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New Research on Walking Biomechanics and Rearfoot Wedging

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kevin Kirby, Sep 20, 2009.


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    Newsbot: Walking Biomechanics....not Running Biomechanics!

    http://www.box.net/shared/z9vvdj6lt8
     
  2. Regardless of running versus walking, there does appear to be some trends emerging from foot orthoses research: that kinematic effects are inconsistent and that:
    Interesting. How is the rearfoot inversion (or for that matter) eversion moment calculated in such studies? Is the instantaneous centre of rotation of the rearfoot complex calculated from 3-dimensional kinematic data? Presumable the net ground reaction force vector is then obtained from a 3-dimensional force plate and multiplied by the lever arm to the position of the instantaneous centre of rotation at specific time intervals during the gait cycle- right?

    Why is this finding consistent while other kinetic and kinematic variables show inconsistent changes in association with foot orthoses?
     
  3. Simon:

    The studies that use inverse dynamics calculations can, of course, determine the kinetics of the rearfoot. Unfortunately, they are also all assuming that the foot rotates about an axis that is parallel to the longitudinal axis of the foot, parallel to the sagittal and transverse planes, which is obviously not the case due to oblique nature of the subtalar joint axis relative to all three cardinal body planes. At least we do know that the internal inversion moments are consistently decreasing with foot orthoses which certainly makes sense to me. There are so many possible reasons why other measurement parameters in foot orthosis research are not as consistent as is decreasing internal inversion moments, that it would be hard to speculate. My guess is that decreasing internal inversion moment with foot orthoses is the dominant influence in foot orthoses studies currently just because our foot orthosis researach is still relatively primitive compared to where it will be in 20 years. At least we know that foot orthoses are mechanically doing something consistent (i.e. decreasing internal inversion moment), which is something we couldn't conclusively say even 20 years ago!
     
  4. This is interesting when we draw comparatives with the EMG research which seems to demonstrate consistent increases in tibialis anterior activity which should increase internal inversion moment in a normal STJ axial position- right?
     
  5. Actually, I just spotted this:
    George S. Murley a,b,*, Karl B. Landorf a,b, Hylton B. Menz b, Adam R. Bird:
    Effect of foot posture, foot orthoses and footwear on lower limb muscle activity
    during walking and running: A systematic review. Gait & Posture, Volume 29, Issue 2, 2009


    "foot orthoses increase activation of tibialis anterior and peroneus
    longus, and may alter low back muscle activity"


    Anna Lucy Hatton1, John Dixon1, Keith Rome2 and Denis Martin1: Effect of foot orthoses on lower limb muscle activation: a critical review. Physical Therapy Reviews 2008 VOL 13 NO 4


    "There is some evidence to suggest that tibialis anterior activity while walking is reduced in the presence of FOs. Both Nurse et al.28 and Romkes et al.39 reported a reduction in tibialis anterior activity during gait trials while wearing textured shoe inserts and therapeutic shoes, respectively."

    There you have it, two systematic reviews on the same topic, published less than a year apart and we have two different conclusions. Helpful?

    To be fair, the Hatton et al. paper does then follow this statement with:
    "Previous findings from Tomaro and Burdett26 concluded that semi-rigid FOs caused an increase in the duration of tibialis activity when walking."

    But then it gets a little confusing:

    "This evidence may complement that of decreases in muscle activity observed by Nurse et al.28 and Romkes et al.,39 suggesting that a lower level of muscle activity may equate to greater fatigue resistance."

    I'm probably missing something here, but how does a study that shows "an increase in the duration of tibialis activity when walking" compliment two studies that "suggest that tibialis anterior activity while walking is reduced"?

    "Only Tomaro and Burdett26 investigated participants who presented with pronated feet and a history of lower limb injury. However the similarities [??????? hey?] with the findings of Nurse et al.28 and Romkes et al.39 may suggest FOs are capable of decreasing the muscle force needed to resist foot pronation during the first half of the stance phase in individuals with both normal and abnormal foot positioning.41"

    Sounds like Hatton et al. are bending the evidence to fit with their own point of view. Like I said, I might be missing something....

    The mystery deepens- cud
    "She spends her time just sleeping,
    While the mystery deepens,
    With each wave of her wand."


    As there are four authors to each of these systematic reviews can I suggest a tag match, full contact cage fight to see who is right? Or, should I just read the literature for myself and make my own mind up?

    Oh and BTW, the paper by Murley et al. included all three of the references cited above within the Hatton et al. paper???????
     
  6. markjohconley

    markjohconley Well-Known Member

    How do "varus wedges significantly reduced net ankle inversion moments". I thought it would be the opposite?
     
