Is the drop of a running shoe associated with injury risk?

I previously blogged about the evidence on the use of zero drop vs a higher drop of running shoes and concluded that there is no evidence for one drop over another. Judging by the comments that the post received the ‘fan boys’ did not like that conclusion, responding with the usual rhetoric and propaganda and trope of logical fallacies. I could see nothing wrong with that conclusion as there was no evidence for any one particular drop over another. My own personal belief based on my understanding of the evidence and in my own experiences and my discussion with runners and running shoe retailers is that each individual runner does seem to have a drop ‘sweet spot’. There just seems to be a certain amount of drop that suits each individual runner that is usually found by trial and error. In other words its subject specific. For those not up to speed on terminology, ‘drop’ refers to the difference in the height of the shoe between the heel and forefoot. Typically a traditional running shoe has around 10mm. The ‘fan boys’ consider anything other than zero mm to be evil.

Having said that, things on the evidence front have just taken a turn:

Influence of the Heel-to-Toe Drop of Standard Cushioned Running Shoes on Injury Risk in Leisure-Time Runners
A Randomized Controlled Trial With 6-Month Follow-up

Laurent Malsioux, PhD, Nicolas Chambon, PhD, Axel Urhausen, Prof., MD and Daniel Theisen, PhD
Am J Sports Med August 8, 2016
Background: Modern running shoes are available in a wide range of heel-to-toe drops (ie, the height difference between the forward and rear parts of the inside of the shoe). While shoe drop has been shown to influence strike pattern, its effect on injury risk has never been investigated. Therefore, the reasons for such variety in this parameter are unclear.
Purpose: The first aim of this study was to determine whether the drop of standard cushioned running shoes influences running injury risk. The secondary aim was to investigate whether recent running regularity modifies the relationship between shoe drop and injury risk.
Study Design: Randomized controlled trial; Level of evidence, 1.
Methods: Leisure-time runners (N = 553) were observed for 6 months after having received a pair of shoes with a heel-to-toe drop of 10 mm (D10), 6 mm (D6), or 0 mm (D0). All participants reported their running activities and injuries (time-loss definition, at least 1 day) in an electronic system. Cox regression analyses were used to compare injury risk between the 3 groups based on hazard rate ratios (HRs) and their 95% CIs. A stratified analysis was conducted to evaluate the effect of shoe drop in occasional runners ( Results: The overall injury risk was not different among the participants who had received the D6 (HR, 1.30; 95% CI, 0.86-1.98) or D0 (HR, 1.17; 95% CI, 0.76-1.80) versions compared with the D10 shoes. After stratification according to running regularity, low-drop shoes (D6 and D0) were found to be associated with a lower injury risk in occasional runners (HR, 0.48; 95% CI, 0.23-0.98), whereas these shoes were associated with a higher injury risk in regular runners (HR, 1.67; 95% CI, 1.07-2.62).
Conclusion: Overall, injury risk was not modified by the drop of standard cushioned running shoes. However, low-drop shoes could be more hazardous for regular runners, while these shoes seem to be preferable for occasional runners to limit injury risk.

Nothing in the methods and analysis jumps out at me as being problematic and as this is a prospective randomized trial, then this is a high level of evidence. And, most importantly, the write up complied with the CONSORT statement.

Their conclusions were clear and supported by the data:
Overall, there were no differences in the injury rate between the different drops.
Low drop shoes increase the injury risk for regular runners (>6 months running).
Low drop shoes decreased the injury risk for occasional runners

 

As always, I go where the evidence takes me until convinced otherwise ….and zero drop is not a safe as its made out to be; but i still think there is a ‘drop’ sweet spot that is subject specific.

Malisoux, L., Chambon, N., Urhausen, A., & Theisen, D. (2016). Influence of the Heel-to-Toe Drop of Standard Cushioned Running Shoes on Injury Risk in Leisure-Time Runners: A Randomized Controlled Trial With 6-Month Follow-up The American Journal of Sports Medicine DOI: 10.1177/0363546516654690

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8 Responses to Is the drop of a running shoe associated with injury risk?

