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Foot Orthotics and Weakening of Muscle Strength?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Oct 10, 2017.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

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    The Effects of a 12-Week Custom Foot Orthotic Intervention on the Intrinsic Muscles of the Foot, and Dynamic Stability During Unexpected Gait Termination in Healthy Young Adults
    Protopapas, Katrina,
    Theses and Dissertations (Comprehensive). 2017
     
  2. Admin2

    Admin2 Administrator Staff Member

  3. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Interesting to see how this plays out ...
    I only have access to abstract and not full methods to appraise, but it looks OK from the abstract. Lets see if it gets published in full.

    So what we have:
    1 cross sectional case control study showing a weakness (published)
    1 cross sectional study showing orthotic group stronger (unpublished but in public domain))
    1 prospective study showing a decrease in strength (unpublished thesis abstract)
    2 prospective studies showing an increase in strength (published)
    1 prospective study showing no change in strength (unpublished but in public domain)
     
  4. efuller

    efuller MVP

    " With the plantar intrinsic muscles of the foot being in direct contact with the CFO, it puts these structures at risk for disuse muscle atrophy as a result of being offloaded."

    I'm still trying to figure out how the orthotic being in contact offloads the intrinsic muscle. That statement doesn't really matter if the research question is do orthotics change the strength of intrinsic muscles. They would still have to look for both increase in strength and decrease in strength. ​
     
  5. A change in cross sectional area of a muscle does not mean it is weaker. It means it has a decreased cross-sectional area. Period. We don't know how much cross-sectional area each plantar intrinsic muscle needs to be considered "weak". In other words, how much loss of cross-sectional area makes a plantar intrinsic functionally "too weak". Will the CNS will simply recruit more of the muscle when demands are high in a plantar intrinsic muscle, making it slightly smaller but more efficient? We simply don't know.

    My guess is that the orthosis is reducing the demand on the plantar intrinsics over time thereby reducing it's cross sectional area. It remains to be seen 1) does a small decrease in plantar intrinsic muscle cross-sectional area result in any functional differences in foot function (I tend to doubt it), and 2) what is the minimum muscle strength needed in the plantar intrinsics in order for the CNS to allow the foot function normally (we don't know that either).

    I predict that there will be a number of physiotherapists and barefoot/minimalist shoe advocates who will latch onto this study to declare that foot orthoses should only be used short term since they cause "foot weakness" over time. I'm sorry, after treating ten's of thousands of people with foot orthoses over the last 30+ years, I have yet to see one single patient develop "foot weakness" from wearing their orthoses on a regular basis. I tell all my patients to keep their orthoses inside their shoes if they are making them more comfortable, but take them out if they are causing discomfort. There are no negative health consequences to wearing well-made custom foot orthoses for years upon years. If someone tells you that, ask them to produce the evidence otherwise. There is none.
     
  6. markjohconley

    markjohconley Well-Known Member

    "With the plantar intrinsic muscles of the foot being in direct contact with the CFO, it puts these structures at risk for disuse muscle atrophy as a result of being offloaded."
    How does this work? No muscle is in 'direct contact' with the foot orthoses. If 'in contact' how would that necessarily 'offload'?
     
  7. Mark,

    This is pure conjecture and makes me worry about whether the researchers doing this study had a pre-research agenda to push across that foot orthoses "weaken" feet. It really is nonsensical since the skin is first in contact with the orthosis, then the subcutaneous fat, then the plantar aponeurosis and finally the plantar intrinsic muscles. Why don't the skin, adipose and plantar fascia atrophy also when wearing foot orthoses? Ridiculous!
     
  8. don't we also have Lukes study saying the intrinsic muscles are more Active when there is an orthotic being warn ?
     
  9. Not really on subject but this is not quite true, We have discussed anti pronation devices may increase the likelyhood of Medial knee OA, and everytime an orthotic is warn, certain sections of the body will be getting an increase in stress, while others less, so while it may be impossible to say over years and years ( decades even) devices may lead to breakdown in soft tissues, it is just impossible to say that there are no negative Health consequences. yes it is hair splitting
     
  10. markjohconley

    markjohconley Well-Known Member

    Apologies Eric, I missed your post till now. Obviously I would not have posted later in the thread if I had so, all the best, Mark
     
  11. toomoon

    toomoon Well-Known Member

    I completely agree.. consider elite downhill skiers who are encased in very rigid footwear or elite cyclists who spend hours in rigid footwear. Is their cross-sectional area compromised directly relating to strength.. I doubt it. It may well be that this is simply a normalisation back to a more functional cross-sectional area. but, as you say.. we simply don't know. Too early to jump to big conclusions though. I look forward to the deafening noise of practitioners bleating that orthoses cause weakness!
     
    Last edited by a moderator: Oct 16, 2017
  12. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I shared this widely on social media a week ago .... deafening silence from those fan boys so far...
     
