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Potentiation of the extrinsic toe flexors by the actions of the intrinsic toe flexors

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Aug 27, 2016.

  1. scotfoot

    scotfoot Active Member


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    During gait ,can the forces produced by the flexor digitorum longus be enhanced by the forces produced by the flexor digitorum brevis .

    I believe the answer to this question is yes since when both muscles act to produce force the flexor digitorum brevis helps to keep the toe phalanges extended relative to each other .

    Any thoughts

    Gerry
     
  2. scotfoot

    scotfoot Active Member

    With regard to the above , when the toes are flat on the ground and acted upon by the intrinsic and extrinsic toe flexors, the various intrinsic muscles act at differing points of insertion to prevent the phalanges being pulled out of alignment by the extrinsic toe flexors .

    This means that the toes do not curl or become clawed and provides a longer lever arm for the extrinsic toe flexors to act upon thus increasing the amount of force work they can do .

    Thus the intrinsic toe flexors have a direct effect on the amount of effective work the extrinsics can do .

    In my opinion the , actions of these two groups of muscles should not be considered without including ground reaction forces ,and their effects ,in the equation .


    This material is probably all in the text books long since but I have not yet come across it .

    Any thoughts ?

    Gerry
     
  3. efuller

    efuller MVP


    Don Green wrote an article published in the late 70's early 80's in JAPMA on the function of the muscles of the toes.

    I made a model of the toes and it was interesting to see that the effect of muscle tension was different for different starting positions. In some positions, the toes curled and others it did not. As you pointed out, when weight bearing there are competing moments caused by tension in the flexor tendons. There is the platntar flexion moment at each of the joints that will tend to compress the tip of the toe into the ground. There is ground reaction force at the tip of the toe that is trying to dorsiflex all the joints of the toe. Most people in static stance, when they contract their flexors will tend to get extension of the distal phalanx and plantar flexion of the proximal phalanx.

    I did some anatomical dissection on feet with and without hammertoes and the lumbricales did loose their mechanical advantage to plantar flex the mpj when the proximal phalanx was dorsiflexed on the metatarsal.
    Eric
     
  4. scotfoot

    scotfoot Active Member

    Hi Eric
    It has been shown that the intrinsic and extrinsic toe flexors are eccentrically active during heel off and through late stance in both walking and running .
    It has been postulated by some that this eccentric contraction of the intrinsic and eccentric toe flexors provides a balance to the dorsiflion moments at the MTP caused by ground reaction forces and that this contributes to the control of the forward falling motion of the body (Mann and Inman 1964 ,Reeser el al ., 1983)

    However,with regard to their action on the toes , I believe that the eccentric contraction of the toe flexors is not primarily about controlling COM progress but is simply about applying the toes ,which would otherwise simply passively dorsiflex, to the ground .

    Unlike the ball of the foot , gravity presses the toes into the ground only indirectly through the actions of the plantar fascia (windlass ) . I believe that the toes are principally pressed into the ground by the eccentrically contracting toe flexors which in the unshod condition is critical to providing both grip/traction and balance .

    What do you think ?

    Gerry
     
  5. efuller

    efuller MVP

    A body will fall forward when the center of pressure under the foot is posterior to the center of mass. (Neglecting momentum, but still considering moments that will have an affect on momentum.) When the long flexors contract, there will be a tendency to shift the center of pressure anteriorly under the foot. This will help control anterior posterior balance. The shift in center of pressure will be a couple of centemeters. The magnitude of the shift of the center of pressure from the long flexors will be smaller than can be achieved with contraction of the gastroc and soleus. Another factor in a-p balance in gait is placement of swing foot. If you want to slow down, you choose to place your foot further forward. So, the toe flexors do contribute a small amount to a-p balance in gait.


    I agree. As the load on toes increases, the load on the met heads decreases.


