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The foot as an organ of circulation

Discussion in 'General Issues and Discussion Forum' started by scotfoot, Mar 14, 2021.

  1. scotfoot

    scotfoot Well-Known Member


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    In my opinion the entire foot is an osseofascial pump, critical to venous return from the foot and lower limb .
    Backing this assertion are these images from AMN Gardner and RH Fox . Note that weight bearing empties both the superficial and deep venous systems ( long sapheneous and plantar venous plexus ) .

    During weight bearing the foot changes shape . As the bones of the foot flatten and the fascia is put under tension , the tissues located between the enveloping fascia of the foot and the bony arch are compressed and this powers coordinated venous return .
    This system is not reliant on the heel ever touching the ground .

    What other complete explanation is there for the images below ?

    upload_2021-3-14_8-56-54.jpeg
     
  2. scotfoot

    scotfoot Well-Known Member

    If changes in foot shape power the osseofascial foot pump ,what happens to venous return ,through the deep and superficial systems , when change of shape is prevented / impeded ? For example tight footwear ,high heels or even taping .
     
  3. scotfoot

    scotfoot Well-Known Member

    Take the example of taping from above . Now I am not talking here about the sort of taping that might be applied for plantar fasciitis /heel pain but rather something all together more restrictive .

    It would be fascinating to see a study conducted into venous return from the foot where an individual walked first barefoot and then in a foot fairly tightly bound with zinc oxide tape . I have a strong suspicion that if the foot is prevented from flattening transversely and longitudinally during early stance then venous and lymphatic return from the lower limb will likely be impeded .
    Please note that I am not suggesting anyone binds there own or anyone else's foot without qualified supervision and in a controlled setting .

    If venous and lymphatic return are impeded when changes in foot shape are impeded, then that opens up interesting areas of study .
     
  4. scotfoot

    scotfoot Well-Known Member

    On the dorsal aspect of the foot , and speaking very generally, we have the dorsal venous arch giving rise to the greater and lesser saphenous veins . On the plantar aspect of the foot we have the vessels of the plantar venous plexus ,and then we have perforator veins which allow communication between these two systems . That is to say venous blood is able to flow from the plantar vessels to the dorsal .

    The existence of a plantar foot pump has been recognized for some time and this is activated by weight bearing, moving blood into the posterior tibial veins . But what is to stop blood flowing from the pressurized plantar plexus, not into the posterior tibial veins ,but into the dorsal venous system via the perforator veins ,thus reducing the effectiveness of the plantar venous pump .

    The answer, I believe , lies in the fact that the whole foot is an osseofascial pump and that at the same time as the plantar veins are being pressurized so are the dorsal veins .

    During weight bearing the bony arch of the foot deforms transversely and longitudinally . This deformation is resisted by the enveloping fascia's of the foot creating pressure in the vessels which lie between the two . Transverse deformation in particular powers the dorsal aspect of venous drainage . The plantar aspect is powered by compression of the intrinsic foot muscles btwn the bony arch of the foot and the plantar fascia . The heel of the foot need never touch the ground during gait for this osseofascial system to function .
     
  5. scotfoot

    scotfoot Well-Known Member

    Here is a link to an 8 second video of a very simple model ,made at no expense , which demonstrates how change in foot shape, resisted by the foots fascia's, can help move blood out of the veins of the plantar aspect of the foot and back towards the heart.

    The cardboard represents the bony arch of the foot ,the plastic wrapped around the cardboard represents the foot's fascias ,and the glove finger filled with shaving cream, represents a blood filled vein . All very simple ,but not ,I think, in the literature .

    See again figures A and B in post #1 .

     
  6. scotfoot

    scotfoot Well-Known Member

    Worth noting .
    The stroke volume of the human heart ,that is the amount of blood pumped out from the left ventricle and around the body with each heartbeat , is about 70ml . The amount of blood moved out of the foot with each step is 20-30 ml from the plantar veins alone ,and this with enough pressure to lift a column of blood all the way to the heart .
     
