Centripedal forces and the calf muscle pump

[Gerrard Farrell]

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

[Gerrard Farrell]

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.

[Ton van den Bogert]

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.

[Gerrard Farrell]

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

[Ton van den Bogert]

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

[Gerrard Farrell]

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

[Adam Clansey]

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

[Gerrard Farrell]

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 ?

[Gerrard Farrell]

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 .

[Adam Clansey]

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

[Gerrard Farrell]

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

[Gerrard Farrell]

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 ...

[Gerrard Farrell]

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 .

[Gerrard Farrell]

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 .

[Joakim Holmberg]

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