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Windlass mechanism

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Feb 28, 2018.

  1. scotfoot

    scotfoot Well-Known Member

    Members do not see these Ads. Sign Up.
    So during the gait cycle the windlass mechanism is engaged and reversed twice . Going from heel strike to heel strike we have windlass , reverse windlass , windlass and then reverse windlass at toe off . Yes ?
  2. scotfoot

    scotfoot Well-Known Member

    So in this short clip we have windlass ,reverse windlass ,windlass ,reverse windlass ?
    Haile Gebrselassie slowmotion left barefoot - YouTube

    upload_2018-2-28_11-12-2.jpeg ▶ 1:04

    6 Oct 2014 - Uploaded by Light Feet Running / Le Guide du Crawl Moderne
    Comprendre le bon geste de la foulée (course de fond) par Courir Léger / LightFeet Running (LFR) - Duration: 5 ...

  3. scotfoot

    scotfoot Well-Known Member

    So with regard to the above , the toe extensors contribute to arch stiffness during early stance by dorsiflexing the hallux and lesser toes and tensioning the plantar fascia . As stance progresses and ground reaction forces build , it seems likely that the prestrike , dorsiflexed position of the hallux/lesser toes will allow the plantar fascia and plantar intrinsics to load over a greater period of time reducing the stresses to which these tissues are subjected and so reducing the chances of plantar fasciitis developing .
    Question .Can the first of the two windlass cycles during gait be significantly inhibited by footwear ?
    Last edited: Mar 1, 2018
  4. efuller

    efuller MVP

    Yes, you could say that describes the motion. Or you have minimal tension in the plantar fascia, high tension in the plantar fascia, minimal tension in the plantar fascia.
  5. scotfoot

    scotfoot Well-Known Member

    Hi Eric ,

    So the extensors contribute to foot stiffness .

    In the case of a foot with intrinsic foot muscle atrophy caused by diabetic neuropathy , the foot likely becomes a less effective lever during gait , especially during late stance . As we discussed in a previous thread , the musculo/neural/skeletal system may , through the information received by proprioception inputs , slowly adapt to the changing capabilities of the foot by causing gait to be altered in such a way as to reduce the work load of the forefoot during toe off . Thus a high stepping gait or a shuffling gait may develop .

    However , I believe it is plausible that intrinsic muscle atrophy may also , in part , be compensated for by increased activity of the external toe flexors . Increased use of the toe flexors would tension the plantar fascia during midstance and late stance giving a more rigid lever and more proximal plantar pressures during these phases of stance .

    Using the extensors in this way may lead to permanent extension of the proximal phalanges of the hallux and lesser toes , giving rise to cocked /claw toes . The fat pad under the met heads would migrate distally giving rise to pressure problems and ,over time the entire forefoot may start to curve upwards .

    A cavus foot would also likely develop as the plantar fascia is tensioned by the extrinsic toe flexors to compensate for reduced plantar intrinsic input .

    Could all of this be greatly helped by a podiatrist led ,conservative approach to the intrisic foot muscles using an appropriately prescribed and supervised progressive resistance exercise ?

    Back to Dr Karen Mickle and her trial . "Evaluating a foot strengthening exercise program to improve foot function and foot health in older adults with diabetes"

    What do you think ?

    Last edited: Mar 2, 2018
  6. efuller

    efuller MVP

    We often take a short cut when discussing stiffness. The short cut is that we assume that stiffness is the same in all directions. When the foot is weight bearing gravity pulls the body down and ground reaction force pushes the bottom of the foot upward. Those forces will tend to cause a bending moment on the foot in a particular direction. To resist that bending moment you need compression in the bones and tension on the bottom side of those bones. So, the extensors cannot contribute to weight bearing stiffness and will tend to increase bending of the foot. As to the idea that the extnesors put tension in the fascia to increase stiffness. This doesn't work either. In the video that you posted above, you can see extensors active during swing phase and then are not visibly active during stance phase. The plantar fascia is a passive structure that will contribute to foot rigidity.