  7. scotfoot

    scotfoot Well-Known Member

    With regard to the initial windlass phase of gait, I wonder if one of the benefits of dorsiflexion of the toes prior to foot strike might be connected with increased stroke volume during weight bearing . (As stated above it is important to note that the stroke volume of the heart is 70ml and the stroke volume of the plantar venous plexus of the foot alone, is 20-30ml with every step .)

    I introduced the idea that the whole foot is a gravity driven blood pump some time ago on podiatry arena ,and by that I mean that during weight acceptance ,changes in skeletal foot shape are resisted by the fascias of the foot in concert with compression/distortion of the other tissues of the foot, particularly the intrinsic foot muscle mass . (see link to video )

    If, prior to foot strike, the toes dorsiflex, giving rise to closer approximation of the heel and forefoot and creating more volume between the plantar fascia and the bony arch of the foot, then this might make it easier for the vessels of the superficial and deep venous systems to fill with blood giving an eventual increased stroke volume .

    It seems to me, that during gait especially, the importance of the foot as a circulatory pump may be greatly underestimated .

     
  8. scotfoot

    scotfoot Well-Known Member

    It seems quite clear to me that the feet have a key role to play in circulation and may even be viewed, in their entirety,
    as blood pumps .
    Why does this matter ? Back in Feb 2019 I had a conversation, on a site called Biomch-l ,with Professor Ton van den Bogert about the effects of centrifugal forces on venous return from the lower limb . As best I can make out, the centrifugal effect on venous return had never been considered before, but the conclusion I have reached is that it should be . Blood flow out of the lower limb is not just about overcoming gravity .

    With Prof Bogarts permission, here is part of the thread from the biomch-l site . Note that "centripedal " should read "centrifugal" .


    • Centripedal forces and the calf muscle pump

      February 7th, 2019, 05:56 AM
      You will be aware of the foot pump and the calf muscle pump and you might well have read texts which describe their function . In every text I have ever read the calf pump in particular is described as helping to move blood towards the heart against gravity . However what about the centripedal forces and centrifugal effect generated in the legs and vasculature during walking and running . I have never ,in years of looking ,found a paper on venous return which takes these forces into account when ,for example ,discussing venous reflux .

      Surely these forces are increasing relevant as you move from slow walking to brisk walking to jogging then running then sprinting .

      It is worth noting that in individuals with previous heart failure and thus reduce cardiac capacity , poor venous return may reduce preloading (Starling mechanism ) and thus cardiac output .

      What do you think . Have the vascular people missed a trick ?

      Gerry
      Last edited by Gerrard Farrell; February 9th, 2019, 07:23 AM. Reason: spelling
      Tags: calf muscle pump, plantar foot pump
    • [​IMG]
      Gerrard Farrell[Gerrard Farrell]
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      #2
      February 7th, 2019, 02:25 PM
      Re: Centripedal forces and the calf muscle pump

      Here is an abstract of a very recent paper which looks a calf muscle pump function (below) .

      Pump function is looked at under 3 conditions but none replicate the additional centripetal forces encountered during gait .

      I am not a physicist but as close as I can roughly calculate , if an individual is running at 3m/s with a hip joint to plantar foot length of 1m ,then ,if they also have very little leg lift ,venous blood in the foot is effectively subject to 2Gs . There will be a reduction in centripetal forces and "centrifugal effect" the further distally you move along the leg .

      Is this not significant ?

      Ton ,as the "physicist in residence" as it were, can you help with this at all ?

      Cheers

      Gerry

      Phlebology. 2018 Jun;33(5):353-360. doi: 10.1177/0268355517709410. Epub 2017 May 22.
      Optimizing calf muscle pump function.

