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Centripedal forces and the calf muscle pump

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    Still on the same general theme , is venous return from the lower limb easier to achieve in a tall individual with long legs or a smaller individual with proportionally shorter legs ? Intuition would say its more difficult with longer legs but this might not be the case in some instances .

    Let's say we take an imaginary couple where the man is six four and the woman is four ten . He has legs 85cm long and hers are 57 cm long .

    Now let's say they go out for a jog together and run at 3m/s . For the woman this would give a centrifugal effect at the ankle of 3x3/.57 =15.7 . Add in gravity and we have about 2.5 Gs acting on the blood in this section when the reference foot is on the ground . ( it would be much higher during the swing phase 6x6/.57=63 , so 7.3 Gs )

    For the man we have 3x3/.85 =10.58 , so about 2 Gs during stance phase . ( swing phase 42.3+ 10 giving 5.2 Gs - less chance of reflux than in the case of the woman's leg ? )

    Now the column of blood is longer in the male's leg , but is the higher centrifugal effect in the woman's lower leg enough to be the determining factor when considering the initial question " is venous return from the lower limb easier to achieve in a tall individual with long legs or a smaller individual with proportionally shorter legs ? "


    On a slightly different tack , cardio vascular fitness clearly involves not just the heart and lungs but the peripheral muscle pumps as well . So is peak cardiovascular fitness for swimming the same as that for running with regard to the peripheral pumps ? Probably not
    . Swim fit does not necessarily mean run fit for the cardiovascular system .

    Note ; the figure of 6m/s in the bracketed material comes from the parts of the swing phase just prior to ground contact and just after toe off but not the period between , when the velocity of the foot relative to the hip can be viewed as being back to about 3m/s . I got the 6 from looking at the foot relative to a static running track as a person runs down the track but in treadmill studies it represents the stance foot going from 3m/s backwards relative to the body to 3m/s forwards ,a transient velocity change of 6m/s (this bit might be wrong )

    . The centrifugal effect is generated by the foot/leg moving relative to the torso at the hip joint , so perhaps the best way to look more closely at the effect is by treadmill studies using markers and a bit of soft wear .
    Last edited by Gerrard Farrell; March 24, 2019, 04:54 AM. Reason: Note

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    Hi Joakim ,
    Many thanks for responding .

    Yes ,you are quite right , the question should say the upper end is hinged at a revolute joint (representing the hip joint) . The "acceleration " I mean relates to change in speed of the free end as it moving along its curved trajectory .

    Say you were sitting in a car going round a bend and the speedometer said a constant 30 miles an hour . The car would have constant angular acceleration .

    But what if you were going around the same corner whilst increasing speed from 30 mph to 60 mph (as measured by the speedo ) . How would you calculate the angular acceleration in that instance .

    Actually , I suppose you would be trying to find the rate of change in angular acceleration .

    But what does this mean for the force produced by the fishing weight (mass 100g ) on the seal .



    Gerry
    Last edited by Gerrard Farrell; March 11, 2019, 09:59 AM.

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  • Joakim Holmberg
    replied
    Re: Centripedal forces and the calf muscle pump

    Hello. I find this thread very interesting. Unfortunately I can't add much at this stage except perhaps answer your latest question if was reformulated somewhat. You ask:
    "If the upper end of the tube is fixed and the lower , sealed end of the tube accelerates at 30m/s/s ,what is the force in N placed on the seal by the fishing weight ?"
    Because the tube is assumed rigid with its "upper end" fixed the tube can't accelerate at all. Please describe the kinematics more clearly. For example, do you mean that the upper end of the tube is hinged (revolute joint)? And if so, do you mean that the total acceleration of the lower end is 30? In the (unlikely) trivial case that you mean a pure vertical motion of the tube then the normal force would be zero (since the fishing weight can't keep up, or down rather [pun intended]).
    /jokke

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    I am a bit stuck with some physics here and would greatly appreciate a bit of help .

