Some time ago I placed a few posts on a site run by a shoe company . The posts have since been deleted and I still have no answers to the questions raised . Please note that I am not claiming to be an expert in foot anatomy or physiology but I do have a keen interest in the area.



Abstract from site related to an article on the" foot core system" and containing material posted by me -

6 Responses

2.Gerrysays:


November 8, 2014 at 8:03 am


Hi Casey
I enjoyed reading your article but wonder if perhaps the intrinsic muscles of the foot play an important role in supporting the bony arch of the foot even in early stance when they are in a passive state . That is might forces be trasmitted between the bony arch and an under tension plantar fascia via the passive intrinsic musculature . This mechanism could help reduce harmful shearing forces between between the bones of the foot during locomotion and explain the forces which lead to the compression and empting of the vessels of the plantar venous plexus in early stance .
I would greatly welcome any comments on the above .
Gerry Farrell
Glasgow


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Caseysays:

November 10, 2014 at 11:07 am



***Here Dr Kerrigan gave a reply which for copyright reasons I have deleted . In my opinion the reply was not really relevant to what I was trying to say . **

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Gerrysays:


November 11, 2014 at 2:55 pm


Hi Casey
Might it be ,during early stance when the bony arch of the foot lengthens and the plantar fascia becomes tensioned ,that the passive intrinsic musculature located between the arch and the fascia becomes compressed between the two structures (transverse passive compression ) providing support to the arch and a reduction in the shearing forces between the articulating bones of the foot in the midfoot area ?
Also ,might it be that the intermuscular pressure generated through the transverse passive compression of the foot intrinsics ,in the way outlined above , provides the primary force for the compression and empting of the vessels of the plantar venous arch ?
I understand and largely agree with the “foot core system ” outlined in your article ( although I have to say I am not an expert in either foot anatomy or physiology) but believe that the intrinsic muscles of the foot also act as the core of the foot in a much more literal sense .

Kind Regards
Gerry


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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

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The following are extracts from a conversation I had some time ago with a Professor Jason Cholewa .Again for copyright reasons I have reduced Jasons reply on 27 May 2014 to a single sentence .Posts are in reverse chronological order and a link to Jasons site is included .








With regard to my ideas about the possible role that the intrinsic muscles of the foot might play in transmitting forces between the tarsal/metatarsal arch and the planter fascia and to the short foot exercise that you mentioned I had a look for some evidence that this exercise can not only increase the strength of the foot muscles but also that it can increase muscle cross sectional area . I did find one paper (1) that shows that in subjects with pes planus (flat feet ) the short foot exercise can be used in conjunction with foot orthoses to increase the cross sectional area of the abductor hallucis muscle . The abductor hallucis is thought to play an import role in the support of the medial longitudinal arch and I wonder if it may act not only by applying force through its point of insertion but also by acting in concert with the tarsal/metatarsal arch and the plantar fascia to maintain or change tension in the fascia itself.
Kind regards
Gerry (blue)
Gerrard Farrell
Glasgow
Ref (1) Jung Dy ,Koh EK ,Kwon OY Effect of foot orthoses and short-foot exercise on the cross sectional area of the abductor hallucis muscle in subjects with pes planus ;a randomized controlled trial J Back Musculoskeletal Rehabil 2011




By: blue


27 May 2014, 18:40:59 | blue
Hi Jason
Thanks for getting back to me and its good to hear that you think my ideas might have some validity. With regard to the barefoot vs shod running debate I’m afraid I know little about the subject and have more of an interest in agility orientated sports such as tennis and also in the heavy throws .
You mentioned the short foot exercise and it certainly seems to be attracting considerable interest at the moment with new papers being published on a fairly regular basis .
As you have said previously there is still a lot to learn about the human foot !
Kind regards
blue





By: jasoncholewa


24 May 2014, 13:40:53 | jasoncholewa
Blue, I think you are on to something. (Rest of reply deleted for copyright reasons )
Jason





By: blue23 May 2014, 16:55:42|blue


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)




Optimal Sprinting Performance:

jasoncholewa.com/2012/11/.../optimal-sprinting-performance-a-foot-feti...


2 Nov 2012 - What is the missing link in training for athletic performance? ... In theoptimal case your ankle remains fairly rigid and you sprint back up with ...




So why this thread ? With the above in mind does anyone think that a medial arch support might improve venous return from the plantar venous plexus in cases were the intrinsic muscles have been replace by fatty infiltrate?


Gerry


Gerrard Farrell
Glasgow