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Foot stiffness and the metatarsal parabola

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  • Foot stiffness and the metatarsal parabola

    This post concerns a recent paper published in Nature by Venkadesan et al ( see link below ) and an important error that affects some , but not all aspects of the paper .

    In a nutshell , as the ball of the foot begins to bear weight during gait ,the metatarsal heads splay mediolaterally ,the transverse ligament comes under increased tension , and the ball of the foot broadens .

    However , and critically , as gait progresses and the heel comes clear of the ground , the ball of the foot begins to narrow again , giving a more pronounced metatarsal arch in the distal aspect of the foot which is vital to foot stiffness during push off .

    The narrowing is a product of the different lengths of the metatarsals which gives rise to the metatarsal parabola .

    The narrowing of the ball of the foot is easy to prove by simply using a couple of thick paperback books and a flat surface . Just stand with both feet on the floor with the books touching either side of the ball area of the bare reference foot (the majority of your weight should be on the contralateral foot at this stage ).

    Now transfer 70 of your weight onto the reference foot with a careful emphasis of the ball of the foot . You should find that the books move apart as the met heads and ball of the foot splay . Now , keeping some weight on the contralateral foot for balance , lift the heel of the reference foot off the flat surface by about 45 degrees so that the ball of that foot supports about 70 % of your weight .

    Now look down at your reference foot and the books . Daylight has appeared between them . The foot has narrowed from is splayed configuration .

    In summary , as the heel clears the ground , relative to each other the met heads move apart anteroposteriorly and together mediolaterally .

    Stiffness of the human foot and evolution of the transverse ... › nature › articles
    4 days ago - In the foot, the material properties of the inter-metatarsal tissues and the mobility ... the plantar fascia and other longitudinally oriented ligaments and muscles, and do ... Therefore, the transverse curvature has the effect of amplifying the intrinsic ..
    Last edited by Gerrard Farrell; August 5, 2022, 05:49 AM.

  • #2
    Here is a video of a very simple model in operation . The ball represents the tarsals ,the pencils the metatarsals ( note; not the toes themselves ), and the cord connecting the metatasal heads or pencils represents the transverse arch . As my hand lifts the ball the heads of adjacent pencils move together mediolaterally and apart anteroposteriorly.

    A similar system exists, and I am being bullish here since geometry dictates it must exist, in the foot and this probably contributes a lot to foot stiffness during push off . Shoes with an inner that is concave transversely in cross section will likely interfere with the mechanism.