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20

June

Examining a New Study: Pronation Not Linked to Injuries

“So doc, what kind of running shoe should I be in?”

A seemingly straightforward and innocuous question, but one that will take much longer than most people’s attention spans will last. This blog post examines a new study talking about exactly that question and it is grabbing headlines.

If you are short on time and don’t like details, let me sum up the conclusions of this post: When it comes to linking pronation to injuries, it is a highly confusing and gray area. Nobody knows for sure what type of shoe you should be in unless in some cases, muscle/tendon/joint mechanics can be extrapolated from your injured tissue. What we do know for sure, is that it is inaccurate (I’m being polite) for someone to recommend a shoe based off of the shape of your static foot type (high arches, flat foot etc) and even if you have a gait analysis, it is very tenuous to recommend a shoe based on the gait analysis and nothing else. I previously wrote a very detailed article on pronation (patient version found here clinician version found here) and concluded that your shoe choice is a personal one, based on how it feels to you and also based on your injury history with shoes of that type.

The impetus behind this blog is a new study that was just released in the British Journal of Sports medicine called, “Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study” On its surface, this study sounds like the nail in the coffin for the idea that “over-pronating” is the cause on injury. (If you read my other post on pronation you know that I already don’t like the idea of “over-pronation” and injury because it’s way more complicated than that and the research is very, very mixed whether “over-pronation” and injury is a valid and/or reliable association and/or cause.) However, this newest study is…nothing new. This newest study didn’t actually measure pronation during running or walking. Nope, this was a static, non-moving measurement of foot type based on the “foot posture index”. In other words, they had researchers measure the foot arch height of 927 novice runners, put them all in neutral shoes and then followed them for a year to see who got injured. In the end, those runners who were labeled as “pronators” actually had less injuries than “neutrals” (based on their static foot type).

So, of course, the media is going to run with this one (no pun intended). It’s already started with article titles like “Researchers Explode the Myth about Running Shoes, Injuries” and “Corrective Running Shoes are Based on a Myth” but this newest study doesn’t tell us anything new. The idea of basing a shoe off of a runners foot type has been proven incorrect many times before. Below I have listed some studies that clearly have shown that measurements of the foot do not predict how the foot behaves when the person is walking or running:

1. Razeghi M, Batt ME: Foot type classification: a critical review of current methods. Gait and Posture 15: 282, 2002.
2. Hamill J, Bates BT, Knutzen KM, et al: Relationship between selected static and dynamic lower extremity measures. Clinical Biomechanics 4: 217, 1989.
3. McPoil TG, Cornwall MW: The relationship between static lower extremity measures and rearfoot motion in gait. The Journal of Orthopaedic and Sports Physical Therapy 24: 309, 1996.
4. Cashmere T, Smith R, Hunt A: Medial longitudinal arch of the foot: Stationary versus walking measures. Foot and Ankle International 20: 112, 1999.
5. Trimble MH, Bishop MD, Buckley BD, et al: The relationship between clinical measurements of lower extremity posture and tibial translation. Clinical Biomechanics 17: 286, 2002.
6. Dicharry, JM et al., Differences in static and dynamic measures in evaluation of talonavicular mobility in gait. J Orthop Sports Phys Ther. 2009 Aug;39(8):628-34.

This latest study only adds to the pool of evidence verifying that the feet of a moving person do not behave in a way that can be predicted by looking at a non-moving foot. There are too many moving parts that need to be accounted for when running compared to standing. Motions in the pelvis and hip can dictate what happens at the knee, shin and foot. In fact, when this was examined in one study (to my knowledge, the only one to do so) found that when walking or running, control seems to be from the top down, not from the bottom up. In other words, more often than not, your hip and pelvis dictate what your foot will do when walking or running.

So what’s a person to do? There are a few things that need to be considered:

1) If you are happy with your shoes and you are rarely injured even with higher mileage, I think you stick with the shoe type you have been in.

2) If you are injured, you need to take a serious look at your training. I believe most running injuries are from a) ramping up mileage too quickly b) running too fast, too often c) too many miles in general.

3) If you are still getting injured, get a full body gait analysis and look into the credentials of the person looking at your form. Do they know anatomy and mechanics, or did they read “chi running”. No, this statement isn’t based on research reviewed in this paper, but since the research suggests that the mechanics are “top-down”, you need to look into the stability and mobility of the hips, pelvis and core. You may have some hip or pelvic mechanics that need changing.

Obviously we feel that we are well positioned to do the gait analysis.  We have been doing full body gait analysis for 15 years and videotaped around 1,000 injured runners.  We take many post-graduate classes on running injuries and biomechanics.  We both studied kinesiology as our undergraduate programs before chiropractic school.  As this entire post points out, there are many commonly held, but false beliefs regarding running mechanics.  One needs to stay on top of the research.

- Kevin Maggs, ,

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