      Lattimer CR1,2,3, Franceschi C4, Kalodiki E1,2,3.
      Author information



      Abstract

      Background The tip toe manoeuvre has been promoted as the gold standard plethysmography test for measuringcalf muscle pump function. The aim was to compare the tip toe manoeuvre, dorsiflexion manoeuvre and a body weight transfer manoeuvre using the ejection fraction of air-plethysmography and evaluate which has the best pumping effect. Methods Sixty-six archived tracings on 22 legs were retrieved from an air-plethysmography workshop and analysed. Pumping performance was measured using the calf volume reduction after each manoeuvre. Results Expressed as median [inter-quartile range], body weight transfer manoeuvres resulted in a significantly greater ejection fraction (%) than tip toe manoeuvres at 59.7 [53.5-63.9] versus 42.6 [30.5-52.6], P < 0.0005 (Wilcoxon). There was no significant difference in the ejection fraction between the tip toe manoeuvre versus dorsiflexion manoeuvre, P = 0.615. The repeatability (confidence interval: 95%) of 66 ejection fraction tests was excellent: tip toe manoeuvre (±1.2), dorsiflexion manoeuvre (±1.3) and body weight transfer manoeuvre (±1.6). Conclusion The body weight transfer manoeuvre appears to be a better method of measuring the full potential of the calf muscle pump with a 40.1% relative increase in the ejection fraction compared to a tip toe manoeuvre. Exercises which involve body weight transfers from one leg to the other may be more important inoptimizing calf muscle pump function than ankle movement exercises.

      Last edited by Gerrard Farrell; February 9th, 2019, 07:25 AM.
    • [​IMG]
      Ton van den Bogert[bogert]
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      #3
      February 7th, 2019, 02:58 PM
      Re: Centripedal forces and the calf muscle pump

      Let's try to put some numbers on this effect.

      The centrifugal effect would be largest during sprinting, where the swing time is about 1/3 s and the leg may swing through a 90 degree arc [1]. That corresponds to an angular velocity of 270 degrees/s or 4.5 radians/s.

      The radius of the arc is probably 0.7 m or so. This gives you a centrifugal effect of 4.5^2 * 0.7 = 14 m/s^2.

      This seems significant, more than doubling the effect of normal gravity.

      However, don't forget there are flight phases during sprinting, during which the body is in free fall, and the effect of gravity is zero. The flight phases are as long as the stance phases [2]. During those flight phases, the venous return will be much easier.

      This may well be the reason why the heartbeat and gait cycle become coupled during running [3]. Kirby's graphs suggest that systole (with peak flow rate following the ECG pulse) occurs just before heel strike, when the body is in free fall.

      Ton van den Bogert

      References:
      [1] Thelen DG, Chumanov ES, Hoerth DM, et al. Hamstring muscle kinematics during treadmill sprinting. Med Sci Sports Exerc. 2005;37(1):108–114.
      [2] Morin, Jean-Benoît et al. “Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production” Frontiers in physiology vol. 6 404. 24 Dec. 2015, doi:10.3389/fphys.2015.00404
      [3] Kirby R.L., Nugent S.T., Marlow R.W., MacLeod D.A., Marble A.E. (1989) Coupling of cardiac and locomotor rhythms. Journal of Applied Physiology 66, 323-329.
    • [​IMG]
      Gerrard Farrell[Gerrard Farrell]
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      #4
      February 8th, 2019, 07:43 AM
      Re: Centripedal forces and the calf muscle pump

      Many thanks for the above .

      During gait on a running track ,the foot undergoes periods of rapid acceleration ,even more rapid deceleration and not moving at all if we take the track as a reference point .

      For example let's say we take an individual walking at 1.5 m /s . That is to say the persons COM is moving at 1.5 m/s relative to the track . The standing leg (reference leg )will be on the track and not moving at all so we have a "velocity gradient" along the length of the leg as the body moves forwards .

      So now let's say the swing foot touches down on the track and the reference foot starts to clears the track .
      The reference foot was moving at 0m/s but must quickly accelerate to catch and pass the body . So let's say it goes from zero to 3m/s in a third of a second . This acceleration of the reference leg and foot is likely to generate substantial centripedal forces and centrifugal affect making venous return more difficult than if it were merely against gravity .

      So the reference foot now comes past the body and just as it touches the ground , it decelerates very rapidly to zero ,and then to 1.5 m/s in the opposite direction to the COM so again we have higher centripedal effect .

