I think we have known for a while that the data supporting a prescribing of running shoes based on the “pronation” paradigm is either lacking evidence or not supported, not withstanding the largely superficial understanding of the concepts and the superficial interpretation of the various studies and their implications. Some of the studies on this that pointed to the problems were done by Joseph Knapik and colleges on military populations. Now they have done a meta-analysis of their studies, pooling the data into one larger cohort:
Injury Reduction Effectiveness of Prescribing Running Shoes on the Basis of Foot Arch Height: Summary of Military Investigations
Joseph J. Knapik, ScD, Daniel W. Trone, PhD, Juste Tchandja, MPH, Bruce H. Jones, MD
J Orthop Sports Phys Ther, 22 August 2014.
Study Design Secondary analysis of 3 randomized controlled trials.
Objective Analysis of studies that examined whether or not prescribing running shoes on the basis of foot arch height influenced injury risk during military basic training.
Background Prior to 2009, running magazines and running shoe companies suggested that imprints of the bottom of the feet (plantar shape) could be used as an indication of foot arch height and that this could be used to select individually appropriate types of running shoes.
Methods Similar studies were conducted in United States Army (n=2168 men, 951 women), Air Force (n=1955 men, 718 women), and Marine Corps (n=840 men, 571 women) basic training. After foot examinations, recruits were randomized to either an experimental or control group. The experimental group selected or was assigned motion control, stability, or cushioned shoes matching plantar shapes judged to represent low, medium, or high foot arches, respectively. The control group received a stability shoe regardless of plantar shape. Injuries during basic training were determined from outpatient medical records.
Results Meta-analyses that pooled results of the 3 investigations showed little difference between the experimental and control groups in the injury rate (injuries/1000 person-days) for either men (summary rate ratio (SRR)=0.97, 95% confidence interval (95%CI)=0.88-1.06) or women (SRR=0.97, 95%CI=0.85-1.08). When injury rates for specific types of running shoes were compared, there were no differences.
Conclusion Selecting running shoes based on arch height had little influence on injury risk in military basic training.
This was not a new study but a reanalysis of data from previously collected and published studies. The pooling of data for a meta-analysis has the strength of the larger sample size so stronger conclusions can be made. The three studies included in the analysis used similar methods. Participants in the experimental groups where given a motion control shoe, a stability shoe or a cushioning shoes based on the plantar shape of the arch of the foot. The control groups were all just given a stability shoe. They found no differences in the rates of injury between the two groups.
Based on this data the authors concluded that: “That selecting or assigning running shoes on the basis of foot arch type did not reduce injuries and military basic training compared to assigning a stability shoe regardless of plantar shape. ” I concur, that is what the meta-analysis of the studies showed, but that was all it showed. In other words the blanket recommendation of prescribing based on that plantar foot shape is not supported, but that is also based on the assumption that the static plantar foot shape is representative of dynamic foot function (which it is either not or is very weakly correlated). It is this extrapolation from the findings that is somewhat problematic.
There are so many questions and so few answers. There are different causes of higher or lower arches (the studies did not control for them). Different arch height may be different risk factors for different injuries (the studies did not control for them). Different design features in different shoes will affect the different causes of higher or lower arches differently (the studies did not control for them).
The other problem with using arch height as the parameter to measure “pronation” is problematic because “pronation” has several components to it. You can have a high arch but still have an everted calcaneus. Is that a “pronated” foot or not? In the above study it would have been it would have not been classified as a “pronated” foot. You can also have a very low arched foot with the vertical calcaneus; is that a “pronated” foot or not? So you can see where I’m going with this. Those familiar with the concepts of planal dominance will understand this in more depth. Superficially, if you think arch height represents pronation then the study can be interpreted one way. If you think arch height is one component of what we consider “pronation” then the study can be interpreted another way. I guess all all depends what blinkers you are wearing (ie your preconceived biases). I have previously discussed all the nonsense that goes on around the interpretation of “overpronation” and some of the issues with that and the study needs to be interpreted in that context.
Some of this was encapsulated by this insightful comment here by Eric Fuller (which I will cut n paste here so as not to plagiarize him and claim credit for the seed that he planted in my head!):
It’s nice that tested the axiom that shoes should be based on arch height. The frustrating part for me is that there is no theory behind the idea. Why would one shoe be better for a low arched foot. They looked at stability, motion control, etc. without any theory on why one one shoe would be better for a high arch or a low arch.
If you wanted to do research on shoes and injury you should look at the design changes in the shoe and how they alter mechanics and then compare that to how those design changes might alter stress on specific anatomical structures. It should not just be was there an injury, but was there a specific injury.
Most anti pronation shoes are designed to shift the center under the heel more medially. This will reduce the pronation moment from the ground. This will theoretcially reduce the incidence of posterior tibial tendonitis. Theory also predicts that feet with a medially deviated STJ axis will be more likely to have posterior tibial tendon dysfunction. So, I want to see the study where people with medially deviated STJ axes are put in anti pronation shoes and those with a lateral STJ axis are not put in anti pronation shoes and then look at the incidence of selected specific injuries. Grouping all injuries might help with statistics, but theory would predict that specific injuries would be addressed with certain modifications.
People reading the conclusion of that article should not think that all methods for selecting a specific shoe modification will not prevent injuries. As was correctly stated in the paper arch height vs shoes did not prevent injury. Other methods might.
“Overpronation” has many causes; some of which can theoretically be influenced by running shoe design features and it has other causes that can not be influenced by running shoe design parameters. If the above study only included those causes of “overpronation” that can be potentially influenced by running shoe design parameters, then they may well have got a different result. Also, as alluded to in Eric’s comment above, if they only looked at the data on specific injuries, such as posterior tibial tendinitis, in which a shifting of the center of pressure more medially by a ‘motion controlling’ shoe, which hypothetically will decrease the load on that tendon. Such design features would not affect the load in other types of injuries. Can you see where this discussion is going and why the superficial interpretation of the results of studies such as the above can lead of in the wrong direction?
Also to throw into this mix is what I keep saying about running injuries are that they are caused by too much load in the tissues beyond what the current state of the tissues can take. The main biomechanical reason for a high load in the tissues is higher joint moments. That has nothing to do with arch height or “overpronation”; it has everything to do with variations in joint axes positions and the effects that they have on loads (eg supination resistance). We should be more concerned about what the different design features in running shoes can do to alter the application of force relative to the joint axis and the influence that has on tissue loads.
As always: I go where the evidence takes me until convinced otherwise … and based on this study the generic advice to prescribe running shoes based on the static arch print is not supported. There are so many other factors to consider.
POSTSCRIPT: A red flag has since been raised about these studies by one of the participants in them. See this report from Paul Ingraham.
Knapik, J., Trone, D., Tchandja, J., & Jones, B. (2014). Injury Reduction Effectiveness of Prescribing Running Shoes on the Basis of Foot Arch Height: Summary of Military Investigations Journal of Orthopaedic & Sports Physical Therapy, 1-25 DOI: 10.2519/jospt.2014.5342