    When you analyze the toes you should carefully define what you mean by gravity. The force of gravity acting on the toes directly is negligible compared to all the other forces acting on the toes. The force of gravity acts on the whole body and will have to equal ground reaction force (plus or minus any vertical accelerations of the center of mass). The combination of body weighth (the force of gravity acting on the whole body) from above acting on top of the talus and ground reaction force pushing upward on the met heads will tend to dorsiflex the forefoot on the rearfoot. The dorsiflexion of the forefoot on the rearfoot will tend to increase tension in the plantar fascia and this tension will cause a plantar flexion moment on the proximal phalanx relative to the metatarsal. All the muscles that insert into the toes will also contribute moments to the joints of the toes.

    When you look at the problems that people have when there are missing toes, I tend to see more of high pressure problem under the metatarsal heads. These people don't tend to have gripping or traction problems. When they do have balance problems it's more related to the neuropathy that caused the loss of the toe. My feeling is that the toes are important for weight distribution on the forefoot. Pressure = force / area. The toes provide an increased area of contact, reducing pressure, especially after heel off. I think it would be very interesting to look at the toes of habitually unshod versus the habitually shod walking over loose gravel. My prediction is that the habitually unshod will have better and more muscular control of their toes to even out the pressures under the forefoot.

    Eric
     
  6. scotfoot

    scotfoot Active Member

    I think we are pretty much in agreement then that the toe flexors act eccentrically after toe off giving a more even distribution of weight across the forefoot area and that this is their principal role during this phase of gait rather than slowing the progress of the COM in a forward direction .

    I have to bow to your clinical knowledge that people with missing toes tend not to have gripping or traction problems but I feel that a missing hallux would be a major problem to those involved in barefoot activity . Shoes with good soles would substitute for the toes with regard to grip/traction in the shod condition .

    With regard to balance, the loss of toes might not lead to a discernible lack of balance during gait to the individual themselves but perhaps this is due to subconscious gait changes with reduced stride length and walking speed .

    A paper from 2014 (1) looked at the link between spatiotemporal gait characteristics and toe flexor strength and found as folLows -

    "In community -dwelling older people ,decreased strength of the toe flexor was correlated with slower walking speed ,shorter periods of single limb support phase ,and shorter stride length during fast pace walking . These data provide further support for an important role of toe flexor muscles in walking "

    The paper in question looked to the lack of propulsive capability in those with weaker toe flexors to explain the findings but I feel that a reduced ability to press the toes into the ground and evenly load the forefoot to give a broader platform for balance might also have played a role .

    Gerry

    Ref
    (1)
    Assciation between toe flexor strength and spatiotemporal gait parameters in community dwelling older people
    • Shogo MisuEmail author,
    • Takehiko Doi,
    • Tsuyoshi Asai,
    • Ryuichi Sawa,
    • Kota Tsutsumimoto,
    • Sho Nakakubo,
    • Minoru Yamada and
    • Rei Ono
    Journal of NeuroEngineering and Rehabilitation201411:143
    DOI: 10.1186/1743-0003-11-143

    © Misu et al.; licensee BioMed Central Ltd. 2014

    Received: 12 February 2014

    Accepted: 2 October 2014

    Published: 8 October 2014
     
  7. scotfoot

    scotfoot Active Member

    Whoops

    "I think we are pretty much in agreement then that the toe flexors act eccentrically after toe off" above should read
    "I think we are pretty much in agreement then that the toe flexors act eccentrically after HEEL off"
     
  8. scotfoot

    scotfoot Active Member

    Eric
    Some time ago I placed the following 2 extracts on a couple of websites . Given your greater knowledge of the anatomy and physiology of the foot do you think the mechanisms discussed in the posts are plausible ?
    Thanks
    Gerry

    extract 1

    By: blue23 May 2014, 16:55:42|blue[​IMG]


