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Transverse arch stiffness and ankle and hip joint moments

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Mar 27, 2017.

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  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

    Members do not see these Ads. Sign Up.
    Evaluation of the relationship between the static
    measurement of transverse arch flexibility of the
    forefoot and gait parameters in healthy subjects

    Takashi Kondo, RPT, MS, Takeshi Muneta, MD, PhD, Tsutomu Fukui, RPT, PhD
    J. Phys. Ther. Sci. 29: 413–418, 2017
     
  2. Admin2

    Admin2 Administrator Staff Member

  3. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Contribution of the transverse arch to foot stiffness in humans
    Ali Yawar, Lucia Korpas, Maria Lugo-Bolanos, Shreyas Mandre, Madhusudhan Venkadesan
    (source)
     
  4. scotfoot

    scotfoot Active Member

    So appendages can be "geometrically flat, yet functionally curved " . So does the human foot have a functional , distally placed ,transverse arch ?

    Gerry
     
  5. scotfoot

    scotfoot Active 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)
     
  6. scotfoot

    scotfoot Active 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 ...

    upload_2017-6-25_10-59-45.jpeg ▶ 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 ...
     
  7. scotfoot

    scotfoot Active 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.​
     
  8. scotfoot

    scotfoot Active Member

    So the hypothesis ,which may be old hat or even wrong is as follows .

    I began by looking at a radiograph of the human foot taken from the dorsal aspect . In the forefoot area , this clearly shows that the metatarsals extend distally to differing degrees . I have heard a line which connects the metatarsal heads called a" metatarsal parabola " so lets just go with that for now . This parabola is in the horizontal plane but is this arrangement which gives rise to the arch during the transition of the foot through late stance .

    Consider as an analogous structure to the metatarsals ,the fingers of the hand .
    Place your hand flat on a desk with the finger tips a few mm apart (ignore the thumb )
    Now keeping the finer tips in place on the desk ,lift the hand off the desk ,pivoting around the finger tips till you reach an angle between the fingers and the desk of about 70 degress . Now look at the fingers relative to each other . They have formed an arch structure . (Think of a piece of guttering about a foot long pushed into sand at an angle of 70 degrees .The part of the guttering you can see above the sand is similar to the finger structure you have created on the desk top and similar to the metatarsal arch formed when a foot , flat on the floor ,transitions towards toe off with the toes becoming more dorsiflexed .

    So how is energy stored in this system ? Back to the hand again .
    If you try the above hand /desk experiment you will notice that the middle fingers of the four need to bend to stay in the same spot on the desk . With a transitioning foot .this bending is probably replaced with a forward displacement of the second and third metatarsal heads and associated toes causing energy to be stored in the distal transverse ligament .

    So do the metatarsal heads of the first and second lesser toes move distally, relative to the other toes , as the toes move into a dorsilflexed position ? You can easily try this out for yourself by taking off your shoes and socks .sitting in a chair and moving your foot from a flat position to a position with the heel raised and observing toe movements ,but for me the answer was yes .

    The above also explains pressure distribution under the forefoot .

    So that is the theory in rough form .

    What say you to the above Simon ?

    Regards

    Gerry
     
    Last edited: Jun 27, 2017
  9. scotfoot

    scotfoot Active Member

    Taking the previous six posts as a whole , it seems quite possible that the transverse arch of the foot provides the majority of the foot stiffness required for energy efficient gait . It also seems likely that the distal transverse arch becomes more pronounced as the forefoot is loaded and the toes become more dorsiflexed .
    With regard to maintaining foot structure then , perhaps the primary role of the intrinsic muscles of the foot is to help maintain the integrity of the transverse arch of the foot and not the longitudinal arch .
    For example the oblique head of the adductor hallucis could be viewed as a torsion resistant cross strut of the transverse system .

    Gerry
     
  10. scotfoot

    scotfoot Active Member

    Looking at posts #8 and #9 could a prosthetic foot be made which mimics the mechanism discussed ?