  13. Dieter Fellner

    Dieter Fellner Well-Known Member

    Haven't read the full paper, but really? Might as well speculate the 'intrinsic' musculature was hypertrophied due to abnormal foot instability and recruitment of intrinsics in an attempt to stabilize the foot, a condition which was then restored with the use of foot orthosis.

    What's next, the world is flat (wait, it might be....)
     
  14. scotfoot

    scotfoot Active Member

    If skeletal muscle is subjected to repeated compression , such as would occur in the abductor hallucis with the use of an orthotic that included a medial arch support , would this lead to a muscle with a reduced intersitial fluid content ,and hence reduced cross sectional area ?

    Also , in the case of older individuals with age related intrinsic muscle atrophy , I wonder if the exercises of Mickle et al 2016 , might improve orthotic efficacy by restoring intrinsic volume . What say you Dieter ?

    Gerry
     
  15. scotfoot

    scotfoot Active Member

    On a similar theme , would increasing the volume of the intrinsic foot muscles in the intrinsic minus foot help improve the effectiveness of a medial arch support ? I believe it would .
    So can this volume increase be achieved ? We are about to find out . (see PDF link below )
    Could be a very important piece of research .
    Evaluating a foot strengthening exercise program to improve foot ...
    https://249kl22iwv073rrkjr3zufqg-wpengine.netdna-ssl.com/.../Project_Summary_te...18 Apr 2017 - Evaluating a foot strengthening exercise program to improve foot function ... Victoria University: Dr Karen Mickle, Professor Rezaul Begg and ...
     
  16. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    This is of relevance to the findings of the above study:
    Correlations Do Not Show Cause and Effect: Not Even for Changes in Muscle Size and Strength
    Scott J. Dankel et al
    Sports Medicine January 2018, Volume 48, Issue 1, pp 1–6
     
  17. gregori

    gregori Member

    Hello everyone, first post here :s.

    Very interesting study, although I might not understand it as an english-speaking person will, I guess I still got the gist of it.

    I have also been taught in french podiatry schools that orthotics and especially "arch height" will render our tibs lazy and weak. Then, when talking with serious podiatrists in France, they told me that it was something thought without really much consistency. I wish they could be here to explain that themselves but english is not their main language so I will try to do it myself and stay genuine to their utterances. I do not master it as they do so there might be some inconsistencies. Here is what they said :

    If you put something hard under the foot, this compresses sensors in muscles and tendons in contact and they contract as a response. If, my memory is not lazy (must be my orthotics that cause that ;)) I think this was due to Golgi sensors which cause muscle contraction when pressured.
    as opposed, if something soft is placed under the foot, sensors will not be triggered and no muscle response will happen.

    Even though this is not a serious study, I remember that we did the test with the plateforce and the "game" was to observe the different reactions people had when poron and a stiff material of 70 shore+ were put under some parts of the foot. Even though, that did not work 100% of the time, for most of it the soft material would " attract " the foot to its location ("shutting down" sensors = no muscle reactions to counter ground reaction force) and the stiff material would "repulse" the foot.
    Here is a little thing you can do : try putting a heel rise of 2mm of poron on your shorter leg. If you tend to put most of your weight on your longer one, normally what you will see in the plateforce is that your weight will shift onto your shorter leg. Hopefully with the above explanation, I made the relation clear. It did pretty well in dynamic too.

    I am curious of what you guys think of it, as I haven't read much podiatry literature in my life it is hard to criticize another's opinion for me (I am also pretty new to podiatry).

    Gregori.
     
  18. efuller

    efuller MVP

    Welcome Gregori.

    If the orthotic makes it so the person walks more, they will be using their muscles more. In gait, when the heel lifts off of the orthotic, the posterior tibial muscle will lose any help it was getting from the orthotic. So, with walking, the posterior tibial muscle is used even with orthotics.


    The sensors are not directly connected to the muscles. The CNS (central nervous system) will activate muscles in response to discomfort to alter pressure under the foot.

    The reason that it did not work 100% of the time is that the response is filtered through the CNS. Are you familiar with the concept of postural sway. The center of mass is constantly moving over the foot. The foot muscles have to contract to shift the center of pressure under the foot to a location that will push the center of mass back towards the center of the base of support. Putting something under the foot can make the CNS chose a different location to balance around.

    Eric
     
  19. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    You were taught wrong. ALL the actual evidence says the opposite, with the possible excpetion of the one study above.
     
  20. gregori

    gregori Member

    At first glimpse, postural sway didn't ring a bell until I looked it up on the internet and see to what it corresponds. Thank you for the explanation though, that makes it more clear for me. I am not sure of what I advance as I am not one myself, but in France there is a specialty called "posturology" where podiatrists would more or less use these mechanisms with the CNS to make foot orthotics rather than pure biomechanics. Sometimes it works, sometimes not...

    The more I look at this website and the evidence it supplies us with and the more it gets to my nerves to see how much I paid to have been taught wrong :D.
     
  21. Petcu Daniel

    Petcu Daniel Active Member

    It can be downloaded today from University's website: http://scholars.wlu.ca/etd/1992/
    Daniel
     
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