    Hi Jason
    I recently came across a paper from 2001(1) on the transverse mechanichal properties of skeletal muscle and I think that you might very well be right about training the toe flexors to help prevent injuy .
    My understanding is now that when passive muscle is subjected to transverse compression its behaviour can be predicted using an incompressible viscoelastic model (Ogden) . In addition passive skeletal muscle displays changes in stiffness to changes in rate of load application . Might the intrinsic muscles of the foot act to transmit load from the tarsal/metatarsal arch to the plantar fascia in the midfoot region and thus help to support the bony arch of the foot and help to avoid harmfull shearing and displacement forces between the articulating bones of foot ?
    Also ,in early stance as weight is transferred onto the foot causing a lowering and lenghtening of the tarsal/metatarsal arch and a tensioning of the plantar fascia, might compressive forces act through the passive muscle located between the bony arch and the plantar fascia to effect emptying of the plantar venous plexus ?
    Could changes in the composition of the plantar intrinsics predispose towards injury ?
    Kind regards
    Blue
    (1) Bosboom EM et al ; Passive transverse mechanical properties of skeletal muscle under in vivo compression ; J Biomech 2001 Oct 34(10)


    extract 2

    Gerrysays:

    November 16, 2014 at 11:22 am

    Hi Casey
    As outlined above I wondered if the plantar intrinsic foot muscles (PIFM) located between the bony arch of the foot (BA) and the plantar fascia might be subjected to passive transverse compression (PTC)when acted upon by these structures during early stance .
    I also wondered if ,during mid to late stance when the PIFM are active ,an increase in the stiffness of the “intrinsic core “might provide even greater support to the BA and its articulating joints .
    So the question for me is -Is there an increase in the intra and inter muscular pressure in early stance and can this be attributed to PTC ?
    An in vivo study to investigate this might involve indwelling intramuscular pressure sensors but why go down this road when such a sensor may already be in place in the form of plantar venous plexus (PVP).
    So can the PVP be looked at in this way? Is the pump emptied by inter-muscular pressure or by stretching and necking down ?
    NECKING DOWN-
    Since the veins of the plexus are elastic longitudinally and viscoelastic transversely the effective emptying of the PVP by stretching and necking down is ,in my inexpert view ,unlikely .
    So if necking down is not the mechanism of PVP emptying then the pump must be emptied by increased inter- muscular pressure .But what cases this ?
    If the pump empties in early stance when the plantar intrinsic muscles are not activated then the pressure must be created by stretching of the PIFM or by PTC.
    A study by BJ Broderick et al(1)showed that the PVP is emptied when a standing individual performs toe curls so it can be inferred that inter-muscular pressure is increased when the muscles become activated and contract. I believe that it is reasonable to think that inter-muscular pressure is therefore not increased when the same muscles become less active and return to their original more lengthened positions .
    So, in my opinion, it is most likely that in early stance the PVP is emptied by the passive transverse compression of the “intrinsic core” and indeed that the existence of a functioning PVP confirms the existence of a significant level of PTC . I also think it likely that the pressure generated in the pump reflects the inter and intra-muscular pressures generated within the “intrinsic core” and hence the pressures generated at the interfaces between the core and the plantar fascia and BA .
    I would welcome any comments on the above
    Kind regards
    Gerry
    Gerrard Farrell
    Glasgow
    Ref (1) Broderick et al -Venous emptying from the foot ; influences of weight bearing ,toe curls,electrical stimulation ,passive compression and posture 2010
     
  9. scotfoot

    scotfoot Active Member

    After considering the mechanisms outlined in the extracts above it seemed to me that if the intrinsics were to be the compressible and thus supportive core of the foot then the muscles and constituent fascicles making up this core must be able to apply force at their points of insertion without power loss through work partitioning . This is were the theory of hydraulically discrete fascicles came from .

    Cheers
    Gerry
    Hydraulically discrete fascicles in skeletal muscle - Biomch-L

    biomch-l.isbweb.org › Forums › ISB forums › Footwear Biomechanics Group
    13 Feb 2016 - 1 post - ‎1 author
    If the perimysium is sufficiently impermeable then might it be possible that each fascicle is able to function as a hydraulically discrete unit with ...
     