    Gerry
     
  11. efuller

    efuller MVP

    Once the heel lifts off of the ground in gait, maintaining the transverse arch is not the problem. The problem is maintaining the rigidity of the longitudinal arch.
     
  12. scotfoot

    scotfoot Active Member

    Surely its about maintaining the rigidity of the foot as a whole to provide an effective lever and not about maintaining the rigidity of merely one sagittal section .A 2 dimensional system on its own would be poor at resisting torque .
     
  13. efuller

    efuller MVP

    You have to look at the forces that are applied to the foot. In gait, in propulsion, there is the upward pull of the Achilles, the downward force of body weight applied to the top of the talus, and upward ground reactive force at the metatarsal heads. Those forces cause stresses in the sagittal plane and not the frontal plane. A transverse arch, if there was one, would be loaded by offset forces in the frontal plane.
     
  14. scotfoot

    scotfoot Active Member

    Eric ,
    In post #8 above I wrote the following " Think of a piece of guttering about a foot long pushed into sand at an angle of 70 degrees " . Lets adjust that and make the guttering of a plastic material and of about 3 feet long . It is still pushed into the sand at about 70 degrees and its convex surface is uppermost (the opposite of the way it might be used on the side of a house ) . Now imagine placing one hand at the free end of the guttering and twisting . The guttering will flex but not as much as it would if a transverse curvature was not present through out its length . Hence a transverse cross section strengthens the guttering and resists longitudinal distortion .

    I am not sure that many would dispute the existence of a transverse arch at the level of the tarsal bones . What I am saying is that as gait progresses the "metatarsal parabola " causes conversion of the distal aspect of the metatarsal from functionally non arched to functionally arched . The transverse arch therefore ,extends from the metatarsals into the fore foot and helps provide foot stiffness when it is most required .

    Of course the medial longitudinal arch performs specific support and energy storage functions but in the tarsal/metatarsal section of it length it is also part of the transverse system . The medial longitudinal arch thus helps provide resistance to the forces you described in your post and as part of a transverse system resists torque . The transverse system helps provide the foot , as a unit , resist both torque and the forces you describe .( My understanding is that bones resist both compression and stretching better than they do flexion .
     
    Last edited: Jul 8, 2017
  15. scotfoot

    scotfoot Active Member

    Further to the above if we look again at the plastic guttering planted at 70 degrees in the sand . Imagine placing your hand half way down the length of the guttering and pressing down .This represents body weight . If you now also pull up on the free end this represents the pull of the achilles tendon . The guttering will flex under these forces but not as much as it would if the plastic were not transversely arched throughout its length . The same principle applies to the mid and forefoot giving stiffness .
     
  16. efuller

    efuller MVP

    [
    The difference between guttering and the foot is that the guttering is uniform material and the foot is made of ligaments and bones. Engineers have terms for this: isotropic and anisotropic. Collagen is a very good example of an anisotropic material. Collagen is is made up of bundles of fibers. It has much more strength in the direction of the fibers and very little strength perpendicular to the direction of the fibers. So, we could look at the orientation of the collagen in the ligaments and see if there are a significant amount of fibers oriented transversely. The foot as whole is anisotropic. It resists loads better in some directions better than others.

    Where, exactly, are saying the transverse arch is? It's obviously not at the metatarsal heads.

    I also don't understand what torque you are referring to when you say the transverse arch resists torque.
     
  17. scotfoot

    scotfoot Active Member

    Please consider the following thought experiment . First take a disc of wood with a thickness of 1 inch and a diameter of six inches and divide this into two equal semicircular parts . Next orientate the two arched sections vertically and directly facing each other and about six inches apart . Next create 5 equally spaced holes in the two facing surfaces about one inch up from the bases . Next take a length of bamboo cane ,of about six inches in length and fix its ends into hole 1 of the two facing arched sections .Do the same with the remaining 4 facing holes in the arched sections . Now imagine the whole thing glued together .

