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  1. #3

    Re: Foot stiffness and footwear

    Hi Karl ,
    The paper you reference could not really be more relevant since it was when I was considering its contents that I came up with the theory outlined in the first post .
    I liked their currency bill idea and the comparison to a fishes fins (see below ) .The concept of a “geometrically flat ,yet functionally curved “ structure was new to me and might well account for some arch stiffness ,although as stance progresses through toe off I feel that the distal transverse arch will become structurally curved as well as functionally curved .

    I also liked their idea of energy storage in the transverse ligament but feel that more energy will be stored than they have calculated due to the metatarsal head movement detailed in my first post .

    Some time ago a paper was published that proposed that the intrinsic muscles of the foot helped stabilise the foots skeletal structures so that other larger muscle groups could operate more efficiently (1).

    If a currency bill arrangement of the metatarsals does come into being in the foot during gait , partly via the way the metatarsals are attached to the tarsal bones and partly due to the “metatarsal parabola” then I can see the value of stabilizing this structure and feel that Mckeons paper has real merit .

    I placed a few posts on the paper you mentioned on another site and have included these below

    Regards
    Gerry

    (1) The foot core system: a new paradigm for understanding intrinsic - NCBI
    https://www.ncbi.nlm.nih.gov/pubmed/24659509
    by PO McKeon - ‎2015 - ‎Cited by 60 - ‎Related articles
    21 Mar 2014 - The foot core system: a new paradigm for understanding intrinsic foot muscle function. McKeon PO(1), Hertel J(2), Bramble D(3), Davis I(4).



    1.

    Contribution of the transverse arch to foot stiffness in humans
    Ali Yawar, Lucia Korpas, Maria Lugo-Bolanos, Shreyas Mandre, Madhusudhan Venkadesan
    (source)
    #scotfootActive Member
    So appendages can be "geometrically flat, yet functionally curved " . So does the human foot have a functional , distally placed ,transverse arch ?

    Gerry
    Gerrard Farrell
    Glasgow


    2.
    scotfootActive Member
    Further to posts 3 and 4 above ,some time ago I wrote the following -

    Extract
    "First I found myself a suitable surface such as linoleum . Next I took off my shoes and socks and stood next to a wall for support . Then , taking most of my weight initially on the right foot which was kept flat on the ground ,I put my left foot into toe off position so that only the ball of the foot and the toes were in contact with the ground . Then I carefully transferred some weight onto the left foot and finally,with the ball of the foot and toes under some pressure , rotated the foot outwards producing torque . I found that the toes played an important part in resisting the outward rotation and that they also began to become spaced out from each other possibly engaging the adductors .( please note that I am not suggesting that anyone copy the above exercise sequence or injury may result )
    So perhaps the toes can significantly aid grip on a flat rigid surface ? "

    After reading the paper mentioned in post 3 (1) , it now seems plausible to me that toe and hence metatarsal head splaying caused by the torque produced during the foot movement detailed in the extract above ,might produce a more marked currency bill folding effect than forefoot weight bearing alone . Hence increasing foot stiffness in response to increased foot torque during walking /running .

    Gerry
    (1)
    (Contribution of the transverse arch to foot stiffness in humans
    Ali Yawar, Lucia Korpas, Maria Lugo-Bolanos, Shreyas Mandre, Madhusudhan Venkadesan
    (source)
    Gerrard Farrell

    Glasgow





    3.
    scotfootActive Member
    This video analysis (1) of a fishes fin helps to explain their hypothesis . For my part , although the hypothesis as it applies to the foot may account for a small part of the stiffening of the foot , I believe that the distal transverse arch makes the majority of its contribution to arch stiffness via a different mechanism .

    Gerry
    (1) Video illustrating the mechanism underlying curvature-induced ...

    [IMG]file:///C:\Users\pubuser\AppData\Local\Temp\msohtmlclip1\0 1\clip_image001.jpg[/IMG] ▶ 1:04

    29 May 2017 - Uploaded by Shreyas Mandre
    Curvature-induced stiffening of a fish fin, Khoi Nguyen, Ning Yu, Mahesh M. Bandi, Madhusudhan Venkadesan ...
    Gerrard Farrell

    Glasgow






    4.
    scotfootActive Member
    I do think the theory proposed in the Ali Yawar et al study, above, may have some validity but I do not believe their study protocol is a valid way of testing it .Nor do I believe the mechanism they describe plays a major role in foot stiffness .

    In addition ,in my opinion the study below (1) and all such studies do not show that there is no distal transverse arch function but instead show that there IS .
    1
    Z Orthop Ihre Grenzgeb. 1995 Jul-Aug;133(4):335-40.
    Ultrasonic measurements (n = 172) and plantar pressure investigations (n = 119) are performed on the forefeet of healthy adults, in order to constitute a correlation between shape and function of the anterior metatarsal arch. The thickness of the sole of the foot has its maximum beneath the 2nd metatarsal head and its minimum beneath the 1st and 5th ray. The highest pressure values are found at the 2nd and 3rd metatarsal head. It is concluded that despite the arch like configuration of the forefoot there is no structural arch function. The biological principle of adequate padding of pressure points results-depending on the load-in a different thickness of the soft tissues of the sole of the foot. The higher pressure under the central metatarsal heads is accompanied by thicker soft tissue pads and a more dorsal position of these rays.​
    Gerrard Farrell

    Glasgow
    Last edited by Gerrard Farrell; 07-01-2017 at 02:35 PM. Reason: Spacing of text

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