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Short heels and big calves

PainSci » bibliography » Ahn et al 2011
Tags: biology, barefoot, anatomy, biomechanics, running, foot, leg, limbs, pain problems, exercise, self-treatment, treatment, etiology, pro

One article on PainSci cites Ahn 2011: Does barefoot running prevent injuries?

PainSci commentary on Ahn 2011: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

Why does calf muscle size in humans vary so much? (It really does.) The bulkiness of the calf is an amplified sign of what kind of heel bone you have.

Specifically, Ahn et al. showed that calf size is probably driven by how far the heel bone projects backwards. They studied ten people of similar overall height and weight, lower limb length, and foot length and found that they were divided evenly: half were short-heeled with big-calves, and half had longer calcaneuses and more slender calves. They also looked at the neurology of the muscle recruitment. Folks with short heels and big calves were also using their medial gastrocnemius more than the lateral. So not only were their calves big, but they were pulling harder with the inside half of their gastrocs. By contrast, long-heeled humans appear to have more evenly distributed calf contractions.

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

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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