    You should now have a mental picture of something resembling a toast rack .
    Now pick up the construction by the two ,arched end pieces ,one in each hand . Rotate the hands inwards ,applying force and the construction flexes .

    Now picture a second construction but this time the holes are NOT placed along a straight line one inch up from the bases of the arched end pieces (respectively , the under tension transverse ligament and tarsals ) but instead place them following the curvature of the arch so that bamboo connectors (the metatarsals ) help form part of a transversely arched structure which better rests flexion (like a piece of guttering ) .

    Where is the transverse arch ? It varies during gait ( see post #8) . But from and including the tarsals ,along the metatarsals ,and into the forefoot during late stance .

    What torque ? The torque produced in the foot during gait . ( If you walk on a slippy ,newly polished floor in you socks then you can feel the foot slip and rotate outwards . )
     
  18. scotfoot

    scotfoot Active Member

    In summary then the transverse arch can be viewed as being composed of five saggital sections ,each of which corresponds to a metatarsal and a component of the transverse arch of the metatarsals . Each of these sections is further composed of ligaments and by a component of the plantar fascia .

    For example the most medial of the saggital sections ( which is a part of the medial longitudinal arch ) is composed of the tarsal arch ,the first metatarsal ,ligaments and part the plantar fascia .

    So we have not two longitudinal arches in later stance but five ,which are in turn united by common origin and insertion to give a transverse arch (tarsal arch and transverse ligament -see previous post ) .
    During later stance the existence of a "metatarsal parabola " causes the five longitudinal arches to give rise to a distally placed transverse arch which then taken as a whole provides the necessary stiffness for this phase of gait .

    I have omitted the intrinsic foot muscles from the system because increasingly I see their role (other than helping to control toe movement ) as being pivotal in maintaining the transverse arch of the foot during later stance . However they do this not primarily by resisting body weight but rather by controlling the configuration of the transverse arch . That is they make adjustments to the bony/ligamentous framework of the foot and this framework ,aided by the extrinsic foot muscles , supports the body during gait . (see PO Mckeon et al 2015 ) .

    If all of the above is true then weak or " under educated " intrinsics will eventually lead to major problems with the entire system leading perhaps to more proximal tissue failure .

    Any thoughts ?
    Gerry
     
  19. scotfoot

    scotfoot Active Member

    Below is a hopefully clearer version of post #18 .
    1. In summary then , the transverse arch can be viewed as being composed of five saggital sections ,each of which corresponds to a metatarsal and a component of the transverse arch of the tarsals . Each of these sections is further composed of ligaments and by a component of the plantar fascia ( overall , the foot can be thought of as having five longitudinal arches each composed of a metatarsal ,tarsal arch , calcaneus and talus supported by ligaments and the plantar fascia )

      The most medial of the saggital sections ( which is a part of the medial longitudinal arch ) is composed of tarsal arch ,the first metatarsal ,ligaments and the plantar fascia .

      So we have five metatarsals in the transverse arch ,which are in turn united by a common origin and insertion (tarsal arch and transverse ligament -see previous post ) .

      During later stance the existence of a "metatarsal parabola " causes the metatarsals to give rise to a distally placed transverse arch which ,when taken as together with the rest of the transverse arch , provides the necessary stiffness for this phase of gait .

      I have omitted the intrinsic foot muscles from the system because increasingly I see their role (other than helping to control toe movement ) as being pivotal in maintaining the transverse arch of the foot during later stance . However they do this not primarily by resisting body weight but rather by controlling the configuration of the transverse arch . That is they make adjustments to the bony/ligamentous framework of the foot and this framework ,aided by the extrinsic foot muscles , supports the body during gait . (see PO Mckeon et al above post 3 ) .

      If all of the above is true then weak or " under educated " intrinsics will eventually lead to major problems with the entire system leading perhaps to more proximal tissue failure .

      If this is all starting to look like very similar Mckenzies " half dome" and Mckeons (1) "foot core " expansion of the same , then that is because I think both ideas are valid since the existence of a metatarsal parabola would extend the half dome into the forefoot when foot stiffness is most required .


