Bone injury and the transition to minimalist running

I have held off somewhat commenting on this research while I watched a number of other blog posts and forum threads on it. As I have stated many times, it is intriguing how so many who are not experienced in the reading, interpretation and critical appraisal of research actually read, interpret and appraise research, especially if it contradicts their world view. This is one more example of that. The response to the research below has been a textbook example of cherry picking, wishful thinking and confirmation bias.

The research in question is this paper:

Foot Bone Marrow Edema after 10-week Transition to Minimalist Running Shoes.
Ridge ST, Johnson AW, Mitchell UH, Hunter I, Robinson E, Rich BS, Brown SD.
Med Sci Sports Exerc. 2013 Feb 22.
Minimalist running shoes are becoming a more popular choice for runners in the past few years. However, there is little conclusive evidence about the advantages or disadvantages of running in these shoes. While performance benefits may exist, injury may also occur from the added stress of running without the benefit of cushioning under the foot. Bone marrow edema can be a manifestation of added stress on the foot. This study measured bone marrow edema in runners’ feet before and after a 10 week period of transitioning from traditional to minimalist running shoes.
Thirty-six experienced, recreational runners underwent MRIs before and after a 10 week period. Seventeen subjects were in the control group (ran in their traditional shoes only for 10 weeks), while the other 19 were in the experimental group (gradually transitioned to VibramFiveFinger running shoes over 10 weeks). The severity of the bone marrow edema was scored on a range of 0-4 (0 = no bone marrow edema, 3 = edema in more than 50% of the length of the bone). A score of 4 represented a stress fracture.
Pre-training MRI scores were not statistically different between the groups. The post-training MRI scores showed that more subjects in the Vibram group (10 of 19) showed increases in bone marrow edema in at least one bone after the 10 weeks of running than in the control group (p = .009).
Runners interested in transitioning to minimalist running shoes, such as Vibram FiveFingers should transition very slowly and gradually in order to avoid potential stress injury in the foot.

This was a pretty good study with a couple of minor issues. Essentially, what they showed was that in the group that transitioned to the Vibram FiveFingers there was more bone stress injury detected on MRI, yet somehow many have interpreted this study as a fatally and significantly flawed study because for no other reason than they do want to believe the results! (ie, the fallacy of wishful thinking).

My comments:

  • When I look at the inclusion criteria; subject selection; sample size; validity and reliability of the baseline and outcome measures; the blinding of assessors; and the statistical analysis, I see no issues that are flawed. There may be an issue with how they managed the analysis in the context of the dropouts from the study, but this is really minor, was allowed for in the sample size calculation and does not invalidate the study and is not out of the ordinary like that you would get in other studies of this nature (yet some have cherry picked this point to claim the study is not valid and at the same time accept other studies with similar dropout rates that support their world view!). I am also a little uncomfortable with the nature of the unconventional randomization process, but will let it pass (ie picking group allocation out of a hat vs computer randomization).
  • One of the main criticisms that the critics of this study are using is that the transition in the group going to the minimalist Vibram FiveFingers was too short at 10 weeks, and therefore this invalidates the study. When doing research of this nature, all researchers sometimes have to make a judgement call when it comes to the protocols. There is nothing wrong with that as long as there is some rationale or logic to the decision the researchers made regarding the protocol and it can answer the research question. In this case, the decision on the 10 weeks was based on advice on the Vibram FiveFingers website! How can that 10 weeks be not enough if they were following the advice of the manufacturer of the minimalist shoes that they were using in the study? The researchers can easily justify their decision for the 10 week transition¹. I have even seen some claims that this study deliberately set out to injure people by using the 10 week transition protocol. These clowns might as well turn up in court on behalf of the plaintiffs in the class action and state that Vibram Five Fingers are deliberately injuring people, as they were following Vibrams protocol!
  • A lot of comments got made about the ‘experimental design’ being flawed. I see no problem with the experimental design. It answers perfectly the research question that was asked. Those making the ‘flawed’ claims have no idea about ‘experimental design’ and were really talking about something that was a totally different research question which this project was not about.
  • There has been some criticism directed at the compliance that those who were in the Vibram FiveFingers group with the transition protocol, but I do not see that as an issue. I see it as a good thing as it makes the study more reflective of what happens in the real world and the real compliance that happens with the transition protocols.
  • Some have called the 36 subjects as a small study! This is just showing an ignorance of sample size calculations, statistical power and significance and effect sizes. Paradoxically, none of the Chi Running websites considered 9 subjects a small sample size in a study on Chi Running! Those that criticize the study based on the sample size are happy to accept studies with smaller sample sizes if the results supports their views. See the irony and hypocrisy?
  • There certainly is a lot of confusion on the web as to exactly what bone marrow edema actually is. There is a good summary here for those who still don’t get it.

