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'Core stability' of the foot

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Mar 22, 2014.

  1. NewsBot

    NewsBot The Admin that posts the news.


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    The foot core system: a new paradigm for understanding intrinsic foot muscle function
    Patrick O McKeon, Jay Hertel, Dennis Bramble, Irene Davis
    Br J Sports Med doi:10.1136/bjsports-2013-092690
  2. This one be an interesting one to read. If anyone has access to it, I would appreciate a copy. kevinakirby@comcast.net

    Foot core? Why can't they just call them intrinsic muscles like everyone else already else does?
  3. Craig Payne

    Craig Payne Moderator

  4. Admin2

    Admin2 Administrator Staff Member

  5. davidh

    davidh Podiatry Arena Veteran

  6. I made this comment on Craig's Running Research Blog about the paper.

    "I just read the paper and can’t say that I was very impressed with any of it as being “a new paradigm” for understanding the function of the intrinsic muscles of the foot. The only thing that is “new” about this paper is that they came up with a catchy new name “the Foot Core System” to describe the function of the smallest muscles of the lower extremity: the intrinsic muscles of the foot. To sayl this paper describes “a new paradigm” is quite a stretch, at best.

    The one positive aspect of this paper is that it did emphasize the intrinsic muscles of the foot which are often ignored and should be considered when biomechanically induced pathologies of the foot and lower extremity are being considered. However, that being said, there are many things that I don’t like about this paper.

    Contrary to what the authors imply in their paper, many authors have discussed the function of the intrinsic muscles of the foot over the past century and, from what I have read of their descriptions over the past three decades of my podiatric medical career, they seem nearly identical to the descriptions that McKeon et al give as descriptions of the function of these small muscles in this new paper. The plantar intrinsic muscles serve to help support the longitudinal arches of the foot and flex the digits at the metatarsophalangeal joints, something that has been said in the medical literature repeatedly over the years.

    However, something that has also been said by these other authors before McKeon et al proposed their “new paradigm” is that the intrinsic muscles of the foot are so small that they really should be considered as muscles that “assist” the functions of the larger extrinsic muscles of the foot (i.e. gastrocnemius, soleus, posterior tibial, flexor hallucis longus, flexor digitorum longus, peroneus brevis, peroneus longus, extensor halluxis longus, extensor digitorum brevis and peroneus tertius muscles) and have no real unique functions that the extrinsic muscles don’t already have. Collectively calling these muscles the “core of the foot” is like calling the palmar intrinsic muscles of the hand the “core of the hand”, or the facial muscles “the core of the face”. In other words, calling these small muscles “core muscles” sounds ridiculous to me and, in my opinion, does not in any way help us understand the function of the foot and lower extremity.

    Finally, the suggestion in the paper that foot orthoses need to only be worn for a short period of time before they should be removed does not, at all, coincide with my 30 years of treating foot and lower extremity injuries with premade and custom foot orthoses. The authors state “Current clinical guidelines include the use of foot orthotic devices for heel pain and plantar fasciitis, but lack any reference to strengthening of the foot. While temporary support may be needed during the acute phase of an injury, it should be replaced as soon as possible with a strengthening programme just as would be carried out for any other part of the body.”

    This statement makes it sound as if foot orthoses actually weaken feet which the scientific evidence does not show. Do the authors actually think that these little muscles of the foot can actually prevent the arches of the foot from collapsing by themselves without a foot orthosis in patients with significant flatfoot deformity? I certainly hope not. And to say that there is no reference to strengthening of the plantar intrinsic muscles in the literature for treatment of plantar fasciitis is simply wrong. Here are a just a few papers published years before McKeon’s paper where the concept of strengthening intrinsic foot muscles for plantar fasciitis is discussed.


    MW Cornwall, TG McPoil Plantar fasciitis: etiology and treatment, – Journal of Orthopaedic & Sports Physica, 1999.

    T. J. Chandler, W. B. Kibler A Biomechanical Approach to the Prevention, Treatment and Rehabilitation of Plantar Fasciitis. Sports Medicine, May 1993, Volume 15, Issue 5, pp 344-352.