      I don't have the maths to work this all out so resorted a bottle of HP sauce strapped to my ankle .

      . In a quite part of Glasgow I then walked a number of steps and found that the thick sauce did indeed flow much more rapidly out of the bottle during the swing phase of gait and at the end of the swing phase in particular ,as the foot rapidly decelerates . (It should be noted that even although the now track bound foot is not moving relative to the track it is moving at 1.5m/s relative to the body and so centripedal forces are still being generated )

      I do not recommend this experiment at all as it causes a real mess ,there is a danger of slipping on the sauce and my training shoes are now in the bin .

      Ton , could you once again put some figures on the above ? It may be that the way venous return is viewed needs to be changed .

      Gerry
      Last edited by Gerrard Farrell; February 8th, 2019, 07:56 AM.
    • [​IMG]
      Ton van den Bogert[bogert]
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      #5
      February 8th, 2019, 05:01 PM
      Re: Centripedal forces and the calf muscle pump

      I love how you used a bottle of HP sauce as an accelerometer. You can actually use a smartphone for this purpose, there are apps that can log the accelerometer signals.

      A friendly spelling correction, it is "centripetal", and I would probably not even use that word, but just talk about the centrifugal effect. We're not interested in the tensile (centripetal) force that prevents your foot from flying off. We're interested in the (pseudo-) force that influences blood flow.

      The deceleration of the leg is certainly highest during heel strike, and your sauce probably flows fastest at those times.

      Now, at the same time that the venous return is inhibited by centrifugal or impact effects, the arterial flow (which is downward) would be assisted, and help push blood into the veins from below. So you might question whether overall there is a hindrance of venous return.

      From anatomy labs, I remember that veins have a larger cross section than arteries, so more blood mass in the veins, so I suspect you are still correct about venous return being hindered by centrifugal and impact effects.

      I found Kirby's paper quite interesting but I don't have the time or expertise to go further into this topic. Perhaps there is an exercise physiologist who can comment.

      Ton
    • [​IMG]
      Gerrard Farrell[Gerrard Farrell]
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      #6
      February 9th, 2019, 06:44 AM
      Re: Centripedal forces and the calf muscle pump

      Many thanks Ton .

      Re the repeated and slightly embarrassing spelling error ( I am too old to be very embarrassed ) , could I pass that off as the result of a speech impediment suffered by my former school physics teacher ?

      Gerry
      Last edited by Gerrard Farrell; February 9th, 2019, 08:12 AM.
     
  9. scotfoot

    scotfoot Well-Known Member

    For a number of reasons I feel it is important to realise that the osseofascial pump, which is the foot, is primarily activated by changes in the skeletal shape of the foot ,resisted by the fascia and other soft tissues, which occurs during weightbearing .
    The plantar venous plexus and superficial systems are not emptied by stretching and necking down or, primarily, by muscular contraction .

    Again from Biomch-l, here is an explanation of this -
    Venous foot pump
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      [​IMG]
      Gerrard Farrell[Gerrard Farrell]
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      #1
      Venous foot pump

      February 21st, 2019, 06:37 AM
      I read somewhere that the venous foot pump can be viewed as priming the calf pump in a fashion that resembles the atria priming the ventricles .

      With regard to how the foot pump functions , the idea that the vessels of the plantar venous plexus are stretched during weight bearing , and that this stretching empties them , still persists . I believe that this idea is demonstrably wrong .

      An article published in 2012 ,E Lindsay et al ,(see below ) lays out the argument for a vessel stretch mechanism very well .

      Here are 2 quotes from the article -

      1 When weight is applied to the sole of the foot, the plantar arch is flattened. The resulting longitudinal stretching of the veins allows the blood to be pumped along the long and short saphenous veins into the deep calf veins, even when the patient is in the upright position.