  1. blaise August 10, 2016 at 1:38 am #

    good study in general
    My comments on your thought :
    1- “… each individual runner does seem to have a drop ‘sweet spot’.” : No. the only reason why some are not tolerate 0drop is the habit during young age. Nobody healthy need drop.
    2. “Typically a traditional running shoe has around 10mm.” : it was 16 some years ago… why? No idea… (and the industry and his ‘scientific’ don’t know too 🙂

    • eric johnson August 19, 2016 at 9:46 pm #

      How do we know that 4mm drop, 6mm drop or 10mm drop aren’t better for performance or injury resistance than 0mm for some people – even if they grew up in zero drop shoes? I agree it sounds reasonable but is there any science to support the claim?

      Also, it’s changing the subject by saying there wouldn’t be a sweet spot if people all grew up in 0 drop shoes. We have to deal with the populations that are alive today and the fact is that many did grow up with those shoes.

  2. Duncan Arnold August 11, 2016 at 10:07 am #

    Was there an adaptation period for the regular runners? If not then no surprise there may be an association with increased injuries.

    • Craig Payne August 11, 2016 at 12:37 pm #

      Irrelevant. It was prospectively randomized; so “adaptation” or not was the same in each group. Equal numbers of previously experience with 0 drop in each group as well.

  3. eric johnson August 19, 2016 at 9:49 pm #

    Does anyone want to speculate why there could be an injury difference for low and high drop shoes between regular and occasional runners?

  4. Heather Stacey September 11, 2016 at 2:40 pm #

    I speculate that runners who have difficulty in 0 drop shoes lack gastroc/soleus flexibility and
    /or needed ROM at the ankle.

  5. BCR September 15, 2016 at 7:38 pm #

    Craig – wow! After reading the previous blog and comments (many of which appear to believe that the rejection of a hypothesis on statistical grounds carries the obligation to proposal a counter-hypothesis, or that all such counter-hypotheses must be correct) you couldn’t have wished for a more opportune study. 🙂 Did they read your blog?

    Yet I fear that the results may be misinterpreted. So (assuming the validity of the study), it clearly concludes that:

    1. There is a statistically significant increase associated risk of injury for runners using 0mm or 6mm shoes compared with 10mm shoes that do greater than or equal to 6 months of weekly practice over the last 12 months.
    2. There is a statistically significant decrease associated risk of injury for runners using 0mm or 6mm shoes compared with 10mm shoes that do less than 6 months of weekly practice over the last 12 months.

    That’s it.

    What it does not say is (yet I suspect that some marketing sleight of hand will do this at some point):

    1. Anything at all about >10mm shoes (which is a shame). In other words, some may erroneously say “well I’m a regular runner, and if 6mm is riskier than 10mm, 13mm must be even better”! That is not a valid conclusion scientifically (because the study doesn’t say that) nor logically, because if we take that to it’s extreme, 1000mm are even better. 🙂 (There probably is a point at which the benefits tail off, and who knows? Just maybe it is 10mm.)

    2. 0mm and 6mm cause the increased risk of injury. As we know: “correlation does not imply causation”. Yet, how long before someone says “0mm shoes are more likely to cause injury in regular runners”. 🙂

    3. All regular runners will get an injury with 0mm shoes.

    Now, if I were the authors of the study, I’d be applying for a research grant to do a wider study and include a > 10mm heel drop. 🙂

  6. Brandon November 5, 2016 at 3:04 am #

    I left a reply on your previous thread, but there are benefits to low drop minimalist shoes for those that need to augment their strike pattern to alter loads (in my case, compartment syndrome). If an individual knows their own needs, there is science to aid them in making a good choice.

    Loads to areas of the leg muscles in different footwear and footstrike patterns:

    https://www.ncbi.nlm.nih.gov/pubmed/?term=footwear+FFS+RFS+minimal

    Low drop (minimalist) and hip kinematics (possible options for female runners that sustain knee injuries and pain):

    https://www.ncbi.nlm.nih.gov/pubmed/25207927

    Running economy:

    https://www.ncbi.nlm.nih.gov/pubmed/27328725

    Forefoot running and compartment syndrome:

    https://www.ncbi.nlm.nih.gov/pubmed/22427621

    Biomechanical effects of footwear on footstrike pattern:

    https://www.ncbi.nlm.nih.gov/pubmed/25983575

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