    Roxas, Mario:plantar Fasciitis: Diagnosis and Therapeutic Considerations.Alternative Medicine Review . Jun2005, Vol. 10 Issue 2, p83-93.

    Do optometrists, opthamalogists and other medical eye specialists tell their patients to only wear their prescription eye glasses a short period of time until their symptoms of headaches disappear when trying to read so that they can then “strengthen the core muscles of their eyes” to be able to read better? No. In much the same way, some people can quit wearing their orthoses for period of time and not have a return of symptoms. However, to think that all foot orthoses should be discontinued in patients because of some odd belief that foot orthoses “weaken feet” is based only on the unsupported conjectures of the barefoot and minimalist running shoe zealots, is not based on scientific research and is not consistent with the clinical observations of myself , and many other sports podiatrists, over the past half century regarding the foot strength of their patient who habitually wear foot orthoses.

    Is the “Foot Core System” a “a new paradigm for understanding intrinsic foot muscle function”. No. Is the “Foot Core System” a new name for something that has previously been published, sort of like making up the name “minimalist running shoes” to describe the racing flats that had existed for four decades before the “minimalist running shoes” was made up? Yes.

    If anyone wants to read some good research on the plantar intrinsic muscles, Luke Kelly’s research is fantastic and is really ground breaking stuff….and Luke doesn’t call them “core muscles of the foot” either!

    Kelly LA, Kuitunen S, Racinais S, et al. Recruitment of the plantar intrinsic foot muscles
    with increasing postural demand. Clin Biomech (Bristol, Avon) 2012;27:46–51.

    Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch
    LA Kelly, AG Cresswell, S Racinais, R Whiteley, G Lichtwark
    Journal of The Royal Society Interface 11 (93), 20131188

    Dynamic function of the plantar intrinsic foot muscles during walking and running
    L Kelly, G Lichtwark, A Cresswell
    Journal of Science and Medicine in Sport 16, e4-e4

    Discharge properties of abductor hallucis before, during, and after an isometric fatigue task
    LA Kelly, S Racinais, AG Cresswell
    Journal of neurophysiology 110 (4), 891-898

    Do Foot Orthoses Alter Muscle Activation, Running Economy and Neuromuscular Fatigue During a 1-h Treadmill Run?: 843: June 1 2: 15 PM-2: 30 PM
    LA Kelly, O Girard, S Racinais
    Medicine & Science in Sports & Exercise 43 (5), 101."
  7. Craig Payne

    Craig Payne Moderator

    As I see it, the basis of the problem with the concept of core stability advanced in the paper is the timing of the firing of muscles.

    For spinal core stability, the small muscles with poor lever arms do the stabilizing so the larger muscles with bigger lever arms do the movements after the small muscles have done the stabilizing.

    They tried to apply that to the foot: the small intrinsic muscles with poor lever arms do the stabilizing of the arch, so the larger external muscles do the movement.

    The problem is that during dynamic gait, the larger external muscles fire before the small intrinsic muscles ... so the stabilization is not going to happen.
  8. Dennis Kiper

    Dennis Kiper Active Member

    As I see it, core stability starts with the structure. I totally disagree with the statement “stability of the arch is controlled by intrinsic and extrinsic muscles” . The greater the congruency of the joint articulations, the greater the lever arm efficiency for the muscles to work around.
  9. BEN-HUR

    BEN-HUR Well-Known Member

    Just some thoughts (albeit, I'm unable to read the full paper - just abstract with Craig's & Kevin's review on the RRJ blog).

    Muscles are important - all have a role to play... however, not wanting to be discriminatory - some muscles are more important than others (particularly in dynamic function). Even muscles attracting the antiquated opinion of being vestigial i.e. the Plantaris - of which is now classified as a "parallel muscle combination (PMC)" - a sensory/proprioceptive muscle (i.e. has a lot more muscle spindles than Gastroc) to the Triceps Surae group - thus has purpose/function... but it would seem not as important as other muscles (as some individuals function without it or function fine after it has been excised).