    Contraction of the toe flexors will tend to decrease tension in the plantar fascia. Increased plantar tension will tend to make foot more rigid.

    There is a phenomenon called extensor substitution. This the unusual firing pattern of the extensors during the stance phase of gait. I don't every recall seeing a research paper on this phenomenon that explains why it happens. Clinically, you will see this. Without having done a study, my sense is that you tend to see this phenomenon when there is forefoot or midfoot pain. My theory on this, is that the exstensor contraction (including the anterior tibial muscle) is a pain avoidance behavior. This pain avoidance behavior could lead to contractions of the toes. A contraction is a situation where the joint capsule becomes shortened and does not allow motion that was previously available. If the full range of motion of the joint is frequently used I doubt that a contraction would develop. So, if someone has exstensor substitution they could possibly prevent joint contractures by doing active, and or passive range of motion excercises.
  7. scotfoot

    scotfoot Well-Known Member

    Quote -
    "As to the idea that the extnesors put tension in the fascia to increase stiffness. This doesn't work either. "

    So are you saying ,that if I sit with my foot off the ground and dorsiflex my hallux by contracting the toe extensors , tension in the plantar fascia will not cause the metatarsal head of the first ray to move towards calcaneus ?
  8. efuller

    efuller MVP

    What I am saying is that contraction of the extensors will tend to make the foot more flexible (in the direction of plantar flexion of the rearfoot and dorsiflexion of the forefoot) when weight bearing.

    To increase rigidity you need tension on the bottom. Using tension on the top to create tension on the bottom doesn't increase rigidity.
  9. scotfoot

    scotfoot Well-Known Member

    "Using tension on the top to create tension on the bottom doesn't increase rigidity."

    It does if the active tensioning component on the top (the extensor muscles ) and the passive band on the bottom (the plantar fascia ) are directly connected to each other ,in this case via their attachments the the base of the proximal flange .

    As a simple thought experiment think of a flexible . shatterproof 12 inch ruler with a small roller placed at one end . Now imagine a thin leather belt lying along the underside of the ruler ,over the roller and then back along the top of the ruler .Imagine also the base of the ruler and the underside section of the belt are fixed in place in a vice of some description . Ok ,now pull on the upper free end of the belt . The ruler will curve upwards as you have indicated .

    However if you start off with a ruler which is already configured in an arch shape ,similar to the foot , then you will find that the arch deepens as you pull on the upper end of your belt .It will not invert back the other way . The arch / belt system will become better at resisting forces acting the straighten out the ruler -it is more rigid .

    So it is with the arch of the foot ,the extensors and the plantar fascia .
  10. efuller

    efuller MVP

    The problem with your thought experiment is that you are not testing rigidity. You need to create the physical model and try and bend it.
  11. scotfoot

    scotfoot Well-Known Member

    Just borrowed a ruler from reception and a belt from around my middle . The system is harder to bend and more rigid .
    So there are 2 windlass phases . A primary phase which involves active dorsiflexion of the toes before heel contact then plantar flexion during weight acceptance , and a secondary windlass phase which starts with passive dorsiflexion during later stance then moves to active plantarflexion of the toes during toe off .
    The primary plantar phase is likely affected by footwear unless a spacious toe box is present .
  12. scotfoot

    scotfoot Well-Known Member

    So if you have a primary Windlass phase as well as the accepted secondary Windlass phase ,then can the efficiency of the primary phase be improved by increasing the range of motion of the toes in dorsiflexion .
    Might an increased range of motion of the toes produced by Rathleff's exercises be the key component of his treatment regime ?

