Like the running economy and footwear type issue, I have been meaning to write for a while an article that summarizes the studies on the differences in injury rates between heel strikers and non-heel strikers; but before I got to doing it another two studies appear, so its worth writing about those. To date we have 4 studies (now 6) that have looked at this:
- Daoud et al (2012) was a retrospective review of 52 almost elite level track runners (that are not close to being representative of typical runners) which found the injury rate in the heel strike group was almost double the forefoot striking group. This study got an extraordinary amount of press coverage (and Vivobarefoot cherry picked it to produce a poster).
- Kleindienst (2003) was a retrospective review of 471 typical runners that found no difference between rearfoot and forefoot strikers concerning the frequency of injury.
- Walther (2005) was a retrospective review of 1203 runners that also found no difference in incidence of injury between rearfoot and forefoot strikers in the rate of injury.
- Goss & Gross (2012) was a self-selected, self reported web based survey that reported data from 1605 runners that no one is giving much weight too (except this loon) due to the self-selected nature of the study design. They did report that traditionally shod runners were 3.4 times more likely to get an injury that a minimalist runner.
The first new study is by Grier et al and is being presented at next weeks American College of Sports Medicine meeting, was also a retrospective study design. They looked at 1332 soldiers of which 17% were wearing minimalist running shoes. They reported that in the abstract that “When controlling for personal characteristics, physical fitness, and a history of prior injury, there was no difference in injury risk in the previous 12 months between soldiers wearing minimalist runners shoes compared to soldiers wearing traditional running shoes“. Obviously we are assuming that those wearing minimalist shoes were more likely to be a non-heel striker.
The other new study is a paper that is also to be presented at next weeks American College of Sports Medicine meeting, Warr et al assessed 342 soldiers and after assessing their foot strike pattern, 13% were classified as non-heel strikers. They found no differences between the injury rates and days lost from injury between the heel strikers and non-heel strikers.
On any hierarchy of the strength of evidence for ranking the importance of research results, all 6 of the above studies rank in the middle or closer to the bottom, mostly due to the retrospective nature of the designs of the studies. Some of them have other issues that affect their interpretation and applicability. For example, the almost elite level of the Daoud et al participants and the self-selected self-reported participants used in the Goss & Gross study – I single these two out as they are the ones most often mentioned in the cherry picking crankosphere blogosphere. For some reason you hardly ever see the Kleindiest and Walther studies mentioned, despite them having very large sample sizes of typical runners; but are also limited due to the retrospective nature of the design. The new larger studies by both Warr et al and Grier et al confirm the results of the Kleindiest and Walther studies.
To me, the evidence is looking increasingly clear that there is probably no difference in injury rates between heel and and non-heel strikers despite all the rhetoric and propaganda. As I suggested here, there are probably different injuries with different foot strike patterns (which the Walther (2005) study reported).
POSTSCRIPT 2: Differences in injury rates between…
As always, I go where the evidence takes me until convinced otherwise.