Review of Lieberman et al’s (2010) paper in Nature on Barefoot Running

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Since starting this blog I have tried to cover every relevant piece of research when its published as well as summarize some topics in the context of what the evidence is saying. I have missed a few and still do have a bit of a backlog of recent ones. It all comes down to allocating time to do it (I do have a life, a family and have to make a living). Having said that, there are a lot of bits of research that were published prior to me starting this blog that still continue to be misused, misinterpreted, misunderstood and misquoted. So I am now going to regularly go over some older ones and still try to keep on top of the recent ones.

What spurred this was the systematic reviews on barefoot running (reviewed here, here and here) that all clearly show that there is no generic benefits to it. The systematic reviews were not done by me, I only commented on them. The reviews were all done by people from many different backgrounds and all published in a number of different journals. A systematic review is a formal structured review of all the available and good quality scientific evidence. They all have reached the same conclusion. A number of emails and comments I have received were asking things like (paraphrased): “Why won’t you accept the evidence of  Lieberman et al’s (2010) paper in Nature that barefoot running is better?”. I should know better than to respond to questions like that, but I often do with comments like “What evidence?” and “Did they actually show that?”, as that is not what they showed. The conversations usually go downhill from there with all the usual trope of logical fallacies getting thrown at me and the Dunning–Kruger effect is on full display. Lets take a closer look at the study, here is the abstract:

Foot strike patterns and collision forces in habitually barefoot versus shod runners
Daniel E. Lieberman, Madhusudhan Venkadesan, William A. Werbel, Adam I. Daoud, Susan D’Andrea, Irene S. Davis, Robert Ojiambo Mang’Eni & Yannis Pitsiladis
Nature 463, 531-535 (28 January 2010)
Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.

As this study made the cover of the issue of Nature that it appeared in and was accompanied by a press release, it went viral in the mainstream media as well as in the crankosphere blogosphere. It also coincided with the publication of Born to Run by Chris McDougal the previous year. The rest is history. More often than not the study is quoted as evidence that barefoot running is better at reducing injuries despite it not even being a study on injuries and despite all the systematic reviews of all the evidence concluding the opposite.This is also despite Lieberman himself posting a disclaimer on his website that this is not what they showed:

Please note that we present no data on how people should run, whether shoes cause some injuries, or whether barefoot running causes other kinds of injuries.

So what did the study actually show?

I had a problem with the study right from the very first sentence:

Running can be most injurious at the moment the foot collides with the ground.

If you are going to make such an emphatic statement in the academic literature, there should be at least a citation to support the claim. There was not one. As I keep saying the evidence for impact loads actually causing injury in runners is far from compelling, so the whole premise that the paper is based on (ie impact reduction) may be flawed.

The study basically looked at three groups of runners: habitually shod runners from the USA; Kenyan runners who grew up barefoot but now run in shoes; and USA runners who grew up shod but now run barefoot or in minimalist footwear. They then looked at the kinetic and kinematic data between the three groups.

Simplified, they found:

  • shod runners who grew up wearing shoes mostly rearfoot strike when running in shoes and barefoot
  • runners who grew up barefoot or switched to barefoot mostly forefoot strike when running
  • forefoot strikers did not have the heel impact transient that the rearfoot strikers have

But:

  • When it came to the statistical analysis they eliminated the African group from the data, yet how often is this study cited as comparing African “barefoot runners” (who were actually wearing shoes) to USA shod runners?
  • I won’t comment on the sample size, as I have no issues with it; except to say all the fan boys are going to have to reject this study as there was 8 in each of the USA groups – they have rejected a  number of other studies that have larger sample sizes as they think the sample was too small!
  • When you look at the two groups of USA runners (shod and barefoot/minimalist) the mean ages were 19.1 yrs (shod) and 38.3 yrs (barefoot). Can you not see a problem with that?

That is all they showed, yet look at all the citations that the study has as showing a lot more than that or quoted as showing something that they did not show.

What the study didn’t show:

  • it did not show that barefoot running was better; in the context of the limitations above, it only showed it was different; yet look at what this study has been cited as showing!
  • it did not investigate or report where the loads went up in the barefoot running group to get the reduced impact forces. Forces do not go away, the loads get moved to other structures. They did not report on that nor even consider the potential injury risk to those structures that it was moved to. Other studies do report that.

As always, I go where the evidence takes me until convinced otherwise, and in all honestly this study does not really tell us much at all. What it does really show is how gullible the mainstream media and crankosphere blogosphere are at interpreting and reporting science.

The authors should be congratulated for getting published in Nature which has an impact factor of 38. I would not mind getting published there.

Lieberman DE, Venkadesan M, Werbel WA, Daoud AI, D’Andrea S, Davis IS, Mang’eni RO, & Pitsiladis Y (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 463 (7280), 531-5 PMID: 20111000

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