Women who regularly wear high heels were found to have shorter calf muscle fibers and thicker, stiffer Achilles tendons than women who wear flat shoes, which could explain the discomfort reported by women who wear high heels when walking on flat feet.
Using MRI and ultrasound, Robert Csapo, from the University of Vienna, Austria, and colleagues assessed the calf muscles and Achilles tendons in two gender- and age-matched cohorts. The first group consisted of 11 women, age 20 to 50 years, who reported regularly wearing high heels greater than 5 cm for more than 2 years, and the second group was made up of nine women who did not wear high heels, according to a Journal of Experimental Biology press release.
“We were expecting slightly smaller muscle volumes in the high-heel wearers because we thought that if the muscle is in a shortened position then you are loading it less and the muscle volume should be smaller,” Marco Narici, co-author of the study, stated in the press release.
Although the calf muscles were found to be the same size in both groups, the release stated that muscle fibers of women in the high heel group were 13% shorter than those of the flat shoe group.
“This confirmed the hypothesis, because when you place the muscle in a shorter position, the fibers become shorter,” Narici said.
To discover whether the shortened muscle fibers made it more difficult for women in the high heel group to walk efficiently, the investigators turned their attention to the Achilles tendon. Using MRI, they could see that the tendons were shorter and thicker in the high heel group, according to the release.
Csapo and colleagues determined that, by thickening and stiffening, the Achilles tendon was compensating for the shortened muscle fibers in the calf muscle, allowing the calf muscles to function optimally while walking in high heels, but causing discomfort when walking on flat feet because the tendon cannot stretch sufficiently.
The investigators stated in their abstract, “We conclude that long-term use of high-heeled shoes induces shortening of the gastrocnemius medialis muscle fascicles and increases Achilles tendon stiffness, reducing the ankle’s active range of motion. Functionally, these two phenomena seem to counteract each other since no significant differences in static or dynamic torques were observed.”