      2 Gardner and Fox also found that ‘weight bearing on a flaccid hemiplegic leg with the knee locked also caused flow in the femoral vein’, indicating that the foot pump may be functional in paraplegic legs. It has also been suggested that stretching the arch without weight bearing may be sufficient to empty the veins (Gardner and Fox, 1983).

      The problem with the stretch to empty theory is that veins are viscoelastic and stretching them will not effectively empty them .

      Here is a simple experiment that is even cheaper than my previous HP sauce efforts .
      I filled a simple latex glove with cold water . Then I got someone to hold the fingers whilst I pulled up on the open end of said glove to stretch it . Far from the glove emptying ,more room was created for addition water .

      I was pretty certain of what would happen before I started but thought I would check anyway .

      Any thoughts ?


      Short-stretch compression bandages and the foot pump - Nursing Times

      https://www.nursingtimes.net/.../030624Short-stretch-compression-bandages-and-the-f...




      by E Lindsay - ‎Cited by 2 - ‎Related articles
      9 Nov 2012 - leg, focusing on calf-muscle function and the action of the foot pump. They discovered that the plantar venous plexus fills when the foot is ..
      Tags: plantar venous plexus, venous foot pump
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      Dan Robbins[drobbins99]
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    #2
    February 22nd, 2019, 05:19 AM
    Re: Venous foot pump

    Hi Gerrard,

    One of the major issues with the sauce and glove experiments you describe is the lack of valves. In human leg the valves prevent the pooling (which is the effect you are seeing in the open glove).

    (The above is an extract from another contributor, shortened for copyright reasons .)
    • [​IMG]
      Gerrard Farrell[Gerrard Farrell]
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    #3
    February 22nd, 2019, 03:25 PM
    Re: Venous foot pump

    Hi Dan
    Taking the second part of your reply first , I have to say I agree that more advanced studies into certain aspects of venous return ( centrifugal effects ) in the lower limb are required than can be provided by a bottle of sauce .

    With regard to the glove experiment as a means of demonstrating that stretching out veins does not make for an effective pump , I feel something that simple is really all that is required .

    But let's say you take a length of vein , valves and all ,fill it with blood and tie off the bottom end . Now hold the vein upright and stretch .Yes the circumference will decrease but the length will increase giving little change in volume and a very ineffective pump .
    You mentioned Bernoulli's principle ,above , but that is about the conservation of energy whilst the foot pump is all about generating energy .

    The main people in the foot pump story are AMN Garder and RH Fox ( although many others have played a role before and since ) . They wrote " We have discovered a venous pump mechanism in the sole of the human foot that is able to return blood from the leg up into the abdomen with no assistance from muscular action " . And to a certain extent they had . It just that ,in my opinion , they misunderstood the mechanism by which their pump worked .

    They carried out a series of experiment including introducing a contrast medium into the deep plantar veins . Toe flexing did not move the contrast medium out of the veins but weight bearing did so the pump does not work by muscular contraction alone .

    How does this powerful pump work ?
    In my opinion ,during weight bearing , the bony arch of the foot lowers and the plantar fascia , which is continuous between medial and lateral aspects of the foot ,is stretched . The muscles between the two elements are subject to a volume which is trying to reduce ,and this results in increased intermuscluar pressure .

    This powers the foot pump . No muscle to compress means a far less effective pump . Muscle with some tone will produce a more effective pump etc

    Gerry
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      Gerrard Farrell[Gerrard Farrell]
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    #4
    February 23rd, 2019, 06:58 AM
    Re: Venous foot pump

    A very interesting paper was just published by the Karl Zelik lab on soft tissue work during early gait (see below ) . Such soft tissue work would include the deformation of the heel pad and compression / distortion of the other tissues of the foot .

    It seems to me that the compression of the tissues that lie between the bony arch of the foot and the plantar fascia would also play a large role in the soft tissue work done by the foot .
    If that is indeed the case then one might expect to see a lower contribution from this source when walking uphill but a higher , and later contribution when walking downhill (foot slapping action ) .

    I would be very interested to hear what Karl and Eric think of the above .