    High-load strength training improves outcome in patients with ... - NCBI

    1. Similar
    by MS Rathleff - ‎2015 - ‎Cited by 39 - ‎Related articles
    Scand J Med Sci Sports. 2015 Jun;25(3):e292-300. doi: 10.1111/sms.12313. Epub 2014 Aug 21. High-load strength training improves outcome in patients with plantar fasciitis: A randomized controlled trial with 12-month follow-up. Rathleff MS(1), Mølgaard CM(2), Fredberg U(3), Kaalund S(4), Andersen KB(3), Jensen TT(4) ...
  13. scotfoot

    scotfoot Well-Known Member

    Here is a good slow motion film showing what I am presently calling the primary and secondary Windlass mechanism phases .

    I have no idea who Ken Bob is , but bet he does not know he may have a fine example of a primary Windlass going on , which may be preventing excessive loading of his plantar fascia !
    Barefoot Ken Bob slow-motion on treadmill - YouTube

    upload_2018-3-7_20-5-33.jpeg ▶ 0:40

    17 Aug 2010 - Uploaded by Ken Bob Saxton
    Harvard University, Dr Daniel Lieberman's Skeletal Biology lab Note the subtle fore-foot landing. I'm not ...
  14. scotfoot

    scotfoot Well-Known Member

    To better understand the impact that the primary Windlass mechanism would have in reducing stresses in the plantar fascia during the weight acceptance stage of gait , the following analogy may be of use

    . Imagine a simple 3 oz fishing weight hanging by a 2 foot long thread , from a tables edge . Now imagine lifting the weight upwards about 6 inches then dropping it again . Let's say the rapid loading of the thread causes the thread (representative of the the plantar fascia ) to snap . Now imagine you include a six inch piece of elastic into the mix , in place of six inches of the thread ,so that the weight is now suspended at the end of a 1.5 foot long thread joined to six inches of elastic . Repeat lifting and dropping the weight and the thread is loaded less rapidly which protects the thread from damage . The elastic represents the toe extensor muscles connected to the plantar fascia via the bases of the proximal phalanges .

    Thus , in my opinion , the primary or initial Windlass mechanism could make a great deal of difference to tissue loading during gait . To function properly the initial Windlass phase ( initial may be a better word than primary ?) is reliant on an adequate range of motion of the toes around the metatarsophalangeal joints , adequate strength in the toe extensors , appropriate neurological control , and non restrictive footwear where present ( Looking at the video above restrict footwear would be anything that significantly interfered with the movement of the foot )

    Any thoughts ?
  15. Dr. Steven King

    Dr. Steven King Well-Known Member

    To pull the conversation from the flat hardtops to the trails.

    I have noticed a large load on the plantar fascia when i trail "run" downhill on higher degrees of slope 15-25 degrees.
    At these steeper angles most foot strikes are with the forefoot (toe-in toe-down) and the heel never touches the ground.
    This is different than just running barefooted on your toes on a flat surface.

    What is going on with the windlass system during this situation?

    Please provide a scientific definition with testable parameters for the term "restrictive footwear".
    I build combat footwear systems that "restrict" blast fragments from injuring soldiers lower limbs.
    I hope you understand why we need a good definition that is agreed upon.




  16. scotfoot

    scotfoot Well-Known Member

    Hi Steve
    If you land on the ball of your foot , and your toes are dorsifexed prior to foot contact by the active contraction of the extensors ,then as strain is introduced into the plantar fascia during weight acceptance , eccentric contraction of the toe flexors will allow the toes to plantarflex thus "paying out " the wound portion of the fascia . This initial /primary windlass mechanism occurs when foot contact results in toe plantarflexion of previously actively dorsiflexed toes .
    As gait progresses ( and without heel contact in the downhill case you have highlighted ), the COG passes the foot and the toes revert to a more dorsiflexed position and then contribute to toe off .

    The idea of the "wound " plantar fascia being "paid out" to resist damaging loads is analogous to line being pulled from a fishing reel by a charging fish .

    "Please provide a scientific definition with testable parameters for the term "restrictive footwear"."

    Sorry Steve . Not even remotely my job .


  17. scotfoot

    scotfoot Well-Known Member

    I'm curious .
    What sort of ideas have you employed to combat foot injury from blasts ? Is it just about materials or are other design features involved ?

