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Thursday, February 3, 2011

Why stilettos are the secret to shapely legs

Thanks to Linda V for the link!

Why stilettos are the secret to shapely legs
from the telegraph

From bunions to back pain, high heels are blamed for all manner of ailments but, in a rare piece of good news, scientists say that stilettos can give you more shapely legs.

A new study found that women who wore high heels activated their inner and outer calf muscles more evenly than those who wore flatter shoes, which gave their legs a more symmetrical appearance.

Flatter heels, as worn by half the subjects in the study, caused "lopsided" development, as the inner calf muscles were exercised more and grew larger, according to the findings published in the Royal Society journal Biology Letters.

Prof Anna Ahn, of Harvey Mudd College in Claremont, California, said: "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." She said that the thick inner calf muscles were activated for a longer duration to generate these higher forces at the ankle.

In the study, the researchers analysed 10 sedentary people - five men and five women - to ensure athletic training was not a factor in their performance.

In a separate study two years ago, Italian researchers found that moderately high heels could tone the pelvic muscles.

The study involved measuring electrical activity in the pelvic muscles of women when they held their feet at different angles. Those who held their feet at a 15-degree angle to the ground, the equivalent of a 2.75in heel, showed up to 15 per cent less electrical activity in their pelvic muscles.

The results suggested that the muscles were more relaxed when women wore higher heels, increasing their strength and ability to contract.

Ahn AN, Kang JK, Quitt MA, Davidson BC, Nguyen CT (2011) Variability of neural activation during walking in humans: short heels and big calves. Biology Letters. doi: 10.1098/rsbl.2010.1169

People come in different shapes and sizes. In particular, calf muscle size in humans varies considerably. 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. Half the subjects walked while activating their medial gastrocnemius (MG) muscles more strongly than their lateral gastrocnemius (LG) muscles during most walking speeds (‘MG-biased’). The other subjects walked while activating their MG and LG muscles nearly equally (‘unbiased’). Those who walked with an MG-biased recruitment pattern also had thicker MG muscles and shorter heel lengths, or MG muscle moment arms, than unbiased walkers, but were similar in height, weight, lower limb length, foot length, and exhibited similar walking kinematics. The relatively less plastic skeletal system may drive calf muscle size and motor recruitment patterns of walking in humans.

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