    Gerry

    Paper Foot and shoe responsible for majority of soft tissue work in early ...

    https://www.ncbi.nlm.nih.gov/pubmed/30769210

    by EC Honert - ‎2019
    12 Feb 2019 - Foot and shoe responsible for majority of soft tissue work in early stance of walking. Honert EC(1), Zelik KE(2). Author information: (1)Dept. of ...
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      Gerrard Farrell[Gerrard Farrell]
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      #5
      February 28th, 2019, 02:37 PM
      Re: Venous foot pump

      Anyone who might have read my last few posts will be aware that my experimental equipment consists of a half empty bottle of HP sauce and a water filled surgical glove . This is more of the same !

      The post above mentions a paper , very recently published by Hornet and Zelik , which looks at soft tissue work in the early stance of walking .

      The post also raises the question of whether the tissues between the bony arch of the foot and the plantar fascia are compressed during gait and so contribute to soft tissue work .

      So let's take the surgical glove, adapt it ,and use it to demonstrate tissue compression between the bony arch and the foot .

      Take the glove ,empty it of water and tie off the fingers . Now turn it inside out and fill it again with water . Now tie off the top of the glove so that you have a small water filled sphere .
      Next , place your cupped hand ,palm down , on a table . The lateral border of the hand lies flat on the table but the medial aspect will form an arch analogous to the medial arch of the foot .

      Now place the water filled sphere under the arch /cupped hand , then press down to represent the lowering of the bony arch of the foot during weight acceptance during gait . You will notice that the sphere is compressed between the hand and the table (analogous to the plantar fascia ) and so it bulges inwards . Now place your free hand so that it stops the water filled sphere from bulging inwards ( this hand represents the medial part of the plantar fascia ) .You can appreciate how the water trapped in the glove is now pressurized as the cupped hand is pressed down .

      Note ; in the case of the foot this system will not prevent the foot from pronating as the bony arch and the fascia will lower towards the ground as part of the same unit . Instead the intrinsics will act as
      (1) a pressurized core reducing shear forces between the components of the bony arch
      (2) an energy sump (soft tissue work )
      (3) a pump for moving blood out of the plantar venous plexus


      The intrinsic can of course do all of the above whilst at the same time acting to shorten the foot or reduce pronation , if they contract with sufficient force . The mechanism by which these muscles can contract whilst under transverse pressure is explained in this thread .(below )

      Any thoughts ?

      Hydraulically discrete fascicles in skeletal muscle [Archive ...



      https://biomch-l.isbweb.org/archive/...p/t-28655.html




      13 Feb 2016 - 2 posts - ‎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 ...
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      Gerrard Farrell[Gerrard Farrell]
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      #6
      March 4th, 2019, 02:00 PM
      Re: Venous foot pump

      The WHOLE FOOT is a pump ! ( almost )

      After a lot of reading on the subject it is starting to look to me like almost the entire foot is an "osseofascial pump " dependent for its power on the changing shape of the osseous components of the foot during weight acceptance .

      As weight is accepted onto the reference foot during gait , the medial and lateral longitudinal arches and the transverse arch are compressed , leading to increased tension in the interconnected deep and superficial fascial structures that envelop the foot . This increase in tension causes compression of the soft tissues of the foot including most of the venous system , dorsal and plantar .

      Fox and Gardner produce interesting before and after pictures of the coupled drainage of the dorsal and deep plantar venous components of the foot , see below. ( Note the almost total expulsion of blood from the venous components of the foot between the weight bearing and none weight bearing conditions) . The fascially related , coupled drainage of the plantar and dorsal aspects of the foot mean that perforator veins need not have valves .

      On the plantar aspect of the foot ,when the bony arch of the foot is compressed and the fascia stretched ,the muscular tissues between the two are compressed and this force is transmitted to the plantar veins causing them to empty . However , Fox and Gardner found that the plantar foot pump (in my opinion one part of a greater whole ) could operate in less effective fashion in the paraplegic foot , presumably because the fatty infiltrate that replaces much of the plantar intrinsic musculature in such feet is a less effective transmitter of force . But it did still function .