  10. efuller

    efuller MVP

    extract 2

    Gerrysays:

    November 16, 2014 at 11:22 am

    Hi Casey
    As outlined above I wondered if the plantar intrinsic foot muscles (PIFM) located between the bony arch of the foot (BA) and the plantar fascia might be subjected to passive transverse compression (PTC)when acted upon by these structures during early stance .
    I also wondered if ,during mid to late stance when the PIFM are active ,an increase in the stiffness of the “intrinsic core “might provide even greater support to the BA and its articulating joints .
    So the question for me is -Is there an increase in the intra and inter muscular pressure in early stance and can this be attributed to PTC ?
    An in vivo study to investigate this might involve indwelling intramuscular pressure sensors but why go down this road when such a sensor may already be in place in the form of plantar venous plexus (PVP).
    So can the PVP be looked at in this way? Is the pump emptied by inter-muscular pressure or by stretching and necking down ?
    NECKING DOWN-
    Since the veins of the plexus are elastic longitudinally and viscoelastic transversely the effective emptying of the PVP by stretching and necking down is ,in my inexpert view ,unlikely .
    So if necking down is not the mechanism of PVP emptying then the pump must be emptied by increased inter- muscular pressure .But what cases this ?
    If the pump empties in early stance when the plantar intrinsic muscles are not activated then the pressure must be created by stretching of the PIFM or by PTC.
    A study by BJ Broderick et al(1)showed that the PVP is emptied when a standing individual performs toe curls so it can be inferred that inter-muscular pressure is increased when the muscles become activated and contract. I believe that it is reasonable to think that inter-muscular pressure is therefore not increased when the same muscles become less active and return to their original more lengthened positions .
    So, in my opinion, it is most likely that in early stance the PVP is emptied by the passive transverse compression of the “intrinsic core” and indeed that the existence of a functioning PVP confirms the existence of a significant level of PTC . I also think it likely that the pressure generated in the pump reflects the inter and intra-muscular pressures generated within the “intrinsic core” and hence the pressures generated at the interfaces between the core and the plantar fascia and BA .
    I would welcome any comments on the above
    Kind regards
    Gerry
    Gerrard Farrell
    Glasgow
    Ref (1) Broderick et al -Venous emptying from the foot ; influences of weight bearing ,toe curls,electrical stimulation ,passive compression and posture 2010

    I remember seeing a video of with dye in the venous system and a device was used to compress the foot and you could see the venous blood move. The device partially mimicked weight bearing loads. So, it is likely, there is some passive mechanism to the movement of venous blood. I'm not sure if this supports either of the mechanisms that you describe.
    You mentioned the above, I believe, because you were theorizing the venous return might be a mechanism by which we could examine passive transverse compression of the muscles. From what I understand is that you are interested in seeing if passive transverse compression will be responsible for some of the tension developed by the intrinsic muscles.

    My feeling is that the amount of tension generated by the muscle will be largely determined by central nervous system activation of the muscle belly. If there is no CNS activation then the muscle can passively elongate in response to passive transverse compression

    Eric
     
    Last edited: Oct 7, 2016
  11. efuller

    efuller MVP

    The way to figure out if a muscle can support the bony arch is to look at its attachments and do a free body diagram analysis. Some of the intrinsic muscles have partial attachments to the plantar fascia. So, part of the force from the contraction of the muscle will be applied to the attachment of the plantar fascia to the bone.

    Beam theory says that when an object is supported on its end there will tension and compression within the strctures of the "beam." The intrinsics can be part of the the plantar structures that are under tension to prevent collapse of the bony arch. There is a lot of redundancy in plantar tension structures.

    The term harmful shearing and displacement forces is a little vague. The forces that you are concerned about should be better identified.



     
  12. scotfoot

    scotfoot Active Member

    Eric
    The theory is that the intrinsic muscles of the foot support the bony arch in two distinct ways .
    1 By producing force at the points of origin and insertion through eccentric and concentric contraction

    and

    2 by acting as a compressible core between the bony arch and the plantar fascia . A bit like the core of an old style ,wrapped elastic type golf ball .



    In chapter 5 of his Phd thesis Dr Luke Kelly found that there was a significant level of activation in flexor digitorum brevis . abductor hallucis and quadratus plantae at foot contact and that the activation levels increase as the foot is subjected to increased loading
    . I feel that this would make the mechanism of PVP activation through transverse compression more plausible . Similarly a more active body of musculature during increased foot loading would be less viscous and more able to act as a supportive core to the bony arch of the foot.