      Any thoughts ?
      Gerry
      (1)The foot core system: a new paradigm for understanding intrinsic foot ...

      bjsm.bmj.com › Archive › Volume 49, Issue 5
      by PO McKeon - ‎2015 - ‎Cited by 63 - ‎Related articles
      We then integrate the concept of the foot core into the assessment and treatment of the foot. Finally, we call for an increased awareness of the importance of the ...
      Last edited by Gerrard Farrell; Today at 05:59 AM. Reason: clarity​
     
  20. scotfoot

    scotfoot Active Member

    Bullet points -

    1 The transverse arch of the foot contributes more to arch stiffness than the longitudinal arches (see PDF below )

    2 If the transverse arch did not extended into the forefoot then ,since systems tend to fail at their weakest point , the forces acting on the foot during gait would tend to flex ,distort and perhaps fracture the metatarsals .

    3 The metatarsal parabola gives rise to ,or makes more pronounced ,the distal transverse arch during gait ,in the manner laid out in post #8

    4 The tensioned transverse ligament /metatarsal/tarsal arch component of the system means that the metatarsals are subject to compressive and stretching forces during gait and not flexion which they are less able to tolerate .This is explained in post #17

    5 One of the roles of the intrinsic foot muscles is to help regulate the transverse and longitudinal arches to ensure a proper distribution of forces throughout the foot .They must be strong enough to do this or foot pathologies are likely to develop .

    PDF

    curvature of the transverse arch governs stiffness of the human foot

    https://www.eiseverywhere.com/retrieveupload.php?...



    The stiffness of shallow thin shells has two asymptotic regimes, one that ... A. The human foot has two distinct arches in the longitudinal and transverse directions ..
     
  21. scotfoot

    scotfoot Active Member

    Hi Danaberg
    You have indicated that you think post #17 is "dumb " . Could you expand on that ?
     
  22. efuller

    efuller MVP

    Link does not work. I am very skeptical of the other arguments that you have posted in favor of the transverse arch contributing to stiffness of the foot. One of those arguments was about the muscles controlling the transverse arch. The vast majority of the foot muscles run anterior posterior and therefore can't "control transverse arch stiffness.

    I don't understand what you are saying here.
    Be more specific in your forces. For example, the ground reactive force acting on the 2nd metatarsal head....

    You make the assumption that the shorter metatarsals plantar flex to create a transverse arch. I've looked at many plantar pressure maps of gait and this does not happen.

    I did not see it explained in post 17. Ground reactive force on a metatarsal head and body weight applied through the bone proximal to the metatarsal head will create a bending moment in the metatarsal that will tend to cause tension on the bottom and compression on the top. Those forces within the bone resist flexion of the metatarsal.


    There is no evidence that muscles regulate the transverse arch. I've looked at many plantar pressure patterns and most of the time you don't see a pattern that you would need to see for a transverse arch at the metatarsal heads. I've looked at cadaver feet while pulling on the peroneus longus muscle. There is essentially no change the shape of the transverse arch.
     
  23. scotfoot

    scotfoot Active Member

    Morning Eric .
    You said
    " . I am very skeptical of the other arguments that you have posted in favor of the transverse arch contributing to stiffness of the foot. One of those arguments was about the muscles controlling the transverse arch. The vast majority of the foot muscles run anterior posterior and therefore can't "control transverse arch stiffness. "

    The transverse arch can be viewed as being made up of five sagittal sections which run anterior posterior . The muscles which run in the same direction can therefore contribute to control of the whole .

    You said
    " You make the assumption that the shorter metatarsals plantar flex to create a transverse arch"

    From this I realise that I have failed to explain the idea to you . Perhaps this is also at the root of Danaberg's problem . All I can suggest is that you build the model in post #17 .

    Gerry
     
  24. efuller

    efuller MVP

    Your description of the model is insufficient to build it. Could you build it and post a picture?

    Name the muscles that run in the same direction and then explain what they do to the transverse arch.
     
