‘Overpronation’ still continues to be misused and misunderstood all the way from the medical literature to the fan boys in the crankosphere blogosphere. For example, there was this study that got a lot of recent mileage in the mainstream media and the blogosphere that claimed to show that foot pronation was not associated with injury risk. It was intriguing following comments on the study in mainstream media and in social media, especially the parroting of the press release without any critical appraisal. The study actually eliminated the “overpronators” that were probably at high risk from the study then found that “overpronation” was not a risk factor! … go figure! Do you not see the problem with that? What is also all the more intriguing was that there was another study from around the same time that found the exact opposite. Why did the parrots reporting in the media and commenting in social media not mention that study?
Clearly, the data on “overpronation” and risk for injury in runners is mixed, so we need to rely on the more formal systematic reviews and meta-analyses of all the data. The most recent one of those concluded that “overpronation” is just a small risk factor for running injury risk, but it is still statistically significant. As I proposed here, ‘overpronation’ is probably a problem when the magnitude of forces associated with it are high and not a problem when the forces are low. The actual forces will vary significantly from individual to individual and will generally be related to joint axes position variations that affect lever arms and hence the magnitude of those forces involved with ‘overpronation’.
To add to the mix of literature on this topic we now have a new cross-sectional study:
Nahid Divandari, Mahdi Vakili. A Study on the relation between height of medial longitudinal arch and sport injuries in lower limb of professional runners by using Navicular Drop and Arch Index clinical tests. Am Sci 2014;10(3s):50-61]. (ISSN: 1545-1003). http://www.jofamericanscience.org.
I won’t post the abstract as its confusing and does not bear a lot of relationship to what was done in the study. The study recruited 47 runners (somehow they did this randomly!) and measured a number of parameters, including ‘overpronation’, with the navicular drop test. They also did some plantar pressure measurements and other parameters that I won’t report on here. They then compared the navicular drop in the injured and uninjured group. There are a number of red flags in the study, such as the reliability of the measurements used; the retrospective nature of the injury information; some aspects of the study are confusing due to issues with the use of English grammar or terminology issues and my understanding of what they did based on that.
In the context of those issues, what did they find:
So there was statistically significant difference in navicular drop between the healthy and injury groups, but the authors somehow managed to conclude “Despite significant difference of navicular drop variable means in two injured and healthy groups, hypothesis of this paper was not approved and findings showed that there is no relation between sport injuries and medial longitudinal arch height.” I can’t work out from the above data and other data in the paper how they managed to conclude that. The data shows one thing and their conclusion says another!
Also of note is that 36% that had an injury, but we have no idea if this was a current injury (which is massively high) or if it was an injury in the previous 12 months or some other time frame or if they have ever had an injury?
What does this study tell us? Firstly it tells you how not to report a study! Secondly can we accept the data on the differences in navicular drop in the two groups? … I dunno! … maybe I missing something?
As always, I go where the evidence takes me until convinced otherwise and the preponderance of evidence still says “overpronation” is still a small, but statistically significant, risk factor for running injury.