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Forefoot runners have fewer injuries, but causality unclear

PainSci » bibliography » Daoud et al 2012
Tags: barefoot, counter-intuitive, classics, foot, leg, limbs, pain problems, running, exercise, self-treatment, treatment

One article on PainSci cites Daoud 2012: Does barefoot running prevent injuries?

PainSci commentary on Daoud 2012: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This important retrospective study of Harvard runners found that forefoot (barefoot or minimally shod) runners had half the repetitive strain injuries — emotionally compelling evidence that this style of running is useful. If true, as author Dr. Dan Lieberman pointed out, “it’s the biggest effect ever shown on running injury.”

However, the abstract of the paper declares that it “does not test the causal basis” for these results — and indeed it cannot. This is retrospective research — examining old data, gathered without controlled conditions. Restrospective studies, especially small ones, cannot in principle reveal causation, and are notoriously prone to pollution with confounding factors. Nevertheless, Lieberman seems to believe the data is persuasive — he presents these new results enthusiastically and perhaps too uncritically in an otherwise excellent and fascinating talk for, Brains Plus Brawn.

I agree it is emotionally compelling evidence. However, I am also uncomfortably aware of how shockingly, seductively easy it is to be fooled by an appealing correlation like this. There are other possible reasons why forefoot striking Harvard runners might have lower injury rates! It is not necessarily running in bare feet or barely-there running shoes. Many alleged causal relationships in the history of science, just as “persuasive” as this one, turned out to be wrong. So, I note these results with interest, and I admit for the first time that maybe — just maybe — this barefoot running fad could turn out to be important.

But I must still reserve judgement until cause is confirmed by good quality research.

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

PURPOSE: This retrospective study tests if runners who habitually forefoot strike have different rates of injury than runners who habitually rearfoot strike.

METHODS: We measured the strike characteristics of middle- and long-distance runners from a collegiate cross-country team and quantified their history of injury, including the incidence and rate of specific injuries, the severity of each injury, and the rate of mild, moderate, and severe injuries per mile run.

RESULTS: Of the 52 runners studied, 36 (69%) primarily used a rearfoot strike and 16 (31%) primarily used a forefoot strike. Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike. Traumatic injury rates were not significantly different between the two groups. A generalized linear model showed that strike type, sex, race distance, and average miles per week each correlate significantly (P < 0.01) with repetitive injury rates.

CONCLUSIONS: Competitive cross-country runners on a college team incur high injury rates, but runners who habitually rearfoot strike have significantly higher rates of repetitive stress injury than those who mostly forefoot strike. This study does not test the causal bases for this general difference. One hypothesis, which requires further research, is that the absence of a marked impact peak in the ground reaction force during a forefoot strike compared with a rearfoot strike may contribute to lower rates of injuries in habitual forefoot strikers.

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