    My understanding is that just after toe off , the foot is transiently accelerating at 30m/s/s .

    So let's say we have a leg 0.7 m long and let's represent that leg with a simple ,hollow ,rigid tube . Now the lower end of the tube is sealed off and this seal represents a venous valve . A mass of 100g , in the form of a fishing weight , is dropped into the tube to represent a column of blood resting on the valve .

    If the upper end of the tube is fixed and the lower , sealed end of the tube accelerates at 30m/s/s ,what is the force in N placed on the seal by the fishing weight ?

    I am familiar with the linear aspects of F=ma but have struggled to find an answer to the question posed above .
    Last edited by Gerrard Farrell; March 9, 2019, 08:12 AM.

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    External venous valves ( at least for the superficial system ) -


    " . If reflux is specific to a particular point in gait, for example just prior to the heel touching the ground ,then" external venous valves" might be possible which would prevent reflux being caused by the centrifugal effects generated during gait .

    The system would involve bands of electrically responsive material ,which could contract and relax in a rapid fashion , being placed around the leg at appropriate points along its length . The system might be controlled by an accelerometer worn around the ankle and even powered by materials which can produce electrical current by fabric movement . All the bits an pieces for such a system already exist . "

    Quote from Podiatry Arena made by me in response to a question .

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    In reply to a very reasonable point made earlier in the thread ( quote immediately below ) I have included two quotes from a recent paper ,S Magder et al 2016 (1) .


    QUOTE FROM THREAD

    "
    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."

    QUOTES FROM PAPER

    "A useful analogy for understanding the importance of the large compliance in veins and venules, and why the pressure produced by the heart is not important for the return of blood, is that of a bathtub [
    16]. The rate of emptying of a bathtub is dependent upon the height of water above the opening at the bottom of the tub. The height of water creates a hydrostatic pressure due to the mass of the water and the force of gravity on its mass, which pushes the water through the resistance draining the tub. However, the flow out of the tub is not affected by the pressure coming out of the tap."

    And

    "The same is true in the circulation. Arterial pressure flowing into veins and venules does not affect the flow out of the veins. "

    Link
    Volume and its relationship to cardiac output and venous return ...

    https://ccforum.biomedcentral.com/articles/10.1186/s13054-016-1438-7



    by S Magder - ‎2016 - ‎Cited by 44 - ‎Related articles
    10 Sep 2016 - Changes in cardiac output without changes in stressed volume occur because of changes in arterial and venous resistances which redistribute ...


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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    No need to apologize Adam , as the best threads often included twists and turns in subject matter .

    With regard to your very reasonable question -" In the paper you referenced, did they look at the calf muscle pump during gait? " then I would have to say that they did not .
    The foot and calf muscle pumps are generally viewed , by those active in this field of study , as being principally involved in countering the effects of gravity . Indeed , as far I am aware , this thread is the first time that the centrifugal effects generated during gait have ever been considered with regard to venous return .

    If that is indeed the case then it is both very surprising and encouraging . Encouraging because if venous reflux is related to a very specific point in gait , then better treatments can be developed than are currently available .

    Ideally , an expert in cardiovascular biomechanics might now make a contribution to the the thread . However , if I am correct in thinking that gait generated centrifugal effects have never been studied before in relation to venous return /reflux in the leg ,and perhaps never even considered , then such experts might not be queuing up to comment .

    Gerry
    Last edited by Gerrard Farrell; February 15, 2019, 02:15 PM.

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  • Adam Clansey
    replied
    Re: Centripedal forces and the calf muscle pump

    Hi Gerry,

    I apologize for going off topic, I probably should have started a new thread.

