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"Auto-support" of the foot

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Simon Spooner, Nov 30, 2009.

  1. Mart

    Mart Well-Known Member

    If not tonight . . . . then . . . . . . sometime . . . . we all should . . . . think about how we think. Otherwise our thinking might be


    the world is F***** lets party

    http://www.gogolbordello.com/

    which is of course may be a well considered viewpoint

    :drinks
     
  2. Its been good for me and I´m sure lots following along. Thanks for taking the time.

    Looking forward to the next person who says something about the windlass mechanism I can ask ´of which toe´and link the thread.
     
  3. "Thanks for being on the show." :santa: Here's the caveat, I don't know if what I have said is right or wrong, it's just my thoughts at the time of writing. I have been known to write total cobblers here on more than one occasion.......:eek:
     
  4. It finally looks like the dust is starting to settle a little bit on this very popular thread so I think I can now squeeze in a few thoughts on the subject of "auto-support".

    First of all, I devoted a whole chapter in my latest book on the subject of "Transmission of Forces and Moments with the Foot" from a series of newsletters I wrote from May 2006 to July 2006. In this chapter, I analyzed first how forces are transmitted from one rigid object to another in a series of rigid objects, then I discussed how four rigid objects with "plantar" hinges will develop compression forces between them when an external loading force is applied to their distal aspect, and finally I discussed how the unique structural arrangement of the bones, plantar ligaments and Achilles tendon within the human foot is designed so that moving the center of mass of the body from posterior to anterior over the foot will produce a progressive stiffening of each of the metatarsal rays/columns of the foot as external loading force is increased plantar to the metatarsal heads (Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 23-30).

    Here is an excerpt from the last three paragraphs of the last newsetter of that chapter:

    Instead of calling this mechanical effect of the foot "auto-support", which is a term I don't like since it is too non-specific, I propose that the replacement term of "passive load-dependent forefoot dorsiflexion stiffness" be used to describe this passive mechanical characteristic of the human foot. With passive load-dependent forefoot dorsiflexion stiffness, the forefoot passively becomes more stiff (i.e. this may be demonstrated in a cadaver foot with no muscular force being required other than the resisting force offered by the gastrocnemius-soleus complex) as GRF is progressively transferred from the plantar rearfoot to the plantar forefoot and the gastrocnemius-soleus-Achilles tendon complex resists the forward acceleration of body during late midstance.

    For those of you who have not read the original papers of John Hicks, the mechanical concept of the windlass effect was fully explored by Hicks in his papers on the subject (Hicks JH: The mechanics of the foot. II. The plantar aponeurosis and the arch. J Anatomy. 88:24-31, 1954.
    Hicks, J.H. The Three Weight Bearing Mechanisms of the Foot. Pages 161-191 in F.G. Evans (ed): Biomechanical Studies of the Musculoskeletal System. C.C. Thomas Co., Springfield, Ill. 1961.) Hicks describes not only the arch raising effect of hallux dorsiflexion which he called the windlass effect and also describes the "reverse-windlass effect" of the passive digital plantarflexion that occurs in the cadaver foot with plantar loading of the metatarsal heads. Those of you who are truly interested in this subject should read these papers a few times since you will likely appreciate, as I have, how far Hicks was ahead of the others of his era in understanding the mechanical importance of the plantar aponeurosis during normal function of the foot.

    Finally, I would like to complement Michael, Martin and Dave for the progress they have both made over the past few years in their understanding of these complex subjects and their willingness to share their thoughts with others here on Podiatry Arena. It is very rewarding and exciting for me to see such high levels of intellectual discussion occurring here on Podiatry Arena, being led by the likes of Drs. Spooner and Fuller. These events give me great hope for the future of the international podiatric biomechanics community in the coming decades.

    Thanks to everyone for a very interesting discussion!:drinks
     
  5. Mart

    Mart Well-Known Member


    Some of these threads turn in to great little seminars; without them I would live in a podiatric vacumm most of the time and I suspect that is true for others too.

    As always, thanks for your (plural) encouragement, candour and time.

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  6. efuller

    efuller MVP

    Abstractions can help if they are valid and well thought out. The term windlass mechanism of the foot is an abstraction that describes the interaction of the plantar fascia and the bones of the foot. We can all refer back to the paper by Hicks that Kevin sited to get a definition of the abstraction.

    Autosupport does not have that definition.


    What you are making the case for is not abstraction, but empirical use of data. Empirial use of data goes along these lines. If I see a callus under the first metatarsal head I will put a reverse Morton's extension under that foot. If I do this 10 times and eight of those patients feel better with the modification than without the modification then I can empirically prescribe that modification whenever I see a callus under the first metatarsal head. I did not explain why that modification worked, I just did it in response to what I saw.

    Now, if I used an F-scan and saw a particular gait pattern and I made a modification that most of the patients liked then I could empirically add that modification. There is no explanation of why it works. The concept of autosupport is an explanation of why modifications work. I just don't feel that it is a very good explanation. And if you treat emprically, you don't need that explanation.

    Regards,

    Eric
     
    Last edited: Dec 3, 2009
  7. Mart

    Mart Well-Known Member


    Thanks Eric I take your points.

    My use of the word abstraction was not a good one I should have used concept as you have.

    That will teach me to go using them hifollutin words, I shoud stick to em 4 letter uns :sinking:.

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootinic.com
     
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