    CHAPTER FIVE – ACTIVE REGULATION OF LONGITUDINAL ARCH
    DEFORMATION AND RECOIL DURING WALKING AND RUNNING
    Luke A. Kelly 1
    Glen Lichtwark1
    Andrew G. Cresswell 1
    1 - The University of Queensland, Centre for Sensorimotor Performance, School of Human
    Movement Studies, Brisbane, Australia
     
  13. scotfoot

    scotfoot Active Member

    Above less viscous should read more viscous .
     
  14. The idea that the plantar venous plexus (PVP) of the plantar intrinsic muscles has anything to do with the structural integrity of the longitudinal arch of the foot is improbable at best. I am very familiar with Luke Kelly, PhD's excellent research on plantar intrinsic muscles. In fact, both Dr. Kelly and I will be lecturing on plantar intrinsic muscle function at the Biomechanics Summer School in Manchester, UK, in June 2017.

    The plantar intrinsics form part of what I have called the Longitudinal Arch Load-Sharing System (LALSS). The LALSS consists of multiple tension load-bearing elements within the plantar foot including the plantar fascia, plantar ligaments, plantar intrinsic muscles, and the peroneus longus, posterior tibial, flexor digitorum longus and flexor hallucis longus muscles. All of these tension load-bearing structures work together to maintain integrity of the longitudinal arch and increase the stiffness of the longitudinal arch to resist longitudinal arch flattening and lengthening during weightbearing activities. The central nervous system regulates the contractile activity of the active elements of the LALSS in order to regulate the stiffness of the longitudinal arch over and above the baseline longitudinal arch stiffness offered by the passive elements of the LALSS, the plantar ligaments and plantar fascia.

    I introduced the concept of the LALSS in my fourth book (Kirby KA:
    Foot and Lower Extremity Biomechanics IV: Precision Intricast Newsletters, 2009-2013. Precision Intricast, Inc., Payson, AZ, 2014). I also more recently explained the LALSS in regards to the plantar fascia in a recent article in Podiatry Today Magazine (Kirby KA: Understanding ten key biomechanical function of the plantar fascia. Podiatry Today, 29(7):62-71, 2016).

    http://www.podiatrytoday.com/understanding-ten-key-biomechanical-functions-plantar-fascia

    To think that the thin-walled veins of the plantar arch musculature have anything significant to do with the mechanical ability of the longitudinal arch to maintain its passive stiffness or with the central nervous system to vary the stiffness of the longitudinal arch during weightbearing activities seems highly unlikely, if not ludicrous.
     
  15. scotfoot

    scotfoot Active Member

    "To think that the thin-walled veins of the plantar arch musculature have anything significant to do with the mechanical ability of the longitudinal arch to maintain its passive stiffness or with the central nervous system to vary the stiffness of the longitudinal arch during weightbearing activities seems highly unlikely, if not ludicrous."



    I quite agree Kevin but have no idea were you got this from .
     
  16. scotfoot

    scotfoot Active Member

    "The idea that the plantar venous plexus (PVP) of the plantar intrinsic muscles has anything to do with the structural integrity of the longitudinal arch of the foot is improbable at best. I am very familiar with Luke Kelly, PhD's excellent research on plantar intrinsic muscles. In fact, both Dr. Kelly and I will be lecturing on plantar intrinsic muscle function at the Biomechanics Summer School in Manchester, UK, in June 2017."

    " To think that the thin-walled veins of the plantar arch musculature have anything significant to do with the mechanical ability of the longitudinal arch to maintain its passive stiffness or with the central nervous system to vary the stiffness of the longitudinal arch during weightbearing activities seems highly unlikely, if not ludicrous."

    Hi Kevin
    Above are two quotes from your most recent post on this thread . I have tried to puzzle out how you got from my text to your stated interpretation of the text but remain baffled .

