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  1. #1
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    Centripedal forces and the calf muscle pump

    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; 02-09-2019 at 07:23 AM. Reason: spelling

  2. #2
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    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; 02-09-2019 at 07:25 AM.

  3. #3

    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.

  4. #4
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    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; 02-08-2019 at 07:56 AM.

  5. #5

    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

  6. #6
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    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; 02-09-2019 at 08:12 AM.

  7. #7

    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

  8. #8
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    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; 02-12-2019 at 05:00 AM.

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