Running shoe midsole hardness has no effect on running injury rate

It has been well documented that there is a lack of evidence underpinning the most prominent paradigms or models for the prescription of running shoes. That lack of evidence does not mean it is right or wrong, it just means the evidence is lacking as the research has not been properly done in any significant volume. That is why each study on the issues contributes to the knowledge base for a better understanding. For that reason, it was good to see the BJSM just publish this:

Influence of midsole hardness of standard cushioned shoes on running-related injury risk
Daniel Theisen, Laurent Malisoux, Joakim Genin, Nicolas Delattre, Romain Seil1, Axel Urhausen
Br J Sports Med doi:10.1136/bjsports-2013-092613
Background: In this double-blind randomised controlled trial, we tested if leisure-time runners using shoes with less compliant midsoles have a higher running-related injury (RRI) risk.
Method: We provided 247 runners with standard running shoes having either a soft study shoes (soft-SS) or a hard study shoes (hard-SS) midsole and followed them prospectively for 5 months regarding RRI. All information about sports practice and injuries was uploaded on a dedicated internet platform and checked for consistency and completeness. RRI was defined as any first-time pain sustained during or as a result of running practice and impeding normal running activity for at least 1 day. Cox proportional hazards regressions were used to identify RRI risk factors.
Result: The type of study shoes used for running was not associated with RRIs (HR=0.92; 95% CI 0.57 to 1.48). The hard-SS had a 15% greater overall stiffness in the heel region. The two study groups were similar regarding personal and sports participation characteristics, except for years of running experience, which was higher (p<0.05) in the hard-SS group. Global RRI incidence was 12.1 RRI/1000 h of running. No between-group differences were found regarding injury location, type, severity or category. Nevertheless, the adjusted regression model revealed positive associations with RRI risk for body mass index (HR=1.126; 95% CI 1.033 to 1.227), previous injury (HR=1.735; 95% CI 1.037 to 2.902) and mean session intensity (HR=1.396; 95% CI 1.040 to 1.874). Protective factors were previous regular running activity (HR=0.422; 95% CI 0.228 to 0.779) and weekly volume of other sports activities (HR=0.702; 95% CI 0.561 to 0.879).
Conclusions:  Midsole hardness of modern cushioned running shoes does not seem to influence RRI risk

This prospective study simply showed that the hardness of the midsole or ‘cushioning’ did not affect injury risk. Nothing jumps out at me re the methodology and analysis (prospective, good; sample size, good; double blinding, good; outcome measures issues, good; analysis, appropriate).

Of additional interest is the secondary regression analysis that linked injury risk to:

  • higher BMI (shown in other studies)
  • previous injury (all studies seem to be showing that!)
  • mean session intensity (makes sense if you have too many hard sessions)

The factors that were protective were:

  • previous regular running activity (ie the tissues were probably adapted to the loads)
  • weekly volume of other sports activities (does that show the value of cross-training?)

As always, I go where the evidence takes me until convinced otherwise, and that tells there is no need to be concerned that the cushioned running shoes are going to increase the risk for running injury and hopefully that this starts to put and end to the rhetoric and propaganda that they do (that never had any evidence supporting it in the first place).

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One Response to Running shoe midsole hardness has no effect on running injury rate

  1. Steve C September 17, 2013 at 11:01 pm #

    Sample size of 1 here. I can say that for this sample size of 1, I can use a softer shoe like the Skechers Go Run 70+ miles a week without injury. One week at that volume with a hard shoe like the Inov-8 233 leads to injury. Similar shoes other than the firmness.

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