  7. GS Murley

    GS Murley A Welcome New Poster

    Hi Simon,

    To avoid the full-contact-cage-fight (because Hylton, Karl and Adam would find some wire cutters and do a runner) – I’ll clarify some of the points you raised below.

    We concluded from four studies that some evidence suggests various styles of FOs increase electromyographic (EMG) amplitude of tibialis anterior and peroneus longus (Mundermann et al., 2006; Murley and Bird, 2006; Nawoczenski and Ludewig, 1999; Tomaro and Burdett, 1993). Indeed, there are some issues with comparing these papers and making definitive conclusions. For example, the results of my study (Murley and Bird, 2006) indicated that it was more the effect of the shoe alone that was increasing TA EMG amplitude than the combination of the shoe and FOs. Another example is the Tomaro and Burdett (1993) study, which found TA EMG duration increased with FOs, not specifically the amplitude parameter.

    The other study you mentioned – Romkes J, Rudmann C, Brunner R. Changes in gait and EMG when walking with the Masai Barefoot Technique. Clin Biomech 2006;21:75–81 – did not investigate FOs, rather a ‘rocker’ type shoe. Below is some info taken from this paper about the MBT shoe:

    MBT constructed a shoe with a rounded soft sole in anterior–posterior direction underneath the heel area, providing an unstable base of support with a rocker bottom. The shoes are widely used across Europe but less known around the rest of the world. The theory behind the concept is that the MBT-shoe transforms flat, hard, artificial surfaces into uneven surfaces, simulating the walking action of our barefoot ancestors, thus challenging the muscles to be more active.

    You are right though Simon, there is some conflicting evidence and the studies reviewed were quite different. That is, some studies investigated participants running, others walking and some utilised sandals while others used a canvas shoes. Furthermore, there were quite a variety of EMG parameters reported among these studies.

    I might add that our systematic review was a launching pad. I’ve been busy conducted a series of studies as part of my PhD to see if I could improve on the methodological issues identified in studies. We have a couple of papers currently in review with journals, both investigated tibialis posterior and peroneus longus (via wire electrodes); and tibialis anterior and medial gastrocnemius (via surface electrodes). We developed a foot screening protocol to identify suitable participants for these EMG studies (Open access paper - http://www.jfootankleres.com/content/2/1/22). The titles of the EMG papers are:

    1. Foot posture influences the electromyographic activity of selected lower limb muscles during gait

    2. Do foot orthoses change lower limb muscle activity in flat-arched feet towards a pattern observed in normal-arched feet?

    I’ll return for some more discussion when these papers are ‘in press’ – hopefully before the end of this year.

    Sincerely,

    George
     
  8. Mark, the key word that you have added is "net", the studies show a reduction in internal inversion moment. In other words, the external inversion moment provided by the foot orthoses, reduces the necessary internal inversion moment from the soft tissues, reducing the "work" required by the soft-tissues. That's the theory anyway, the questions arise when we then look at the EMG data and see that tibialis anterior (at least in some studies) is working harder in association with foot orthoses.
     
  9. George, thank you for your response. At the time of writing your systematic review, you obviously believed that the literature pointed toward an increase in tibialis anterior and peroneus longus activity in association with foot orthoses, otherwise you wouldn't have said it. Do you still maintain that view? Moreover, is your EMG research of these and other extrinsic foot muscles in harmony or at odds with the consistent observation of decreased internal inversion moment in association with foot orthoses?
     
  10. markjohconley

    markjohconley Well-Known Member

    Thanks Simon, if I wasn't an aging balding sickly heterosexual I'd be making advances. Would you know of any webpages for biomechanical terms, I've tried unsuccessfully, probably haven't used the appropriate keywords, thanks, mark
     
  11. Mark:

    After you have read up on inverse dynamics, then get back to us with more questions.
     
  12. markjohconley

    markjohconley Well-Known Member

    Thanks Kevin, "inverse dynamics", deriving the kinetics from the kinematics of bodies. Yep got to sit down for a few days with a drawing board handy. Started on a few webpages and was going OK till I came across ...

    Mzp = Iza - Mzd - Rxp.(yp-yCoM) + Ryp.(xCoM-xp) + Rxd.(yCoM-yd) - Ryd.(xd-xCoM)
    ..... from http://www.univie.ac.at/cga/teach-in/inverse-dynamics.html

    My confusion derived from the 'net' term in the Results of the abstract, and missing the 'internal' term, which Simon brought to my attention.
    Despite my biomechanical knowledge shortfalls I am following the discussion, as I attempt to with all the top threads.

