High heels stress muscles, pose injury risk—and change the way future women will walk?
If, over the next millennia, women will continue to use high-heeled shoes as modern women do, women in the future may evolve a tottering gait, walking with shorter, more forceful strides than men, with their feet perpetually in a flexed, toes-pointed position.
The long-term consequences of walking this way are yet unknown but will certainly be far-reaching and profound—not unlike the significant outcomes of Australopithecus afarensis hominids beginning to walk upright rather than in a crouched position like their distant cousins, the apes.
Just last July (2011), British scientists from three universities analyzed the famous prehistoric “Laetoli footprints” left by three A. afarensis individuals in eastern Africa about 3.7 million years ago—and concluded that this human ancestor had walked upright, in contrast to what was widely believed since the footprints were found in 1974.
Walking fully upright—or bipedalism—together with longer legs made it possible for prehistoric humans and hominids to travel longer distances and run farther and faster than before, say paleontologists, specialists that study early human biology, culture and environment.
It would take 2.2 million years more after the A. afarensis left their footprints before our hominids ancestors would be able to evolve a longer torso and bigger brain to complement the upright stance—all of which helped them to expand further out of Africa and effectively colonized the globe.
Now, Australian scientists who study the biomechanics of walking say that modern women who use high heels habitually are changing the way they walk—not only when they’re in their favorite stilettos, but just about all time: when they change into sneakers for a run or remain barefoot or stay still.
“Human movement requires a constant, finely tuned interaction between muscular and tendinous tissues, so changes in the properties of either tissue could have important functional consequences,” say Dr. Neil J. Cronin and his two colleagues at Griffith University’s Musculoskeletal Research Program in Queensland, Australia, who undertook the new study.
It’s obvious even to non-scientists that the millions of women who use high heels almost every day habituate to this and walk differently from those who usually wear flats.
But the nature and extent of the differences surprised even the Dr. Cronin and his colleagues. The findings of the study, likely the first of its kind, were published late in January (2012) in The Journal of Applied Physiology.
The researchers found that women who persistently wore heels moved with shorter, more forceful strides than women who did not, and their feet were always in a flexed, toes-pointed position called a “plantarflexed position.” This stride and position continued even when the women weren’t in heels. Consequently, fibers in their gastrocnemius or calf muscles had shortened—so that walking or running put much greater mechanical strain on the calves of heel wearers than on those of women who didn’t use heels often.
Men and women who didn’t wear heels often stretched and stressed their tendons, especially the Achilles tendon when they walked. But because wearing heels increased Achilles tendon stiffness, habitual heel wearers mostly engaged their calf muscles when walking.
This biomechanical distinction is critical, says Dr. Cronin, who is now a researcher at Finland’s University of Jyvaskyla, because it signifies that when they stretch and strain their already shortened calf muscles, heel wearers end up walking less efficiently—with or without heels—than their non-heeled counterparts.
Women who wear heels all the time also require more energy to cover the same amount of ground as people in flats, are more prone to muscle fatigue and have a higher risk for injury, researchers found.
“Several studies have shown that optimal muscle-tendon efficiency” while walking “occurs when the muscle stays approximately the same length while the tendon lengthens,” Dr. Cronin explains. “When the tendon lengthens, it stores elastic energy and later returns it when the foot pushes off the ground. Tendons are more effective springs than muscles,” he continues.