      The pressure generated by the foot , an osseofascial pump , increases with increased ground reaction forces allowing venous return from the foot to be maintained as centrifugal effects increase .

      The venous pump of the human foot--preliminary report. - NCBI

      https://www.ncbi.nlm.nih.gov/pubmed/6616290
      by AM Gardner - ‎1983 - ‎Cited by 169 - ‎Related articlesBristol Med Chir J. 1983 Jul;98(367):109-12. The venous pump of the human foot--preliminaryreport. Gardner AM, Fox RH. PMCID: PMC5077034.
      Last edited by Gerrard Farrell; April 26th, 2019, 02:10 PM. Reason: spelling
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      Gerrard Farrell[Gerrard Farrell]
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      #7
      March 7th, 2019, 08:08 AM
      Re: Venous foot pump

      Following some feedback ,the mechanism by which the whole foot becomes an osseofascial pump is not immediately apparent from the explanation I have given above , so this post is a bit of further explanation .

      Quote from above -

      "As weight is accepted onto the reference foot during gait , the medial and lateral longitudinal arches and the transverse arch are compressed , leading to increased tension in the interconnected deep and superficial fascial structures that envelop the foot . This increase in tension causes compression of the soft tissues of the foot including most of the venous system , dorsal and plantar ."

      A way of understanding this is as follows .

      Cup your hand as if you were trying to carry a little water in it or as if you were trying to cover a small egg on a table with your hand without crushing the egg . Maintain that hand shape as a friend puts a paper bag over the hand ,tightens the bag a litle to take up any slack and then tapes it in place with a few short pieces .

      So now you have something very roughly analagous to an arched foot enveloped in fascia . Now place your hand flat on a table top and push down on top of it with your other hand . As the hand (foot) flattens the paper bag becomes tensioned . The bag represents both the deep fascia and the superficial fascias of the foot

      In the foot the plantar fascia on the plantar aspect of the foot is continous with the fascia dorsals pedis . The superficial fascia is also continous going from plantar to dorsal .
      Last edited by Gerrard Farrell; April 26th, 2019, 02:12 PM. Reason: spelling
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      Gerrard Farrell[Gerrard Farrell]
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      #8
      March 11th, 2019, 07:10 AM
      Re: Venous foot pump

      TYING THE FOOT PUMP TO THE CENTRIFUGAL EFFECT .

      So for calculating angular acceleration (ac) we have ac = v x v/r This means that if an individual has a leg length of 0.7 m and is walking at 1.5 m/s then the angular acceleration is 3.2 m/s . Thus for the stance leg during gait the force acting on the column of blood at the ankle is not just gravity x mass , as has previously been the assumption but gravity plus angular acceleration giving a total force of about 13.2 x mass .

      Now , after toe off , the reference foot undergoes rapid acceleration , quickly reaching a velocity which allows it to catch and pass the body , so that it is in place for the next cycle . So let's say the reference foot reaches 3 m/s during the swing phase , so that gives an angular acceleration of (3x3) /.7 = 12.8m/s/s
      So the force applied to the venous valves at the ankle by the section of the column of blood immediately above is the mass of the blood x 22.8 ,not mass x 10

      That's a big difference compared to what was originally thought .

      What about running at say 3m/s ? During the swing phase that would give a foot velocity of about 6m/s . So angular acceleration = vxv/.7 = 51 m/s/s

      So for our section of the column of blood , that gives a force on the valves of mass x 60 . Not mass x ten (gravity only ).

      So with regard to venous return during gait , when you add the centrifugal effect into the equation ,in addition to gravity , you can see how vital the foot and calf pumps are .
     
  10. scotfoot

    scotfoot Well-Known Member

    Question : If toe dorsiflexion prior to foot strike helps prime the osseofascial foot pump by allowing the veins of the foot to better fill with blood ,then, would an a automated foot pump system benefit from incorporating toe dorsiflexion by, for example, mild electrical stimulation of the toe extensors prior to cuff inflation ? Interesting .
     
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