    I personally have no problem with the term "core muscles"/"core stability"... pertaining to the trunk that is. The core muscles (providing stability thereof) of the trunk are important; I know this from my training as a runner... this awareness has certainly been amplified since taking up surfing where the core muscles are important for balance (i.e. prevent unwanted movement) as well as re-distributing force (i.e. stabilize & transfer force so as excess force is not targeted to one spinal segment e.g. lumbar) & re-directing force (i.e. creating a change in movement via your core muscles acting as the point where the force transfers through the body e.g. rotating to change direction)... read more here: The Two R’s of Core Training.

    "The foot core system": Hmmm... I think the terminology is overemphasizing the nature of the muscles (group i.e. intrinsics) involved. Like I said, all muscles are important (i.e. synergetic qualities), however some (i.e. Transversus Abdominis, Erector Spinae) are worthy of attracting certain (i.e. "core muscles"/"core stability") terminologies (semantics aside between professionals), whilst I feel other muscles should not attract such classification due to their holistic role in physiology/biomechanics. If some "experts" have issues with the larger trunk muscles attracting such terminology, then the "foot core system" (& those who coined it) should expect some bewilderment & subsequent critique regarding terms such as "foot core stability"... in the context of the paper (& 'posturology')... pertaining to much smaller foot muscles... subjected to the vast/variable array of body masses (large percentage of which are classified "overweight") which are located vertically above them, along with the Earth's gravity... & subsequent forces associated with walking... more so running. [I.e. accumulative force directed to the feet with my relatively light body frame of 67kg (6'2" height) over a 10km run alone will attract around 700 - 800 tonnes of force] Then there are the (biomechanical) structural issues pertaining to the likes of a medial deviated STJ axis (to varying degrees, of which I would think is present in a relatively high percentage of the population [in part the result of Genetic Entropy]) - do these "core foot" (intrinsic) muscles have sufficient leverage & size to stabilize the midfoot (longitudinal arch) against the magnitude of body weight/forces? With this in mind, would they help support relevant extrinsic muscles ("global movers" i.e. Tib. Post.) in supplying an adequate (internal) supinatory moment (force)... despite the suggested added focus on specific training for these intrinsic muscles for increased strength? This condition (i.e. pronounced medial deviated STJ) will not go away, thus is it any wonder that patients benefit from long term use of orthoses, providing there is adequate resistance/stability (supinatory moment) to reduce forces & subsequent injury (i.e. boost injury threshold) &/or conditions (i.e. prevent Tib. Post. Dysfunction).

    Also, Craig's point on the firing of these small intrinsic muscles is important to consider i.e. "do not actually start working until the later half of the stance phase after the extrinsic muscles (global movers) have already started working or firing". Furthermore, as far as the... "intrinsic muscles not active unless there is a perturbation" - maybe that's why speed & gait stability (dynamic balance) seemed to improve with the wearing of custom foot orthoses (i.e. noted in this study... A proof-of-concept study for measuring gait speed, steadiness, and dynamic balance under various footwear conditions outside of the gait laboratory).

    I'm all for conditioning the body - strengthening muscles, but what stipulates an adequate conditioned group of intrinsic muscles for an individual - what level of strength is required to adequately achieve the paper’s/researcher’s intentions... particularly when the issue of intrinsic muscle strength assessment appears to possess many challenges (i.e. an objective measure of intrinsic muscle strength is needed - & without inciting the extrinsics)... highlighted in this paper: Importance and challenges of measuring intrinsic foot muscle strength. For want of better analogies, could this be akin to fitting a Porsche engine in an old VW, or working on strengthening the Plantaris muscle (if it could be isolated) to aid in stronger plantar flexion (i.e. defeating the purpose for its intended design/function). I haven’t had time to look into this (hence, putting it out there), maybe the prime role of the (foot) intrinsics are similar to that of the Plantaris – in that they are more sensory/ proprioceptive muscles as opposed to motor muscles (have more sensory function to that of motor function).