    My idea is that the vessels of the plantar venous plexus collapse under transverse loading of the plantar intrinsics and so help to expel blood from the foot . If the vessels are collapsing they are not supporting .

    Baffled .

    Regards

    Gerry
     
  17. Gerry:

    I thought you were saying that the plantar veins somehow helped support the longitudinal arch of the foot when you said:

    "So the question for me is -Is there an increase in the intra and inter muscular pressure in early stance and can this be attributed to PTC ?
    An in vivo study to investigate this might involve indwelling intramuscular pressure sensors but why go down this road when such a sensor may already be in place in the form of plantar venous plexus (PVP).
    So can the PVP be looked at in this way? Is the pump emptied by inter-muscular pressure or by stretching and necking down ?
    NECKING DOWN-
    Since the veins of the plexus are elastic longitudinally and viscoelastic transversely the effective emptying of the PVP by stretching and necking down is ,in my inexpert view ,unlikely .
    So if necking down is not the mechanism of PVP emptying then the pump must be emptied by increased inter- muscular pressure .But what cases this ?
    If the pump empties in early stance when the plantar intrinsic muscles are not activated then the pressure must be created by stretching of the PIFM or by PTC.
    A study by BJ Broderick et al(1)showed that the PVP is emptied when a standing individual performs toe curls so it can be inferred that inter-muscular pressure is increased when the muscles become activated and contract. I believe that it is reasonable to think that inter-muscular pressure is therefore not increased when the same muscles become less active and return to their original more lengthened positions .
    So, in my opinion, it is most likely that in early stance the PVP is emptied by the passive transverse compression of the “intrinsic core” and indeed that the existence of a functioning PVP confirms the existence of a significant level of PTC . I also think it likely that the pressure generated in the pump reflects the inter and intra-muscular pressures generated within the “intrinsic core” and hence the pressures generated at the interfaces between the core and the plantar fascia and BA ."

    and ...

    "After considering the mechanisms outlined in the extracts above it seemed to me that if the intrinsics were to be the compressible and thus supportive core of the foot then the muscles and constituent fascicles making up this core must be able to apply force at their points of insertion without power loss through work partitioning . This is were the theory of hydraulically discrete fascicles came from."

    If that is not what you were saying, then I'm sorry I didn't understand what you wrote.
     
  18. As I recall, Bojsen-Moller talked about the orientation of blood vessels in the heel and described how the compression of the heel pad at initial contact played a role in venous return.
     
  19. scotfoot

    scotfoot Active Member

    Hi Kevin
    It has to be said the misunderstanding occurred with regard to a theory ,within a theory explained by another theory.

    Regards
    Gerry
     
  20. scotfoot

    scotfoot Active Member

    Hi Kevin
    Could I ask what your opinions are regarding the mechanism by which the contents of the plantar venous plexus are emptied into the posterior tibial veins during weight bearing ? My understanding is that the pressure generated is enough to move a column of blood up the body and into the right atrium . That's a lot of pressure .
    Regards
    Gerry
     
  21. Gerry:
    Gerry:

    Here is what I do know about the veins of the foot and lower extremity from my animal physiology major and exercise physiology background during my undergraduate years at U.C. Davis. Heart and circulatory physiology were courses I needed to take in my major which was again reemphasized in the graduate courses I took in exercise physiology at UCD.

    First of all, veins are relatively low-pressure, thin-walled tubes which have much more compliant vessel walls than the higher-pressure, thicker-walled and stiffer arteries. As such, in order for deoxygenated blood to travel against gravity from the foot back to the heart at the relatively low pressures within the venous system, the veins of the foot and lower extremity have specialized valves along the venous return path to the heart to shorten the distance that blood will need to travel in this low-pressure system from one valve to another. Venous valves are "one-way valves" meaning that fluid pressure acting on the valve leaflets in the proper flow direction will easily open the valves to allow the flow of blood back toward the heart. However, venous fluid pressure acting in the improper flow direction (i.e. back toward the foot) on the valve leaflets will encounter high resistance from the valve leaflets that greatly helps prevent venous blood flow back towards the foot.