  18. scotfoot

    scotfoot Well-Known Member

    My understanding is that if you place a small explosive charge on top of a piece of hamburger meat and detonate it it will do little damage to the meat ,but that if you wrap the meat around the charge much more damage is done . ( PLEASE DO NOT TRY THIS AT HOME !) .
    So an explosive force will do less damage if can dissipate in all directions .
    Have you considered developing a shoe/boot with a sole that will yield under the force of a small anti personnel mine ,to give an essentially empty gap between the foot and the ground at the moment when most damage would normally occur ?
  19. Dr. Steven King

    Dr. Steven King Well-Known Member

    Aloha Gerrard,

    I must apologize to the other readers of this thread if i am going off subject a bit.
    Windlass is important.

    Your questions on puncture and blast resistance are the best ones i have taken here on Podiatry Arena yet. Thanks for caring.
    Here is an intro primer for the gait tech thus published for the public.
    It will be these systems that help my Dad, a 20 year stroke survivor, walk better and safer.

    Materials and Design features must work together to improve soldier safety comfortably.

    Advanced Composites such as the aramids (Kevlar) , UHMUPE Spectra, or regular pressed carbon fiber offer high amounts of puncture and blast resistance.
    But they are hard, harder than concrete when built correctly, so how do you make something hard act soft?
    Make into a spring.
    Take a look at the mechanics on the short 30 second video on our website at www.kingetics.com.
    We are using 4 simple machines in a closed kinetic chain to improve gait efficiency over the current single simple machine used today for shoe with the foam drop that creates a declining plane.
    It also could be considered a double lever by the spring plate lifting the rearfoor as well as the cradle lifting the rearfoot to create a declining plane.
    We have done phase 1 bench top testing for the US Department of Defense on the orthotics which all the results are posted under the MAREN tab on the website for your review.

    Most foot docs and biomechanical researchers are not understanding the mechanics of this system nor how it can help reduce the strain and work by the windlass systems.
    That is too bad since they must have had the physics training that explains it.

    If kitchen floor mats are made out of 100% polyurethane PU blown foam,
    And the current NATO combat boots are mandated to be made out of 100% polyurethane PU blown foam,
    Then our soldiers are protecting our lands and loved ones whilst fighting with kitchen floor mats!
    IF A=B and B=C then A=C oh no not that higher math!!

    Levers Do Work...


    Subject Matter Expert for ASTM American Society of Testing Materials committees;
    -E54.4 Homeland Security Applications and Personal Protective Equipment, Tactical Body Armor
    -F13 Pedestrian and Walkway Safety Footwear Testing and Standards
    -F48 Exoskeletons and Exosuits

    Co-Principle Investigator SBIR A11-109 “Advanced Composite Insoles for the Reduction of Stress Fractures.” US Department of Defense and Army Medical Research and Materials Command
  20. scotfoot

    scotfoot Well-Known Member

    Hi Steve ,

    No problem with going on to another subject at this point in the thread as all that needs to be said about the two phases of the Windlass mechanism , the initial or primary phase and the secondary phase , has more or less been said . The idea of the initial Windlass phase seems to be a new one but is , in my opinion , completely correct . The "paying out " of the plantar fascia and the subsequent, controlled , lengthening of the foot during weight acceptance will clearly reduce tissue stress not least in the fascia itself .

    This may not be a welcome idea to those who talk about the lengthening of the foot , during normal gait , causing harm to the plantar fascia and asks questions of footwear that unseats during the swing phase of gait , if the toes are actively dorsiflexed .

    With regard to the information you have supplied , above ,anything that improves quality of life is to be welcomed .


  21. Dr. Steven King

    Dr. Steven King Well-Known Member

    This is such a good question an i bet it would be connected to 90% of all repetitive running injuries and 75% of mechanical deformities.

    "Can the first of the two windlass cycles during gait be significantly inhibited by footwear ? "

    Perhaps another way of stating the question with the mindset of an O&P practitioner would be,
    Can the first of the two windlass cycles during gait be significantly supported-assisted by footwear-orthotic modalities?

