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Harvey Mudd College stilettos : Short Heels and Big Calves - Biologist Anna Ahn examines the human leg

6.5

20 March 2011

People come in different shapes and sizes, and Anna Ahn, assistant professor of biology at Harvey Mudd College, recently examined ten barefoot test subjects to see why calf muscle size in humans varies considerably.

Her study, "Variability of neural activation during walking in humans: Short heels and big calves," was published in the latest edition of the Royal Society journal Biology Letters. It reveals that the length of our heels, or the distance beween our ankle joint and the back of the Achilles tendon, seems to have an impact on the development of the size of our calf muscles.

"Similar to pulling a door-closer to its hinge, the ankle must be extended by a greater force when muscles pull closer to the ankle joint with a shorter heel," says Professor Ahn. "And heel length may determine calf muscle size in humans."

Ahn and her colleagues found that, in order to generate these higher forces at the ankle, "these individuals activate their relatively thicker muscles for a longer duration." Shorter heels therefore may mean larger calf muscles in many people.

One possible cause for the different shapes of calf muscles is the inherent difference in neural signals sent to these muscles during walking. In sedentary adults, the variability in neural control of the calf muscles was examined with muscle size, walking kinematics and limb morphometrics.

Professor Ahn's research focuses on the neural control and mechanics of animal locomotion. "We take an integrative and multi-disciplinary approach to examine the different levels of organization that influence the behavioral output of the neuro-musculo-skeletal system in animals such as frogs, lizards, tarantulas, and even humans," she says.