    I have been reading a lot of research papers of late (increasingly over the past 10 years)... some of which embedded with a history of controversy (particularly those challenging world views & even challenging today's empirical data/science) & have thus certainly exercised my "critical eye" (reminded by Dr Kirby) where one can start to pick up on the conscious/subconscious agendas & subsequent biasness i.e. "cherry picking" (picking data which fits one's world view) or exercising The Procrustean Approach (pertaining to Greek mythology - Procrustes - forced to fit a set view/paradigm i.e. it is either stretched to fit, or cut off/discarded if it doesn't) & any number of fallacies (i.e. confirmation bias, proof by assertion, Ipse dixit, affirming the consequent, guilt by association). With this in mind, could one be excused for questioning why the word "core" (with its hierarchical connotations) has found its way into this topic... & the possible agenda that entails... particularly when one is aware of the past history of at least a couple of the contributing researchers i.e. Dennis Bramble (association with Lieberman & 'How running made us human' & 'A softer ride for barefoot runners' papers - with their evolutionary inspired nonsense [albeit the physiology aspect was interesting]) & Irene Davis (i.e. Running Barefoot website & Foot strike patterns and collision forces in habitually barefoot versus shod runners paper). I'm not questioning their integrity, just the nature of their position on the topic & the research (i.e. as per The Importance Of Researching The Research & Good Scientist! You Get a Badge).

    Now I am not an "anti-barefoot" proponent (it has some merits - particularly as a training tool), I do it myself from time to time (even been called a "Barefoot Podiatrist" by the owner of a leading Sydney running store - which I didn't encourage) & have been training in what is now deemed "minimalist" shoes well before the trend took hold (since the late '80's), even have two pairs of those 5 finger shoes... but I do endeavour to be objective in such discussions & realise that truth mixed with error will lead to deception (usually inspired by an agenda) & inevitably lead to false/incomplete conclusions (& potentially the above cited traits i.e. biasness, The Procrustean Approach).

    When all is said; thinking of matters of this nature, I'm reminded of the inspiring American miler - Glenn Cunningham... who overcame tragedy & physical trauma to become what many consider as the greatest American miler of all time, an Olympic silver medallist (1936), multiple world record holder (800 - 1500m) & world # 1 (story here - Forgotten Stories of Courage and Inspiration: Glenn Cunningham).

    The term "transverse arch" was mentioned in many articles I read... putting aside what they actually meant by this term, I think by the description of his injuries we could conclude that the intrinsics were likely badly affected (i.e. "Glenn had lost all the toes on his left foot, and the transverse arch of the foot was ravaged")... one could be excused to question the motor function importance of the foot intrinsics within this successful athlete... in a demanding sport such as middle distance running... & hence the real world practical significance of the paper's "foot core stability" position.
  10. Craig Payne

    Craig Payne Moderator

    ...yes, the paper did talk about the anterior metatarsal arch; I did not bother mentioned that in my review. Shame they missed the evidence that it does not exist.
  11. MaireMurph

    MaireMurph Member

    I find referring to the intrinsic muscles of the foot as the "core muscles" helps patients to understand their importance so I don't think this wording should be dismissed.
  12. Why instead of using a word that doesn't really mean anything like "core muscles", just telling your patient that these muscles are important for their foot health? How does changing the name of muscles of the foot help change their importance?

    If you really think that changing the name of a group of muscles of the body that have had the same names for the last century will change their importance to patients then just call them "important muscles" instead of "core muscles". In that way, you wouldn't then have to explain to them what "core" actually means.

    As a matter of fact, Maire, please define what the term "core muscles" actually means since I don't have a clue!
  13. MaireMurph

    MaireMurph Member

    You or I might not have a clue but the patients do and we need to be able to communicate with them.
    It's all very well to maintain a pureist philosophy but at the end of the day we are practitioners dealing with people who think in a different way to us and they are the priority. That's actually why we exist.
  14. That's why you should say these small muscles of the foot are "important" and are not a "core", because most people know what "important" means and I have yet to hear anyone tell what a "foot core" is. Why make up a word that only confuses things? I exist to help people, not confuse people.
  15. HansMassage

    HansMassage Active Member

    " We draw the parallels between the small muscles of the trunk region that make up the lumbopelvic core and the intrinsic foot muscles, introducing the concept of the foot core."