    Now if we could only get every podiatry college to test this and to compare results with all available footwear+orthotic systems including the current blown foams with custom plastic insoles and the above proposed mechanical advanced composite simple machine systems.

    Windlass Is a Blast !

  22. efuller

    efuller MVP

    Gerry, can you explain how paying out of the plantar fascia reduces stress in anything? Paying out is like tying a rope to a weight and throwing the weight off of the roof. When the weight reaches the end of the rope there will be increased stress in the rope.
  23. scotfoot

    scotfoot Well-Known Member

    Eric ,
    Imagine you have a rope wound around a drum a few times and then attached to a weight . Imagine also , that the rotation of the drum can be influence by an adjustable friction brake .
    Ok , so now put the brake of full so that the drum does not turn at all . Throw the weight off the roof and as soon all the slack is taken up the rope will be pulled suddenly tight ,and if the weight is great enough and travelling fast enough , the rope will snap .

    Now go back and adjust the brake on the drum so that it pays out line as desired . Now , when the weight drops and all the free line is used up , the drum can still rotate paying out more line against resistance bringing the weight to a more gradual stop . The drum and friction brake represent the initial engagement of the windlass and the eccentrically contracting toe extensors respectively .

    I suppose another way of seeing the same thing would be the action of arrestor wires on an aircraft carrier . It's about kinetic energy and not just static forces .

    Steve ,
    I agree that things should be reevaluated with the initial Windlass in mind . A blank sheet of paper may be required .


  24. scotfoot

    scotfoot Well-Known Member

    So here is a paper which confirms the pre-tensioning of the plantar fascia , pre heel strike , by way of activation of the toe extensors (1) P Caravaggi et al 2009 .

    In my opinion , and in a counter intuitive twist , this pre-tensioning results in less tension in the plantar fascia during weight acceptance than would otherwise be the case .If you like , it prevents a rapid "tension transient" in the fascia during weight acceptance and ameliorates the potentially damaging effects of high levels of kinetic energy in the tissues of the foot as a whole .

    An enlightening paper .

    Quote -
    "The simultaneous action of the ankle dorsiflexors and toe extensors, which prevent foot-slap and dorsiflex the toes at the MTPJ, and the plantarflexion moment applied to the calcaneus by the vertical ground reaction forces could account for some pre-stretching of the PA. A MTPJ dorsiflexion angle of about 30 deg. was measured for the three subjects thus confirming the action of the toe dorsiflexors at and prior to heel-strike (Table 4).
    Indeed, a recent study has proposed that early stance preloading of the PA may be beneficial to propulsion during walking (Pataky et al., 2008). While the present study strongly suggests that such preloading exists, without further experimental and/or modelling studies, we can only speculate as to the possible advantages of such preloading. Loading the PA at heel-strike is likely to reduce the crimp present in unloaded collagenous tissues (Butler et al., 1978), thereby resulting in earlier arch stiffening and helping to ensure that, as the propulsive phase begins, a greater proportion of force is transferred by the foot to the ground."

    Paper (1)
    A dynamic model of the windlass mechanism of the foot: evidence for ...

    by P Caravaggi - ‎2009 - ‎Cited by 60 - ‎Related articles
    This is the so-called windlass mechanism which, in the late phase of stance, is responsible for raising the arch of the foot (Hicks, 1954) and contributing to stiffening of the foot by pulling on the heel, causing inversion at the subtalar joint and `locking' the midtarsal joint (Briggs and Tansey, 2001). Previous studies using finite ...
  25. scotfoot

    scotfoot Well-Known Member

    Question .
    Is their a clear relationship between a limited range of dorsiflexion of the toes and an increased rate of plantar fasciitis ( hallux limitus ) ?
  26. scotfoot

    scotfoot Well-Known Member

    Ok ,so now I am a bit confused .The plantar fascia is thought to support the arches of the foot during loading of the foot . However there seems to be a disconnect between the ground reaction forces shown to exists during weight acceptance (force plates ) and strain calculated to exist in the plantar fascia ,using cadaveric studies or finite models (see above ) , during the same stage . In my opinion it would appear that the models /cadaveric studies are significantly flawed .

