Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

The intrinsic foot muscles as shock absorbers

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Aug 4, 2018.

  1. scotfoot

    scotfoot Active Member


    Members do not see these Ads. Sign Up.
    Two recent papers ,taken together , make it increasingly likely the intrinsic foot muscles act as shock absorbers during gait , with their importance increasing as forces increase .

    1
    Conclusion ( Kokamura; see below )

    "Results from this study showed that the functions of the PIFMs most likely include shock absorption and facilitation of efficient foot ground force transmission during the stance phase of gait."

    2
    Conclusion ( Kelly ; see bellow )
    "The foot appears to behave as a viscous spring-damper during running. The underlying mechanism for how this occurs, the varied contributions of all the individual structures, and the subsequent mechanical and energetic consequences require further investigation"

    And

    "Additionally the intrinsic and extrinsic foot muscles have the capacity to act as dampers and motors, dissipating and generating mechanical energy."

    Paper 1

    The effect of additional activation of the plantar intrinsic foot muscles ...
    https://www.sciencedirect.com/science/article/pii/S095825921730086X
    by K Okamura - ‎2018 - ‎Related articles

    Paper 2

    The energetic behaviour of the human foot across a range of running ...

    www.nature.com › scientific reports › articles12 Jul 2018 - The plantar intrinsic foot muscles are a group of muscles located within the foot, spanning a similar anatomical pathway to the Plantar Fascia (PF)13,14.
     
  2. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Yep; that is pretty much what Luke's work showed.
     
  3. scotfoot

    scotfoot Active Member

    So if you add in the idea of a primary windlass phase ,were the toe extensors (and in particular the extensor hallux longus -Zelik ) dorsiflex the toes prior to foot strike , then pay out the plantar fascia via eccentric contraction as weight acceptance develops ,then we have the intrinsic and extrinsic foot muscles "acting as dampers" and so protecting the structures of the foot from excessive load transients .

    As we age ( over fifty ) muscle strength declines even with if prior running activity levels are maintained . This is true of the foot intrinsics giving a less effective dampening system in the foot . How do you reverse muscle loss caused by aging ? Mickle has shown that this can be achieved by progressive resistance training .

    I have to say that with a few exceptions (Nester ) all the best research seems to be coming from the Australians . Hands down !
     
  4. efuller

    efuller MVP

    The "dampers" are what is loaded when the shock is absorbed. The dampers are under high load to protect other structures. Some structures will have increased load to decrease load in other structures. The muscles have higher loads to reduce the load on plantar ligaments of the arch, in the case of arch flattening.

    Also, we should look at the relative contribution of all structures that reduce peak forces. The concept of impulse is important here in understanding how downward moment of the body is stopped. Impulse is force x time. A certain amount of impulse is needed to stop downward momentum. A high force for short amount of time, or a lower force for a longer amount of time will produce the same impulse. The force applied is reducing the downward velocity to zero. So, the object is moving as the force is applied so you have to take into account the distance traveled while the force is applied. If you only have a short distance, you can apply low force for a short time before you get a force peak.

    Things that contribute to shock absorption. Knee flexion, in heel strikers, ankle plantar flexion, and arch flattening. Arch flattening looks like the smallest percentage of distance traveled of those three. Yes, it does contribute, but not as much as other things.

    So, Gerry, when are you coming out with the arch strengthening machine? Is there some other reason for your interest in the intrinsics?
     
  5. scotfoot

    scotfoot Active Member

    Eric said -

    "Things that contribute to shock absorption. Knee flexion, in heel strikers, ankle plantar flexion, and arch flattening. Arch flattening looks like the smallest percentage of distance traveled of those three. Yes, it does contribute, but not as much as other things. "

    One of the most important findings of Luke Kelly's paper "Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch " ( see link below and especially fig 1 ) was that loading of the foot alone produced an increase in the activity of the plantar intrinsics ,with activity increasing with load .

    It would seem that as well as being part of an overall foot /leg /spine shock absorbing system the foot has its own closed loop system , that in my opinion , is probably controlled by strain within the plantar fascia . It is therefore not correct to view the flattening of the arch as merely a smaller part of a larger whole since the foot seems to be able to regulated stresses within the foot tissues independently of the stresses within the rest of the leg . This is an extremely important finding and is one of the features which makes Kelly's work so valuable and illuminating .

    Eric said
    "Is there some other reason for your interest in the intrinsics?"

    A more interesting question would be -why Root's lack of interest ?




    Intrinsic foot muscles have the capacity to control deformation of the ...

    rsif.royalsocietypublishing.org/content/11/93/20131188
    1. Similar
    by LA Kelly - ‎2014 - ‎Cited by 65 - ‎Related articles
    29 Jan 2014 - Luke A. Kelly, Andrew G. Cresswell, Sebastien Racinais, Rodney .... All participants were informed of the study requirements, benefits ...... 2012 Recruitment of the plantar intrinsic foot muscles with increasing postural demand.
     
    Last edited: Aug 6, 2018
  6. efuller

    efuller MVP

    Kelly's work talks about the intrinsics affecting arch deformation. You cannot consider arch deformation without looking at the forces that cause arch deformation. Body weight and body momentum is what causes arch deformation. I disagree with your contention that it is not correct to view the flattening of the arch as merely a smaller part of a larger whole. The foot may independently regulate its stiffness. However, that is a different issue than load on the foot. And we are not just talking about arch deformation. We were talking about "shock". Shock is caused by deceleration of the total body. So, you cannot separate out the contribution to shock absorption from the foot from the contribution from other joints.
     
