November 2016

Out on a limb: Strike pattern revisited

1Limb-JordanaBy Jordana Bieze Foster, Editor

The concept of foot-strike pattern during running—something rarely discussed a decade ago, even in research circles—is now pervasive among runners as well as biomechanics experts and lower extremity clinicians. But that’s not necessarily a good thing.

To be sure, discussing the risks of running-related injuries in terms of foot-strike pattern is preferable to discussing those risks in terms of barefoot vs shod running. While many barefoot runners will swear that giving up footwear forever is the only true path to health and happiness, researchers have demonstrated that many of the impact-related benefits of barefoot running are related to the fact that runners are far less likely to use a heel-strike pattern while barefoot than while shod. And midfoot- or forefoot-strike patterns aren’t exclusive to barefoot runners; they can be observed in plenty of shod runners too.

Shifting the discussion from barefoot-or-bust to the relative benefits of different foot-strike patterns has acknowledged some of the complexity involved and has made runners feel they have more options for reducing their injury risk. There’s just one problem: It turns out that foot-strike pattern can be pretty difficult to determine. Research suggests even experienced runners can correctly identify their foot-strike pattern only about half the time. This may be, at least in part, because many runners, especially distance runners, vary their foot-strike patterns during the course of a run.

It also turns out that a noticeable change in foot-strike pattern isn’t necessary to reduce injury risk factors in runners. Researchers from the Cleveland Clinic, for example, found that increasing step rate—which has previously been associated with reduced impact forces—only affected foot-strike pattern in a small percentage of runners (see “Step rate manipulation and foot-strike pattern,” September, page 51). More recently, Australian researchers reported that running in minimalist footwear had no effect on foot-strike pattern for the study group overall, despite a significant shifting of work from the knee to the ankle.

Interestingly, although the interventions in these two studies were not associated with a change in foot-strike pattern, they were associated with significant changes in foot inclination angle. And it makes sense that, if the foot hits the ground at less of an angle, that can still have measurable effects even if the change isn’t large enough to reclassify a heel striker to a midfoot striker. The Australian study also noted a significant shift in strike index (the location on the long axis of the foot of the runner’s center of pressure at initial contact), which researchers sometimes use to define foot-strike pattern. Again, strike index didn’t change enough to warrant foot-strike pattern reclassification, but did change enough to have made a difference in other ways.

These developments underscore the need for runners and the clinicians who treat them to focus less on foot-strike pattern as an outcome measure. Training goals based on variables like step rate or step length are easier to implement, and are likely to benefit a greater percentage of runners—even those who prefer to keep their shoes on.

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