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Sunday, August 8, 2010

High heels; stiff tendons

Women who routinely wear high heels sometimes complain about discomfort when they switch to flats. Marco Narici and his team from Manchester Metropolitan University along with Robert Csapo from the University of Vienna have discovered why. The prolonged wearing of high heels results in stiff Achilles tendons and shorter muscle fibers.

Conventional wisdom says that constantly wearing high heels permanently shortens one’s calf muscles. The researchers tested this theory by comparing eleven women who said they were uncomfortable in flats with nine women who did not wear high heels. Contrary to what was expected, the calf muscles of both groups were the same size. In other words, high heels did not shorten their wearers’ calf muscles. However, when the team measured muscle fiber length, it was a different story. The calf muscle fibers were 13% shorter in high heel wearers.

A similar story unfolded when the scientists examined the women’s Achilles tendons. Both groups had tendons with the same length, but the high heel wearers had much thicker, stiffer tendons than the control group.

These two factors, shorter muscle fibers and stiffer tendons, work in concert to allow high heel wearers to maintain ankle strength and motion while wearing high heels. Shorter muscle fibers have to contract to a much higher percentage of their total length to achieve the same affect, and the stiff tendon allows them to do this. However, the price is that women with stiff Achilles tendons may feel discomfort when stretching the tendon out far enough to wear flat shoes.

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