    Yes, sure I can give you my thoughts on this topic but just letting you know I am no expert in this area, so my thoughts are predominately based off intuition. ��

    I expect that there is a complex interaction between the large dynamic pressure gradient changes caused by skeletal muscle contractions (force-velocity-length relationship) that moves the leg (including the distal foot not just the calf/shank), and the centrifugal forces on venous return during locomotion. In addition, to the timing of the systolic and diastolic pressure during the gait cycle (as Ton pointed out). I think what would be interesting is to examine (and I don’t know if someone has) is the timing of when the peak centrifugal force occurs during running/sprinting, and the type of muscle contractions that occur in the leg (not just the calf musculature) to the venous return (blood volume). In the paper you referenced, did they look at the calf muscle pump during gait? Also, in the abstract of the paper, I noticed that they measured pumping performance by calf volume reduction. Is this an accurate measure of the calf muscle pump?

    Also, during gait the foot, shank and thigh rotate in opposite directions during the gait cycle so this dynamical system may have an important effect on venous return.

    Adam

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    If you start to consider the centrifugal effect on venous return , then perhaps it might be easier to better help with venous reflux during gait .

    For example , if as discussed above centrifugal effects are greatest as the foot rapidly decelerates during heel strike ,then might it be possible to design a garment ,or accelerometer triggered device , that will exert external pressure on the calf at the exact point in the gait cycle when reflux past incompetent venous valves is likely to occur ? This applied external pressure may need to be of only very short duration .

    That is just an unexplored idea of course but you can see how realizing the importance of the the centrifugal effect on venous return changes ones focus .
    Last edited by Gerrard Farrell; February 14, 2019, 02:21 PM.

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  • Gerrard Farrell
    replied
    Re: Centripedal forces and the calf muscle pump

    Hi Adam ,

    The site moderator suggested that a physiologist might be able to help progress the thread further , so I was happy to see that some else had responded who might indeed be a physiologist or have the relevant expertise to assist .

    However , you seem to have dismissed the main thrust of the thread to pursue material which , for this thread , is largely off topic .

    Could we bring things back to foot pumps, calf pumps and when required to explain things , bottles of sauce .

    I would be delighted to hear what you think about the centrifugal effect and venous return . I believe the subject is important but seems to be largely unexplored .

    Gerry

    PS Is the study of the mechanics of the cardiovascular system not biomechanics ?
    Last edited by Gerrard Farrell; February 12, 2019, 05:00 AM.

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  • Adam Clansey
    replied
    Re: Centripedal forces and the calf muscle pump

    Hi Ton,

    Can I digress back to biomechanics from the bottle of HP sauce (neat analogy though Gerrard). ;-)

    You mentioned sprinting in one of your previous posts, but I was wondering whether you came across any observations from a biomechanical perspective that distinguishes sprinting from running? Based on the seminal work of Cavagna and Alexander they showed that running can be dissociated from walking by differences in potential and kinetic energetics, sudden change in froude number (critical point at 0.5) and aerial phase versus no aerial phase. However, despite these claims I did noticed that Martyn Shorten, Ned Frederick and Dirk De Clercq recently presented and published an article on another form of human locomotion pattern called ‘grounded running.’ These guys characterized this locomotion pattern (observed in recreational runners) by having no aerial phase but the potential and kinetic energy dynamics are in phase i.e. similar to running. I suspect however that this mode of transport is heavily weighted on an individual’s body mass, speed, fatigue level and efficiency.

    From my understanding sprinting can be dissociated from running by a physiological perspective/dimension (e.g. anaerobic metabolism), a psychological perspective (e.g. perceived effort or intensity), and possibly a motor control perspective (e.g. max/large neural drive) but are there any biomechanical aspects of ‘sprinting’ that can dissociate it from running? Or is it just running and if so, are we okay to characterize sprinting from another perspective?


    Adam

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  • Gerrard Farrell
    replied
    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 9, 2019, 08:12 AM.

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  • Ton van den Bogert
    replied
    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

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  • Gerrard Farrell
    replied
    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 8, 2019, 07:56 AM.

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  • Ton van den Bogert
    replied
    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.

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