    Secondly, the venous system of the foot and lower extremity, due to it's system of valves, does not need to rely on high pressures to "pump" blood back to the heart. All that needs to occur for blood to return from the foot back to the heart is for the foot and lower extremity muscles to collapse these thin-walled, compliant vessels and push a small amount of blood within each vein from one valve to another along the venous path back toward the heart. In other words, we don't need to have our foot muscles create such high pressures within the veins that it can generate enough intravenous pressure to shoot blood up the four-foot-high fluid column all the way to the heart. This is not needed due to the elegant venous valve system in our feet and lower extremities. Also, having a high pressure venous system in our feet would be harmful since intravenous pressures of this magnitude at the foot level would literally blow out or rupture the thin-walled veins which were not designed to accept such large fluid pressure heads.

    Therefore, in answer to your question, I do believe that the plantar intrinsic muscles of the foot can generate some increase in pressure on the plantar venous plexus to collapse their vein walls and push venous blood through the posterior tibial veins up the leg toward the heart, from one valve to another. However, my guess is that the highest column of venous blood that the plantar intrinsic muscles could push the venous blood up the leg would only be to the distal tibial level, and not higher, due to the relative compliance of the posterior tibial veins. [As an aside, when I do tarsal tunnel release surgeries and touch the posterior tibial veins lightly with a blunt instrument, their vein walls are very flexible and compliant and certainly were never meant to have large fluid pressure columns acting on them.] In other words, I would find it extremely unlikely and against the physics of hydrodynamics that "the pressure generated" in the plantar venous plexus by the plantar intrinsics "is enough to move a column of blood up the body and into the right atrium".

    Hope this answers your questions.
     
  22. scotfoot

    scotfoot Active Member

    Hi Kevin
    Re the pressures generated by the plantar venous plexus my information comes in part from the paper referenced below . The passage in this paper of most relevance is as follows ------

    " Passive weight bearing flattens the plantar arch, stretching the veins longitudinally, causing them to constrict 'neck down' and dislocate the blood with sufficient force to overcome the resistance of a sphygmomanometer cuff inflated to over 100 mm around the calf. This alone is adequate to return blood from the foot to the right atrium in the upright position. The foot pump has been shown to be functional in paraplegic legs."

    Regards
    Gerry

    Ref Annals ofthe Rheumatic Diseases 1992; 51: 1173-1178 The venous footpump: influence on tissue perfusion and prevention of venous thrombosis A M N Gardner, R H Fox

    Link to full text of ref -


    The venous footpump: influence on tissue perfusion and prevention of ...

    ard.bmj.com/content/51/10/1173.full.pdf
    by AM Gardner - ‎1992 - ‎Cited by 39 - ‎Related articles
     
  23. Gerry:

    Passive weightbearing also causes the gastrocnemius and soleus to exert contractile activity which will also exert a collapsing force on the veins of the leg and/or increase the stiffness of the vein walls. I wouldn't be so certain that all the "pumping action" of pushing the blood up past a sphygmomanometer inflated to 100 mm Hg at the level of the calf is all coming from some sort of "venous foot pump". Rather, I would think that the "venous calf pump" is much more powerful than any "venous foot pump" and also, due to larger diameter of veins in the leg than in the feet, the "venous calf pump" probably has a much better ability (i.e. larger capacity or volume) to push larger volumes of blood past a sphygmomanometer inflated to 100 mm Hg at the calf.

    In addition, Gerry, before you get too excited about this "venous foot pump" that the authors claim to exist, you may want to read the names on this patent of the medical device in the article you linked. The authors of the paper and the inventors of the device mentioned in the paper are the same. No big surprise here. Unfortunately, this paper was published at a time when authors were not required to list financial interests in products mentioned in their papers. Reader beware!

    https://www.google.com/patents/US5634889
     
  24. scotfoot

    scotfoot Active Member

    Hi Kevin
    In post 21 of this thread you said " , I do believe that the plantar intrinsic muscles of the foot can generate some increase in pressure on the plantar venous plexus to collapse their vein walls and push venous blood through the posterior tibial veins up the leg toward the heart, from one valve to another. "

    May I ask by what mechanism you believe the plantar intrinsic muscles act to cause "the plantar venous plexus to collapse their vein walls and push venous blood through the posterior tibial veins "?
    I believe it is via transverse compression of the eccentrically contracting ,lengthening plantar intrinsics in early stance and can see no other plausible explanation .