    Also ,answering my own question (see above ) ,there would appear to be a link between hallux limitus and plantar fasciitis .
  27. efuller

    efuller MVP

    When you talk about stress reduction you should mention which structure you are talking about. In the above example, the friction brake (toe extensors) are under more stress. Yes the ankle dorsiflexion muscles will slow forefoot loading which will reduce peak force at forefoot loading.
  28. efuller

    efuller MVP

    What is the problem you see with the force data and plantar fascia strain?

    Yes, there is a link between hallux limitus and plantar fasciitis. Tension in the fascia causes limited hallux dorsiflexion. The structures involved are both part of the windlass mechanism.
  29. scotfoot

    scotfoot Well-Known Member

    Eric ,
    After chewing things over I have less of a problem with force plate data and plantar fascial strain than I did but believe that max strain in the fascia is at heel off .
    Other than that I am quite happy with my contribution to the thread .

  30. efuller

    efuller MVP

    I"m bumping this thread back to the top because the subject was creeping into another thread.
    Gerry can you restate your theory on the multiple windlass phases?
  31. scotfoot

    scotfoot Well-Known Member

    Hi Eric
    I appreciate the courtesy but feel that the existence of two windlass phases has as much relevance to a thread on foot function as anything else the thread in question contains .

  32. The other thread is a discussion of the Root paradigm, Root didn’t mention the windlass mechanism, once.
  33. Simon, as far as my personal experience in hearing both Drs. Mert Root and John Weed lecture a number of times, and from their few books and few published articles, I believe you are absolutely correct. The Windlass Effect of Hicks was never mentioned by them in their lectures. The first that I heard about the Windlass Effect of Hicks was from Dr. William Sanner when he lectured to us at CCPM during our first or second year. Bill did the Biomechanics Fellowship before Rich Blake but after Ron Valmassy. After Dr. Sanner left CCPM, he went on to be the Chairman of the Department of Biomechanics at the Pennsylvania College of Podiatric Medicine for about five years. I went to interview for that position as Biomechanics Department Chairman at PCPM in March 1988, 30 years ago, when Bill Sanner was getting ready to move on to another position.

    I really don't think that either Mert Root or John Weed had a good handle on ligament or plantar fascia biomechanics. In one often-told story, Dr. Root thought that a foot with its plantar ligaments all cut would not sag in the longitudinal arch. He was proved wrong, obviously, but thought that "joint congruity", by itself, would stabilize the foot. At least that is how the story goes, if true.

    In my many personal interactions with Dr. Weed, he was not impressed that the plantar fascia could exert significant force on the foot since it was not a muscle. I thought that was rather odd for someone as smart as Dr. Weed to believe such a thing.

    Jack Morris, DPM, showed me the "reverse windlass" by having a subject hang their toes off an orthoposer, having the toes all plantarflex, and having the calcaneus evert further when the hallux plantarflexed due to the reduction in plantar fascial force during my CCPM Biomechanics Fellowship in about 1985.

    I went back to Dr. Weed to talk to him about this observation that Dr. Morris and I made together and Dr. Weed said that he didn't think the plantar fascia could exert that much force on the foot since it wasn't a muscle. That is the first time I realized that my favorite biomechanics professor, Dr. John Weed, didn't know everything about foot biomechanics. In retrospect, this opinion was likely shared by Dr. Root since the windlass mechanism was rarely mentioned at all during my 5 years at CCPM. I had already read all of Hicks' papers by then and was lecturing to students at the time on his concepts. Reading Hicks' papers during my Biomechanics Fellowship was a like a bright light shining through the murkiness of Root biomechanics for me at the time. Everything that Hicks wrote I could understand. No "Root Biomagic" in anything that Hicks wrote, from what I could see at the time.