  25. davidh

    davidh Podiatry Arena Veteran

    You cannot have true rigidity in a living foot.

    The forefoot transverse arch doesn't exist. I don't know who first described it. It wasn't Gray or Carter in the 1858 Grays Anatomy (First Ed) - I looked.
    Although Carter (the illustrator and co-author of Grays) does a very nice illustration of the non-weightbearing foot stripped of muscles in which the contours of the foot are clear, including the medial longitudinal arch and the other "arches", these are not described as arches. That seems to have crept in later. We now find it in literature where the author has seen it described somewhere and repeated the error, and in anatomical foot models, along with the lateral transverse arch. Neither the forefoot transverse arch or the lateral longitudinal arches exist, and strictly speaking, the medial longitudinal arch isn't a true arch either, since it deforms under loading.
     
  26. scotfoot

    scotfoot Active Member

    Hi David
    You said
    " The forefoot transverse arch doesn't exist " and in part you are correct . It is not present during early stance but is through toe off .
    Indulge me for a moment or two . Place your hand flat on a table surface and imagine that your fingers represent the metatarsal of the foot and your knuckles the tarsal /metatarsal joints . Now look at your finger tips . For most people they will be arranged on the table top in a horizontal arch shape with the middle and ring fingers extending further across the desk top than the pinky and index fingers . Ignore the thumb .
    Ok so now ,whilst keeping the finger tips in contact with the table surface ,lift the heel of your hand off the table without bending the hand at the knuckle joint . Keep going till the unbent hand forms an angle of about 70 degrees with the table top . Now look at your fingers . You will notice that the two middle fingers of the four will be bent . Let them move forwards till they are straight but still with their tips in contact with the table top . You now have a distinct transverse arch .
    This is what happens with the metatarsals during gait when the foot moves from early stance through toe off .

    Does that make sense so far ?
    Regards
    Gerry
     
  27. davidh

    davidh Podiatry Arena Veteran

    You have described a mobile curve in the hand. You misunderstand the definition of an arch. I quote McMinn and co-workers from Colour Atlas of Foot and Ankle Anatomy (at the time of writing McMinn was a Professor of Anatomy at the University of London).
    "(and) the word arch suggests an architectural rigidity that does not exist." My bold for emphasis.

    Moreover - the transverse arch does not exist at toe-off in the healthy foot in the frontal plane, which I assume is what you mean. I am not aware of any study which shows this to be the case.
     
  28. scotfoot

    scotfoot Active Member

    McMinn does not say that the arch does not exist .He says architertural rigiidity does not exist . You have misunderstood the quote . Also , arches can flex (1)

    Finally "Moreover - the transverse arch does not exist at toe-off in the healthy foot in the frontal plane, which I assume is what you mean. I am not aware of any study which shows this to be the case."
    It is mechanically impossible for a the transverse not to exist at toe off if a significant "metatarsal parabola " exists .

    (1)
    Longest Flexible-Arch Bridge Planned | ASCE

    www.asce.org/magazine/20150210-longest-flexible-arch-bridge-planned/10 Feb 2015 - Construction will begin soon on the longest span bridge to employ a flexible arch that is shipped flat to a site for rapid deployment. featured
     
  29. scotfoot

    scotfoot Active Member

    Post #8 begins "So the hypothesis ,which may be old hat or even wrong is as follows ."
    It now seems it is old hat only to mother nature . Amazing .

    And its worth repeating . It is mechanically impossible for the transverse arch not to exist at toe off if a significant "metatarsal parabola " exists .

    And still not a single study into the mechanism by which the unshod foot interacts with a substrate to provide traction in the sense of grip during gait . Not one . Ever . Breathtaking .
     
  30. efuller

    efuller MVP

    As I said before, you are making the assumption that the metatarsals plantar flex and this is an erroneous assumption. All the metatarsal heads do not stay in contract with the ground as the heel lifts in gait. I've looked at many plantar pressure plots of people walking over a force plate. Additionally, when you watch people walk barefoot, from behind, you can often see that the fifth met head is off of the ground. It is mechanically possible for there to be no transverse arch.