    Regards
    Gerry
     
  25. Gerry:

    I don't really know. However, I do know that in all other parts of the body, muscle contraction helps pump venous blood without necessarily lengthening the veins.
     
  26. scotfoot

    scotfoot Active Member

    Could I recommend this thread to any groups studying foot energetics and considering publishing material on the characteristics of the intrinsic foot muscles under compression . Perhaps , if it is appropriate , it might even be referenced .
     
  27. efuller

    efuller MVP

    Are you asking for permission? I don't think there was consensus on this thread so you could reference this thread if you wanted to claim there is debate on the topic. It is not appropriate to cite your own opinion as a reference.
     
  28. scotfoot

    scotfoot Active Member

    Eric ,
    Your post makes little sense to me . However , your contribution to this particular thread is of no importance to originality , that I can see , so with that in mind I will repost the material minus the input of others and recommend that post as a potential point of reference to those how might have an interest .

    Just looking for a fair shake
     
    Last edited: Aug 21, 2018
  29. efuller

    efuller MVP


    Gerry, what do you mean by referenced? Do you mean referenced in the sense of here is where to look for support of my ideas. Or do you mean here is where to look for a longer explanation of my ideas. If the latter, it would be much better for your readers to condense your thoughts rather than refer to an entire thread.


    Gerry, How do you feel you have not been given a fair shake?

    Also, why do feel the need to repost this information?

    If you want to reference (as in here is support for my ideas) your ideas, you should write a paper and submit it to a journal where your ideas can be peer reviewed.
     
  30. scotfoot

    scotfoot Active Member

    Hi Eric
    You wrote -
    "If you want to reference (as in here is support for my ideas) your ideas, you should write a paper and submit it to a journal where your ideas can be peer reviewed. "

    My understanding is now that material from blog sites can be referenced in academic papers .

    If you develop a theory and back this with logic and appropriate references then you have something called "founded theory " . If , subsequent to publication on this site ( and if you post here you have published ) , a group presents material to another publisher for peer review that looks to have some very similar content to your own , then some form of reference to your work from the group going through the more formal route , might be a good idea .
     
  31. scotfoot

    scotfoot Active Member

    Above , " founded theory " should read "grounded theory" .
     
  32. efuller

    efuller MVP

    The key here is appropriate references. It may be ok to cite a blog post, but the content of the blog should support your idea. For example, if you developed a theory and then posted it on a blog. It would be inappropriate to cite that blog in support of your theory. Especially, if you were the only one to post on that blog, or if there was disagreement on the validity of the theory on that blog. In the latter case, you could cite that there is disagreement on the theory, but you could not appropriately cite the blog as support for your theory. Repeating something multiple times, does not make it true.

    I agree that a theory can be supported with logic and appropriate references.
     
  33. scotfoot

    scotfoot Active Member

    Hi Eric
    I see were you are coming from but the reason I sometimes post old material of my own is to do with the time line and not the reinforcement of points . That is ,the time and date when I first said something is important to me if I believe it to be novel and likely to eventually be taken up by others .

    For example I once wrote some material on a site called OESH shoes . I spent a considerable amount of time thinking about the material and much of it was novel .On the site , the date and time of posting was recorded . One day I looked for the material and it was gone . I thought "well fair enough it's their site" , and since I had screen saved the material I was able to look for somewhere safe park it . Here .

    I also feel that , sometimes on Pod arena , the conversations produce novel material , which may influence reading academics . If those influences then affect the content of a subsequent paper , might the academic cite Pod Arena if they choose ?

    ( Please note that I am not talking about any particular academic or group of academics in this post , but rather academics in general . )
     
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