Laird Harrison

June 02, 2014

ORLANDO, Florida — US Army personnel who strike the ground heel-first when running do not suffer significantly more overuse injuries than those who do not, a new study shows.

"The bottom line is that we need to be very cautious changing someone's running style," first author Maj. Bradley Warr, PhD, from the US Army Research Institute of Environmental Medicine.

Dr. Warr presented the findings here at the American College of Sports Medicine 61st Annual Meeting.

Over the past decade, running barefoot or in minimal shoes has become increasingly popular.

Advocates argue that these choices cause runners to strike the ground with the front or middle part of the foot, allowing the ankle to attenuate some of the shock. They say this could reduce overuse injuries, particularly in the knee. Some previous studies have supported this hypothesis, but they have been relatively small.

The Army allows soldiers to choose their footwear for training, as long as they wear shoes with a closed toe box, and many minimal styles of shoe meet this criterion.

Foot-strike Patterns

Dr. Warr and his colleagues wanted to know whether teaching soldiers not to strike with their heels could reduce injury rates.

They took videos of soldiers running to evaluate foot-strike patterns. Of the 1027 soldiers evaluated, 232 were women, mean age was 26.1 years, and 83% struck the ground heel-first.

The researchers then looked at the medical records of the soldiers, who came from 5 military bases, to see whether the patterns correlated to musculoskeletal injuries.

The rate of overuse injuries was not significantly different between the heel strikers and nonheel strikers (18% vs 15%; P = .58).

The rate of heel striking was not significantly different between women and men (85% vs 82%; P = .30).

More women than men reported overuse injuries (27% vs 14%), but foot-strike pattern didn't correlate to these injuries in either sex.

Real Runners

The findings didn't convince Irene Davis, PT, PhD, director of the Spaulding National Running Center at Harvard University in Cambridge, Massachusetts, and a leading advocate of barefoot running.

"Some [of the soldiers] were in transportation, and they don't run very much at all," she told Medscape Medical News. "Some were infantry and they run a little bit, but there is a big group who don't run. I think that's a big flaw of that study."

In addition, she pointed out that the study was retrospective and that the injuries were self-reported rather than diagnosed by experts.

Dr. Davis cited a study of 52 members of the Harvard cross country team that showed double the rate of injury in those who struck with their heels (Med Sci Sports Exerc. 2012;44:1325-1334).

"To me, that's a better, more controlled group with more valid results," she said.

Dr. Davis and her colleagues have completed a prospective controlled trial in which a group of barefoot runners are compared with shod runners. They are now preparing to submit that study for publication.

Dr. Warr acknowledged that most of the subjects in his study were not endurance runners, but he sees this as a strength. "These data may be more representative of the typical recreational runner in the United States," he explained.

He and his colleagues are planning to follow the same soldiers and record their injuries prospectively.

Even if the Army doesn't end up recommending that the average soldier avoid heel striking, such a change in gait might benefit people who are getting injured, said Dr. Warr.

"Maybe it's more a tool to be used in practice than as a blanket policy," he said.

Dr. Warr and Dr. Davis have disclosed no relevant financial relationships.

American College of Sports Medicine (ACSM) 61st Annual Meeting: Abstract 2977. Presented May 30, 2014.

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