    I agree with Kirby; Trying to improve communication by using a popular term that is miss applied by the majority is not going to help our clients in the long run.

    Most advocates of "core training" train the extrinsic muscle of the trunk and ignore the intrinsic. Therefore the application of "core" is contrary to general public understanding.

    The experienced authors on the forum have pointed out that the intrinsic muscle fire to correct protuberances of movement. This is what I find with the spine. The "knots" in the paraspinals can be traced to supporting aberrant movement in the extremities. Maybe a ridged big toe.
  16. Craig Payne

    Craig Payne Moderator

    Here are a couple of more spins on this article:

    Christian Barton:

    Casey Kerrigan:

    ...one of them is gushing and shows a complete lack of understanding and critical thinking skills; the other is not bad.

    My issues with all this are still:
    1) The intrinsic muscles do not fire until later in the stance phase during gait (check any muscles firing timing chart), so does not matter what you do to exercise them, its going to have no effect until then (assuming that it can have an affect)...and the vast majority of people who prescribe these exercises do so for problems that occur prior to midstance! ... go figure!
    2) The muscles are tiny (so how strong can they get with rehab?) and if they do support the "arch", they have to do so by plantarflexing the mets; yet they run almost parallel to the mets and have a minuscule lever arm in which to do this --> not very effective, if effective at all.
    3) None of those that keep harping on about this have ever been able to explain the clinical observation that a weakness of these muscles can lead to a higher arched foot, for eg, the 'intrinsic minus foot' in diabetes.

    I have no problem with rehab/exercises aimed at this and do it clinically; I just don't have any great expectations that its the 'holy grail' that the article promotes it to be. What is the point in doing any exercises just for the sake of doing exercises?
  17. The only people who get excited about this article are those who believed Mark Cucazella's bizarre comment that the only effective treatment for plantar fasciitis is strengthening of the foot. When will the barefooters just realize that they are fighting a losing battle in their quest to promote barefoot running and minimalist shoes?

    Sorry, must go now.....it's time to do my toe strengthening exercises since I wore shoes and orthotics all day....:bang::bash::boxing:
  18. CraigT

    CraigT Well-Known Member

    From the Casey Kerrigan reference above...

    Personally I have generally found that so called 'arch support' in shoes does bugger all.
    Fortunate for her that the only shoe on the market that doesn't do this is the one that she has developed and marketed.

    Any idea the study she is referring to here?
  19. Craig Payne

    Craig Payne Moderator

    Like a lot of the stuff she writes, she is making it up and the fan boys fall for it.. No study has shown that! In fact, the opposite has been shown by this study:

    I spoke with a lot of retailers at the PAC conference last week - they now can't give vibrams etc away!
  20. NewsBot

    NewsBot The Admin that posts the news.

    Freeing the Foot
    Integrating the Foot Core System into Rehabilitation for Lower Extremity Injuries

    Patrick O. McKeon, PhD, ATC, CSCS, François Fourchet, PT, PhD
    Clinics in Sports Medicine; Article in Press
  21. NewsBot

    NewsBot The Admin that posts the news.

    Foot core strengthening: relevance in injury
    prevention and rehabilitation for runners

    Fourchet F, Gojanovic B
    Swiss Sports & Exercise Medicine, 64 (1), 26–30, 2016 (full text)
  22. NewsBot

    NewsBot The Admin that posts the news.

    Protocol for evaluating the effects of a therapeutic foot exercise program on injury incidence, foot functionality and biomechanics in long-distance runners: a randomized controlled trial
    Alessandra B. Matias, Ulisses T. Taddei, Marcos Duarte and Isabel C. N. Sacco
    BMC Musculoskeletal Disorders 14 April 2016

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