    Incidentally, I query the link-segment model at this website in regard to the proximal ends of both thigh and shank, the moments should surely be Mzp.

    All the best, mark
     
  13. Mark:

    Do not worry, for the past 10 years I have been trying to impress upon my podiatric and research colleagues that if they do not designate which moments (i.e. internal versus external) they are talking about when they present a lecture or write a paper, then their research findings will mean nothing when presented. This is now a huge problem that most everyone seems to be ignoring, for whatever reasons. Inverse dynamics researchers standardly use internal moments, but we, as clinicians, use external moments when we talk about things such as rearfoot inversion-eversion moments.....they will be exactly opposite from each other!:bash::craig:

    When I find a little more time, I will write a more detailed note that better explains the problem.
     
  14. toomoon

    toomoon Well-Known Member

    very nice discussion lads.. and glad to see you championing the right s of moments kevin, whether they ber internal or external!

    thought I might change the subject a little and give you all a little food for thought.
    Just about to publish a new paper on gender research, the gist is as follows:

    Background: The relationship between the phases of the menstrual cycle and injury risk remains unclear. Previous studies indicate that neuromuscular function may be compromised during menstruation, which could result in reduced cyclicality of movement patterns.
    Hypothesis: Knee acceleration patterns during running gait will be more variable during menstruation when compared to ≈ovulation in women who do not take the oral contraceptive pill.
    Study Design: Controlled laboratory study.
    Methods: Thirty-six women (18 monophasic oral contraceptive pill users: MOCP group and 18 non-pill users: NP group) performed two, six minute treadmill running trials at 10km.hr-1 with a triaxial accelerometer fixed to the proximal tibia. These trials were performed at menstruation and ≈ovulation (or for the MOCP group at similar stages of the cycle) in a randomized order. The cyclicality of gross mediolateral tibial acceleration during 15 consecutive strides was assessed using combined wavelet and autocorrelation analysis. The regularity of vertical impact force transfer to the proximal tibia was assessed by comparing mean and standard deviation data across the 15 consecutive strides. Within-group paired-samples t-tests were performed to assess differences at each stage of the menstrual cycle (α = 0.05).
    Results: A significant difference was observed for both gross mediolateral accelerations and regularity of vertical impact force transfer in the NP group, with increased variability at the time of menstruation compared to ≈ovulation. No significant difference was observed for either measure in the MOCP group.
    Conclusions: Tibial accelerations during consecutive strides were more variable in the NP group at menstruation, and may be a result of compromised motor control strategies.
    Clinical Relevance: This study provides further evidence of variability in performance and motor control during menstruation, and may have implications for a female athlete’s risk of injury.

    what say you?
     
  15. So, anyway.... In the absence of any new insights, lets assume that the conclusion that George et al. made regarding tibialis anterior activity in the presence of foot orthoses is accurate. That is, the activity appears to be increased in association with foot orthoses. This would suggest that in order for the observation of decreased internal inversion moment in association with foot orthoses to be valid, the other muscles providing inversion moment must have decreased their activity. What if the patient has a problem with their tibialis anterior? Moreover, why would one of the supinators, i.e. tibialis anterior, increase it's activity, while the others decrease theirs? Could the manner in which inversion moment is calculated using an artificial axis along the midline of the foot account for errors in the observation that internal inversion moment has been reduced?

    The internal moment + external moment = net moment discussion is interesting. How does the body "know" that the external moment has changed and therefore it can reduce the activity of the supinator muscles? Kinaesthetic feedback and modulation would seem to be the answer- which inevitably leads back to the preferred motion pathway model. SO the question becomes, does the net moment change? Moreover, how do we measure the net moment?

    Why do we see an increase in peroneus longus activity with foot orthoses of the designs used in the EMG studies?
     
  16. Javier Pascual

    Javier Pascual Active Member

    Simon,

    I think I am bit late in this discussion but I will try to help... The point is that joint moments are calculated (by means of inverse dynamics) using the center of mass location of the segments, segmental masses, ground reaction forces and the angular accelerations of the segments.

    The moment calculated is the external moment, but some authors report it as the internal (or sometimes even muscle) moment simply by reversing the sign (+/-) in the data. It depends on the joint we are studing, i.e. in the knee joint moments in the frontal plane are usually described as external and in the foot they are usually refered as internal. That is the reason we used that convention in the paper. However from this discussion I have realized that probably it wasn´t a good choice and probably I will refer it as external moments in the future...