  7. scotfoot

    scotfoot Active Member

    Eric ,
    What I am saying is that the extent to which different tissues within the foot are subjected to shock or rapid loading is controlled not only by the foot /ankle /leg system as a whole , but also by a separate system in the foot . If the foot has stresses to deal with it "has options " . To much strain on the fascia and intrinsics can be recruited in the way that Kelly has illustrated or via the " initial windlass mechanism" .
    Also I feel that the initial windlass mechanism is likely to be a more important contributor to whole body shock control than you might think -but the idea is too new to have been tested .

    I do not believe you can have a tissue stress theory for the foot without realising the foot has its own control system and without taking cognisance of the initial windlass phase .
     
  8. efuller

    efuller MVP

    The paper you cited shows that the foot has a mechanism for absorbing shock. I have not been disputing that. What I have been pointing out is that we should look at the relative contribution of each part of the whole mechanism to the problem at hand. If the problem is shock from landing then we need to look at the distance over which that shock can be absorbed. There is more distance for the knee and ankle than there is for the foot. You are welcome to do some calculations to examine the relative contribution of each segment. I'm just saying that we should not focus, excessively, on one part of the whole, that appears to contribute less than other parts.
     

  9. Yep. Add the hip to the knee and the ankle while important the foot will generally play a lesser role
     
  10. scotfoot

    scotfoot Active Member

    The foot ( taken as a whole ) knee and hip can be viewed as being in series and , as previously described by Kevin , the structures within the foot can be viewed as being in parallel . The closed system within the foot is key to tissue stresses within the foot .

    If you add in the new factor of the plantar fascia as a strain gauge , and I believe that is were the evidence now points , you have a situation were afferents from the foot are key to leg stiffness . Fool the fascia and the fool the entire leg into large impact transients .
     
  11. scotfoot

    scotfoot Active Member

    From above -
    "Fool the fascia and you fool the entire leg into large impact transients ."

    Medial arch supports , present in most shoes , are known to reduce the strain in the plantar fascia . Could it be this that convinces the CNS that the underfoot conditions are more compliant than they actually are , resulting in increased leg stiffness and larger impact transients than would otherwise be the case ?
     
  12. scotfoot

    scotfoot Active Member

    So with regard to the impact transients talked of by Lieberman , the barefoot debate should be around medial arch supports and not cushioning ? Easy enough to test .

    Perhaps the footwear industry makes shoes with medial arch supports because they feel more comfortable . The fascia is under reduced load when customers try them on unaware that such shoes could possibly lead to heavy heel striking and associated injuries .

    Please note that I am not talking about properly prescribed orthotics here , just mass produced footwear . Indeed , one of my pet hates is the idea that muscle strengthening can reverse adult acquired flat foot , when the job seems to be done best with a medial support inclusive orthotic .
     
  13. scotfoot

    scotfoot Active Member

    Relevant to this thread , here is a quote from another arena thread -
    The plantar fascia as a strain gauge | Podiatry Arena


    Might one of the major roles of the plantar fascia be that of a strain gauge to keep the CNS up to date with levels of stress being generated in the foot and lower limb during locomotion?

    Consider the following quote from the paper referenced below (1) -

    "There was a statistically significant correlation between the thicknesses of the PF and the paratenon. These findings suggest that the plantar fascia has a role not only in supporting the longitudinal arch of the foot, but also in its proprioception and peripheral motor coordination."

    Yep .Back to proprioception .

    Paper (1)
    Plantar fascia anatomy and its relationship with Achilles tendon and ...

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3842207/
    by C Stecco - ‎2013 - ‎Cited by 70 - ‎Related articles
    12 Sep 2013 - Analyzing its possible connections to the sural structures showed that this fascia is more closely connected to the paratenon of Achilles tendon
     
  14. scotfoot

    scotfoot Active Member

    Some quotes from the paper referenced above on plantar fascia anatomy -

    "The PF was found well innervated, especially where it joins with the fasciae of the abductor hallucis and abductor digiti minimi muscles, and where the sole muscles are inserted. The presence of Pacini and Ruffini corpuscles – usually considered responsible for mechanoreception (Moraes et al. 2008) – suggests that plantar fascia innervations have a role in proprioception and in the stability and control of foot movements."

    And
    " . Thanks to the many muscle insertions, the plantar fascia is capable of perceiving both the foot's position and the state of contraction of the various intrinsic muscles of the foot. If these muscles contract excessively, the PF (and the nerve endings it contains) might be overstretched. These properties of the plantar fascia shed new light on this complex tissue. The fascia could be seen as a coachman guiding the muscles in the sole of the foot and helping to coordinate all these structures during movement "

    In my opinion Kelly's work on loading of the fascia confirms and underlines the proprioceptive and muscle coordinating roles of the plantar fascia .

    If the fascia acts as a control for the intrinsics then it is no great stretch to speculate that it is a vital component in the coordination of the musculature of the rest of the lower limb .

    So perhaps -
    Inappropriate medial arch supports = CNS confusion , leading to injury .
     
Loading...

Share This Page