This study clearly showed that there is increased bone stress injury in those who transition to Vibram FiveFingers following the protocol that was advised on the Vibram website². Cherry picking and grasping at straws on really minor issues does not invalidate the study. Those that are cherry picking and grasping at straws over these really minor issues are also the ones that do not put studies that support their world view under the same level of scrutiny. Why is that? This study does not auger well for Vibram in their class action defense.

For anyone wanting the 1 minute superficial summary of this research, here is one of the researchers talking about it:

As always, I go where the evidence takes me until convinced otherwise, and I see nothing in the methods and results of any significance that invalidates this study. All research should be critically appraised, but at the same time all research should be held to the same standards and not different standards because it does or does not support your world view.

¹Having said that, 10 weeks is probably too short in general and for many people they probably should be expecting more time than that. I often advise people to take up to a year. If you can do it quicker, then fine. Despite my age and body weight, I was able to do it in less than a couple of months! It is going to be very individual.

²Vibram FiveFingers have since removed that advice.

Ridge ST, Johnson AW, Mitchell UH, Hunter I, Robinson E, Rich BS, & Brown SD (2013). Foot Bone Marrow Edema after 10-week Transition to Minimalist Running Shoes. Medicine and science in sports and exercise PMID: 23439417

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5 Responses to Bone injury and the transition to minimalist running

  1. Alien Booth March 16, 2013 at 5:38 am #

    It was good to read this take on the study. I had read about the study on other sites and was certainly under the impression from them that this was a really bad study. It appears I was being biased by the commentary on those sites from people who after reading the above clearly did not know what they were talking about.

  2. Christian March 22, 2013 at 2:53 pm #

    I too have noticed the lengths that they have gone to on some barefoot sites to demolish this study. It is good to see a balanced and sensible approach to the research.

  3. Craig March 22, 2013 at 3:00 pm #

    Thanks. Its very telling isn’t it! It was part of the reason that I started this blog. I never cease to be amazed at the lengths some go to to discredit, “demolish”, deconstruct research that they do not like the results of or conflicts with their world view. There is nothing wrong with critical appraisal of research, but what is wrong is that you never see them put the same level of analysis to research that they like the results of….. don’t figure!

    You can’t have it both ways and are exposing themselves to ridicule that they do this.

  4. Craig April 1, 2013 at 4:04 am #

    I have just had a read of this:
    The final nail in the coffin for the antivaccine rallying cry “Too many too soon”?

    The parallels between the above and how the vaccine causes autism cranks also grasp at irrelevant straws and totally fail to understand research and science are uncanny, but we see it so many times in so many fields.

  5. Thor Vandehei July 2, 2013 at 1:00 am #

    First, let me say I thought this was overall an excellent study.

    But really, what is the big surprise by their results? Nothing, really, in my opinion.

    When runner’s attempt to make the transition to “minimalist” shoes they shows signs of damage to the underlying musculoskeletal systems in the foot, albeit mostly asymptomatically. Is this not what happens when one goes to the gym and works out vigorously? The muscle and bones are stressed, they recover, and recover stronger and we built strength and endurance. If we overdo it, too much, too fast, we injure ourselves. What’s the surprise?

    One serious confounding factor in making conclusions here is the lack of footstrike observation in the any of the runners (“traditionally” shod or in VFF). If we don’t measure footstrike, then we’ll never tease out whether those transient GRFs actually matter or not. Plenty of people who wear VFF heelstrike, and some “traditionally” shod runners forefoot strike, and, as you know, there is a whole continuum in between. Perhaps the one calcaneous stress fracture observed in this study was a result of heelstriking in VFF, but we’ll never know as the footstrike patterns were not reported.

    BTW, how many complete novices could transition from zero to 10 miles per week injury free in 10 weeks? Not many. Running without shoes, or in “minimalist” shoes really is like starting over from scratch, I think you’ve said as much elsewhere in your blog, and I wholeheartedly agree.

    However, I think a more “fair” comparison, and interesting in its own right, would be to see the results of a similar study, conducted as this one was, but which looked at novice runners, with no prior running experience, grouped into “traditional” and “minimalist” shoes, who undergo an initial (10 week?) training session, but with running form (footstrike, cadence, pace, etc.) observed periodically throughout the training to supplement running logs, MRI foot scans, etc. As Trappeniers (2003) found (cited in the paper), novice runners (presumably “traditionally” shod as the date of the paper is 2003) also experienced significant bone marrow edema after only 1 week of beginning a running program!

    Perhaps this is a minor grumble on my part, but I find it mildly disturbing that this paper (and I’ve seen others) do not cite which of their subjects smoke and how often. As I’m sure you know, this has been shown time and time again to predict future injuries, though it does seem unlikely to have biased the data.


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