    Perhaps it would be less misunderstood to say that : "varus wedges significantly increased external ankle inversion moments" instaed of "varus wedges significantly reduced net (internal) ankle inversion moments". Because I am not sure that the first sentence means exactly the same (in clinical terms) that the sencond sentence... Perhaps increasing external ankle inversion moment does not necesarily mean that there exists a decreased ankle inversion moment, spetially from the muscles
     
  17. Javier, and my sincere apologies to Mark, as Javier's post has just made me go back to the top of this thread. I'd "read" what I assumed was being said not what was actually said: "varus wedges significantly reduced net ankle inversion moment". Now this is strange, as Mark had already pointed out- but I'd failed to see. If we are talking net inversion moment, why should varus wedged foot orthosis reduce this?????????????

    Javier, we must be very careful with our terminology here. So what the study actually demonstrated was that the net moment (external + internal) was changed, or just that the external moment was changed?
     
  18. But all of this still doesn't resolve this problem I have:
    Varus wedged foot orthoses increase the external eversion moment, or put another way they decrease the external inversion moment- right?

    So why does that increase the activity of tibialis anterior (and possibly other supinator muscles)?

    Within tissue stress theory, these supinator muscles should be required to do less work in the presence of a varus wedged orthosis. Yet the evidence, for tibialis anterior at least, seems to suggest that it is doing more work. This doesn't fit with tissue stress theory. Thus, the basic premise of adding external supination moment to reduce the force required by the tissues that can provide internal supination moment, appears flawed. Viz, tissue stress theory appears flawed, at least for tibialis anterior. :bash::morning::bang::craig: (that's not true, tissue stress theory is good, it's just that orthoses may not work within the confines of tissue stress theory)

    "Everything you know is wrong."
    "Stay asleep."
    "Watch more T.V."

    "They Live"- John Carpenter http://en.wikipedia.org/wiki/They_Live
     
  19. Javier Pascual

    Javier Pascual Active Member

    Simon,

    Yep, the terminology could be confusing in this regard. Internal moments are assumed to be generated by the muscles, soft tissues, and joint contact forces acting on the joint and are inferred from inverse dynamics calculations of external moments and angular acceleration of the center of mass (careful!!, it is not the joint aceleration; it is the acceleration of the center of mass of the segment, i.e. foot). From those data (external forces measured by a force platform and aceleration of the center of mass of the segment) you can infer the "net joint moment", which is usually referred for most of labs as "internal moment"

    The study showed that varus wedges reduces net ankle inversion moment (internal ankle inversion moment) calculated by a change external forces and acceleration of the center of mass of the segment.

    Cheers
     
  20. Varus wedged foot orthoses should increase the external rearfoot inversion moment, or put another way, should decrease the internal rearfoot inversion moment.

    By the way, the compression force within the sinus tarsi between the leading edge of the lateral process of the talus and the floor of the sinus tarsi of the calcaneus will cause a significant proportion of internal rearfoot inversion moment in the foot which reaches the maximally pronated subtalar joint positon in these studies. So, as Javier stated, it isn't just soft tissue tensile forces that cause these internal rearfoot inversion moments.

    Great discussion!
     
  21. Sorry, just realised I got my eversion and inversion the wrong way around!:bash:
     
  22. efuller

    efuller MVP

    I would imagine arch height of the orthosis could have a major impact on ant tib activity. If it was high it may uncomfortable to have a fast loading in the arch so a person could adapt by increasing ant tib activity so that forefoot loading (and arch loading) is delayed.

    The anterior tibial muscle has a much better lever arm to work as a dorsiflexor of the ankle joint. At the STJ, depending on STJ position, the Ant tib muscle can act as a pronator. So the different effects seen could be explained by moments at the ankle joint and not the STJ.

    Regards,

    Eric
     
  23. I tend to agree. I believe that this is one of the reasons we see variable outcomes in the EMG studies of this muscle in association with foot orthoses. Also that the devices may increase plantar flexion moment about the ankle- any data to support this contention?
     
  24. efuller

    efuller MVP

    No data. If the orhtotic shifted the foot anteriorly in the shoe the shoe contact point during heel strike would be further posterior to the ankle joint axis creating a greater external plantar flexion moment at the ankle. The greater external moment would require a greater moment from the ant. tib muscle to keep the same velocity prior to forefoot contact. It would be interesting to look at what point in gait the ant tib. activity increased. In gait, after the center of pressure has passed anterior to the ankle joint, ground reaction force will be causing a dorsiflexion moment at the ankle. Therefore there is no need for ant tib to be acting at this point in gait unless it alters foot comfort.

    Cheers,

    Eric
     
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