Achilles tendon forces in minimalist and traditional running shoes

This is one of those, not sure what to make of it research projects. This is another undergraduate research project and has all the shortcomings of projects that happen at that level and has not been published in a peer reviewed journal (see the comments on a previous undergraduate project I discussed). This one is from the Worcester Polytechnic Institute in Massachusetts. More and more institutions are placing there undergraduate projects online. Here is the abstract:

Calcaneal Tendon Force Comparison Between Traditional and Minimalist Shoes
Mason D. Andruskiewicz; Jennifer M. Cicchetti; Thomas J. Liguori; James J. McLaughlin
Calcaneal tendon force while jogging was estimated using an inverse dynamics model. Subjects ran in traditional running shoes, minimalist running shoes, and barefoot. Traditional shoes had a heel-toe drop of greater than 10 millimeters, while minimalist shoes were less than five millimeters. Repeatability testing indicated accuracy to within 2.6 times subject body weight. Average maximumestimated calcaneal tendon force was 9.5 ± 2.8 for barefoot trials, 9.9 ± 3.8 for minimalist trials, and 8.2 ± 2.2 for traditional shod trials. Forces were normalized to subject body mass and are unit less. Analysis of variance (ANOVA) indicated no statistical significance between trial types (p>.05, n=14). Results indicate further study of transition from traditional to minimalist shoes.

The results of this study (within all the limitations associated with a project of this nature) are somewhat counter intuitive. They found no differences in the loads going through the Achilles or calcaneal tendon between the three conditions. It could be assumed that the loads should be greater when forefoot striking that is generally associated with barefoot and minimalism, but that is not what they found (ie the higher loads could explain all the pain that occurs in the calf muscles during the transition). However, the goal of the project according to the authors “was to create a reproducible, non-invasive method of testing AT forces while running” and not necessarily testing the differences in the three conditions, but the study report seems muddled and switches between that goal and the testing of the hypothesis of a difference between the conditions. They also appear to have used what looks like a 2D model rather than a more valid 3D model. No data was provided on the subjects and if they were or were not forefoot striking when barefoot and in the minimalist shoes. This was an acute intervention and runners were not habituated to the different conditions. There are many more limitations associated with this project that limits any conclusion being drawn from it. As this is only an undergraduate project where the aim is more to learn the research process, I am more forgiving of the limitations than I would be if this was published in a peer reviewed journal.

However, the big take home message for me, and why I am posting about the study, was browsing the graphs at the end of the report and the massive subject to subject variation in the data….ie if we accept the limitations mentioned above as not being fatal, then there is a large subject specific variation in the Achilles tendon load in response to each of the three conditions.

As always, I go where the evidence takes me until convinced otherwise

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About Craig Payne

University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger, dad. Follow me on Twitter, Facebook and Google+

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