    Eric
     
  31. scotfoot

    scotfoot Active Member

    Eric
    You said
    "As I said before, you are making the assumption that the metatarsals plantar flex and this is an erroneous assumption" I am not making this assumption and I don't understand where you are getting this from .
    And
    " Additionally, when you watch people walk barefoot, from behind, you can often see that the fifth met head is off of the ground. It is mechanically possible for there to be no transverse arch. "
    It does not matter if the fifth met head is off the ground so long as some are on the ground (3+).
    As I have tried to point out with my poorly received hand analogy , four or even three metatarsals would work in the same way as five .
    It is mechanically impossible for there to be no distal transverse arch at some stage during normal gait if a "metatarsal parabola is present " . (Normal in this case referring to average ground metatarsal head contact across a population )
     
    Last edited: Sep 4, 2017
  32. davidh

    davidh Podiatry Arena Veteran

    The answer to which is very simple - carry out a definitive study yourself.

    I'm done here. Thanks people.
     
  33. scotfoot

    scotfoot Active Member

    Its probably much easier to understand the above if you ignore all the stuff about fish fins . Its a red herring .
    Metatarsal parabola + terminal stance = distal transverse arch . Can't be any other way .

    Done .
     
  34. efuller

    efuller MVP

    Repeating the statement again does not prove it to be true.
    Looking at the big picture. Why should we care if there is a transverse arch? In some feet there is one and in others there isn't.
     
  35. scotfoot

    scotfoot Active Member

    "Why should we care if there is a transverse arch? In some feet there is one and in others there isn't."
    Could you clarify this please . Do you mean a distal transverse arch is present , in a significant number of people ,at all stages of gait ?​
     
  36. efuller

    efuller MVP

    I can't give you percentages. After looking at many steps on an EMED force platform I can say that it rare to see contact on first and 5th metatarsal heads and little pressure on 2,3 and 4th met heads. A lot of the time you will see close to body weight on just the first and 2nd metatarsal heads after heel off. Sometimes you will see even weight across all metatarsals. Sometimes (more often than just 1 and 5) you will see weight on only mets 2,3, and 4 after heel off. (an upside down arch) So, some of the time there is a distal transverse arch and sometimes there isn't.

    Big picture: Why do we care if there is a transverse arch?
     
  37. scotfoot

    scotfoot Active Member

    You can't see individual met pressures on a force platform . I assume you mean a pressure mat ? For the rest of your post please re read the thread but missing out the fish fin content .To understand the increased pressures under mets 2,3 and 4 post #26 should help .

     
  38. efuller

    efuller MVP

    Ok technically you are correct that the EMED is a pressure mat that is embedded in a box that looks like a force platform. The point is that if you look at individual foot steps, you have a hard time fitting the idea of a transverse arch into the data you see with the pressure mat. Feet are different. Only some of them have foot prints consistent with the notion that there is a transverse arch. Trying to impose the concept of a transverse arch on feet whose foot prints look like they don't have a transverse is a waste of time. The transverse arch is not a universal thing. Which goes back to the question: What do we explain with the concept of a transverse arch? Why do we care about the transverse arch? Are there better ways to explain why certain pathologies occur?
     
  39. scotfoot

    scotfoot Active Member

    Just because it shows green and not red on the results screen does not mean their is no pressure , just not as much.
    "Why do we care about the transverse arch ?" Because it is a key component for providing stiffness during terminal stance . It also provides a mechanism by which the metatarsals are subject to one of , compressive force or stretching , lonigitudinal tension rather than flexion which long bones are not good at resisting .
    This is explained in post # 17 .The one that Dananberg labeled dumb .
     
  40. efuller

    efuller MVP

    In your opinion it was explained in post 17. The problem with that explanation is the difference between a foot and your bamboo construct.

    If you want to understand foot stiffness you should do free body diagram analysis with specific bones and ligaments and have a good understanding of beam theory.
     
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