    A little side story about Dr. Jack Morris. Jack came back to CCPM to teach in the Biomechanics Department in 1984, right when I started my Biomechanics Fellowship (Morris JL, Jones LJ: New techniques to establish the subtalar joint's functional axis. Clinics Pod Med Surg., 11(2):301-309, 1994. Scherer PR, Morris JL: The classification of human foot types, abnormal foot function, and pathology. In Valmassy RL (ed) Clinical Biomechanics of the Lower Extremities. Mosby, St. Louis, 1996, pp. 85-93).

    Jack Morris was a real gem, was a great clinician, and was very funny (he was also a classmate of John Weed). We would often hang out together in the Biomechanics Clinic where I talked to him about his clinical techniques. He liked talking to me since I would bring him up to speed on the latest biomechanical techniques and ideas being used and discussed by the CCPM Biomechanics Professors at the time.

    I vividly remember Jack laughing many times with me about how when we left CCPM to start private practice 15 years earlier that everyone had forefoot varus at CCPM 15 years ago, and when he returned, everyone had forefoot valgus. In fact, the "Forefoot to Rearfoot Measurement Device" that we were urged to buy, didn't say "Forefoot to Rearfoot Measurement Device" on it, it said "Forefoot Varus Measurement Device".

    This says a lot about how much the measurement technique for forefoot to rearfoot relationship changed over the years at CCPM under the influence of different Biomechanics Professors. It also says a lot about the questionable accuracy in forefoot to rearfoot measurements over the years within the CCPM Biomechanics Department and why attempts to make accurate measurements of these parameters will always have significant intra-examiner errors.
  34. rdp1210

    rdp1210 Active Member

    So to get back to you Gerry about the two phase function of the windlass mechanism. I don't spend much of my time on podiatry arena, so it's hard to follow some of the more interesting aspects.

    I'm going to agree with you that we spend almost all of our time discussing the tension in the plantar fascia during the propulsive period of gait.

    I will share with everyone a mathematical calculation of the force in the plantar fascia for a rigid lever, single hinge tie beam model, that I sent to Kevin several years ago.
    Plantar fascial tension.jpg

    We know that inversion torsion on the forefoot against the rearfoot also stretches the medial slip of the plantar fascia. Therefore we could conclude that tension on the plantar fascia medial slip would tend to have a limiting inversion action of the forefoot. Limiting inversion of the forefoot to the rearfoot would limit the amount that the rearfoot can evert relative to the ground.

    This really does deserve a lot more research. I'll talk to Erin Ward next week at I-FAB more about it.
  35. scotfoot

    scotfoot Well-Known Member

    Hi Daryl ,
    Happy to leave it with you and I-FAB .

  36. scotfoot

    scotfoot Well-Known Member

    Hi Eric ,
    Post 5 contains a repeated typo which may be confusing things .

    "However , I believe it is plausible that intrinsic muscle atrophy may also , in part , be compensated for by increased activity of the external toe flexors . Increased use of the toe flexors would tension the plantar fascia during midstance and late stance giving a more rigid lever and more proximal plantar pressures during these phases of stance ."

    This should of course read --

    "However , I believe it is plausible that intrinsic muscle atrophy may also , in part , be compensated for by increased activity of the external toe EXTENSORS . Increased use of the toe EXTENSORS would tension the plantar fascia during midstance and late stance giving a more rigid lever and more proximal plantar pressures during these phases of stance "

    Sorry about that and hope it makes my views clearer .



    Ps Also post 5 -"A cavus foot would also likely develop as the plantar fascia is tensioned by the extrinsic toe EXTENSORS to compensate for reduced plantar intrinsic input ."
  37. scotfoot

    scotfoot Well-Known Member

    Hi Daryl
    Any feedback from iFAB re the initial phase of the windlass mechanism ?


  38. Dr. Steven King

    Dr. Steven King Well-Known Member

    Does anyone have an animated clip of the windlass mechanism of the lower extremity?


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