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The intrinsic foot muscles and overpronation

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Oct 27, 2019.

  1. scotfoot

    scotfoot Well-Known Member


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    Within the content of a recent thread is some material which might be worth closer scrutiny . Any thoughts ?


    Material
    "Would you agree that push off from the contralateral foot helps prevent over pronation in the reference foot during walking . That is , the push off phase helps move the center of mass from between the two feet to immediately above the talonavicular joint in the reference foot ?

    A recent experiment (Farris et al , see below ) has shown that with a tibial nerve block to prevent the contraction of the foot intrinsics , push off could not be fully completed during gait and that participants adopted a shorter stride pattern and increased hip muscle activity .

    My interpretation of these changes in motor strategy is that through executive function , the body quickly adapts to loss of push off force and hence incomplete shifting of the COM in the transverse plane during gait , by adopting a shorter stride and using abnormal hip activity .

    During gait , if the COM cannot be moved from between the feet to over the foot with each stride , then gravity driven pronation will be a problem .

    In short , intrinsic foot muscle deficits lead to abnormal gait and ,in my opinion , possibly to pathological pronation . "


    1. The functional importance of human foot muscles for bipedal ...


      https://www.pnas.org › content

      by DJ Farris - ‎2019 - ‎Cited by 12 - ‎Related articles17 Jan 2019 - Contrary to expectations, the intrinsic foot muscles contribute minimally to supporting the arch of the foot during walking and running. However, these muscles do ...
      Last edited: Thursday at 6:37 PM
      scotfoot, Thursday at 6:12 PMReport
      #34Reply
    2. [​IMG]
      scotfootWell-Known Member
      Question ; If deficits in the intrinsics can impair push off and so alter gait , can such deficits also cause problems during weight shifting , the most common time for the elderly to suffer falls ?
      If an older person wishes to shift weight but lacks push off power then might a more difficult to control " lean/sway strategy " be employed ?

      Interesting .​
      Gerrard Farrell

      Glasgow
     
  2. scotfoot

    scotfoot Well-Known Member

    This is an interesting quote from the Farris paper -

    "The reduction in moments about the MTP joint with the nerve block are in line with our estimates of what the PIMs are capable of contributing. We approximated the moment arm of PIMs about the MTP joint to be 1.5 cm (23) and calculated a potential moment contribution of 6 N·m about the MTP joint (using the same muscle parameters as earlier). Although a small moment, this is approximately half the peak MTP joint moment during walking and 20% of the peak in running . "

    "Half the peak moment..." . I am surprised by this level of contribution but it may help explain ,at least in part , the gait changes seen in some diabetic patients with foot involvement and atrophy of the intrinsics .

    Very useful paper .
     
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