwear.

Ross Tucker and Jonathan Dugas said...

Hi Tuck

I would contend a number of statements regarding Pose.

For one thing, no one has ever shown a lower incidence of injury with Pose. That's just the marketing material speaking. If anything, it's higher in practice because people cannot cognitively implement the method without injury. A few will succeed, most will get injured. In the study I was involved in at UCT, the data they never wanted to publish was that injury rates were up near 80%. All ankle or calf. And that was after 2 weeks of 2 hour a day one-on-one supervision by Romanov himself. I shudder to think what would happen with a manual and a DVD for an hour a day to most people.

Second, the link between the Roman army and Pose is tenuous at best. Pose doesn't specify a forefoot landing, actually - Romanov taught midfoot and if challenged, would often say that you should not land on the forefoot. Yet certain sections of their material did, so that was a mixed message.

Pose, packaged in the form it was, may be one of the biggest 'stimulus packages' for physical therapists that we've seen. Unfortunately, this data is never tracked.

Ross

Simon Martin said...

Thanks for weighing in, Ross.
To pick up more on Tuck's comments:

Pose does not specify a cadence. When I trained with Dr Romanov he did not specify a cadence, just wanted it to be quicker.

Pose is anything BUT military and it is left for the individual to find their own cadence. (You will find recommendations from Pose coaches, as from all running coaches, to emulate the cadence of elites, which is usually a minimum of 180.)

Secondly, I'm not sure how you are comparing quick time MARCHING with Pose RUNNING?? How is possible to look at marching and running and conclude they are indentical? Hmm.

Lastly, what Tuck may not be aware of is that two essential ingredients of Pose are a forward lean (to the point of falling) and an ACTIVE lift/pull up of the foot under the hip. I can't see any forward lean in Army marching; and few people will be able to spot an active hamstring pull-up as demo'd by Pose runners. Similarly, It would be nigh on impossible to work out if that is what Army quick-time marchers are doing just from looking at videos, but I doubt they are.

I second Ross's comments on the injury potential of Pose and the "hidden" data.

said...

Hi Ross,

As a phd student in biomechanics and lots of interest in exercise physiology, I think you do a great job overviewing a lot of the potential pros/cons in the barefoot issue.

I would like to comment on a few thoughts from a more mechanical perspective.

1) In Lieberman's paper, while the impact force was higher in heelstrike shod runners than FFS barefoot runners, the rate of loading was not significantly different, as I recall. While there is much debate as to what induces injury, I believe the rate of impact force development is one of the main contenders. It is interesting that this result is not discussed much by the authors or elsewhere. Perhaps Skeleton might comment?

2) A rubber sole has different frictional properties than human skin. The ability to regulate angular momentum is key in maintain balance, and generating forces at certain angles may be beneficial from a VO2 consumption standpoint. I would guess that humans would not land with a large horizontal velocity difference between the barefoot and ground, whereas with a rubber sole, a larger velocity difference may be allowed.

While barefoot running allows more tactile sensation, it may also reduce the range of options in running mechanics. Perhaps those options aren't good, but I think this must be considered. Sprinters of course wear thin shoes but also have cleats to generate more frictional forces.

3) Surface matters. As you mentioned in one of the posts, people will change mechanics based on surface. Running barefoot on concrete will likely induce different mechanics that running on grass. And there may be differences in mechanical efficiency (power out / VO2 in) between barefoot / shod across surfaces.

4) This has probably been mentioned, but simply the shape of modern running shoes limits the ability to perform FFS. With a raised heel, the ability to use te ankle as a spring with a FFS pattern is reduce with a loss of range of motion about the ankle. Everyone is getting so caught up with barefoot running, but perhaps the first step is to simply reduce the heel and induce more mid and fore-foot strike running that way.

Cheers

Joe

SSB said...

I like this series on BF running, I'm going to pass it on to a couple friends considering it.

One thing I told them is that they've been running in shoes for 35 years....or nearly 35 years, so their stride is adapted to running in shoes. And changing how you run is hard (believe me, I've tried to fix my form many times), so if you are used to running one way, take away a big part of it, and you're probably still going to run with a lot of similar motions (even though I know you won't heel strike as much), but there's enough that it can cause problems/injuries if you don't work into it slowly.

In the past 3 years I've gone from a serious heel striker in fully cushioned motion control shoes (that i ran in for 20 years based on my over pronation), to a forefoot/midsole runner in neutral light weight trainers and a good 50 miles a week, and my achilles injuries/calf/piriformis problems are gone. But when I tried to run 1/2 mile barefoot (easy pace on a track after a 15 minute run to the track) the other day then put shoes back on to finish the workout, my achilles was screaming at me by the end of the run.