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Bojsen-Moller -low gear, high gear the new/old black ?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by mike weber, Nov 25, 2010.

  1. Bojsen-Moller's idea that there is possibly a "high-gear" or "low-gear" for propulsion in the human foot is an interesting one. However, I believe this idea of a "high-gear" or "low-gear" propulsion oversimplifies the complex processes occurring during late-midstance and propulsion that may cause propulsion over either the medial or lateral forefoot.

    Factors such as the prevailing subtalar joint (STJ) moments during late-midstance and propulsion, medial column vs lateral column dorsiflexion stiffness, relative length patterns of the metatarsals (i.e. metatarsal parabola), angle of gait and muscle strength may all influence whether the medial or lateral metatarsal heads are more involved in propulsion. I really can't see that using Bojsen-Moller system of classifying propulsion into two types is really any better than those clinicians that recommend "foot-typing classification systems" where they pigeon-hole feet into discrete anatomical classifications which may or may not have any correlation to foot function or foot and lower extremity pathology.

    I have never used Bojsen-Moller's ideas in any of my lectures (that I can remember), don't intend to but think that they may deserve historical mention by some lecturers. However, I don't think these ideas really belong in any state-of-the-art podiatric biomechanics lectures. I am not that sure that his ideas have helped me in any way to better understand foot function.
     
  2. Graham

    Graham RIP


    When you see the wear on an insole of a shoe from fifth met head through second to IPJ of the hallux, what does that indicate that is happening to the forefoot loading during propulsion?
    __________________
     
  3. Graham:

    Wear on an insole generally indicates the insole is receiving significant compression force from the plantar foot. Maybe you can elaborate further?:confused:
     
  4. Graham

    Graham RIP

    Kevin,

    See attached doc. 5th met to first ipj = low gear

    1st met through second met = high gear

    Perhaps!
     
  5. Graham

    Graham RIP

    Kevin,

    See attached doc. 5th met to first ipj = low gear

    1st met through second met = high gear

    Perhaps!
     

    Attached Files:

  6. Graham, you're surely not serious with that evidence?:morning:
    we really need Henenfeld's papers here to get a full historical, if anyone could oblige I'd be eternally grateful. Eric Lee sent me photocopies of these papers many years ago, I know I no longer have them.

    http://www.ncbi.nlm.nih.gov/pubmed/13053183
    http://www.ncbi.nlm.nih.gov/pubmed/13053190
     
  7. Graham

    Graham RIP

    Not at all. Just pointing out that if you take a look at the innersoles of shoes. If you make a full length orthoses and take a look at the forefoot wear after a number of weeks. You can, more often than not, make out wear patterns that "could" be explained utilizing Low gear/high gear principles.

    Although I'm sure they could be explained by a whole number of other principles. MASS perhaps. In fact, I bet if you look at the forefoot wear after wearing a MASS device you would very clearly see a "low gear" pattern. - perhaps
     
  8. Graham:

    Like you said, perhaps these insoles indicate a "low-gear pushoff". Maybe, also, these insoles demonstrate a functional hallux limitus, structural hallux limitus/rigidus or some other pathology since shoe insole impressions don't allow us to see the temporal patterns of ground reaction forces in the forefoot. An in-shoe pressure measurement system, such as F-Scan, would give you much more data that would allow a better classification of propulsion types in individuals.
     
  9. Graham

    Graham RIP

    I "believe" that low gear push off would indeed be a compensatory effect of a functional hallux limitus, structural hallux limitus/rigidus or some other pathology - perhaps!
     
  10. This is where 'current concepts in podiatric biomechanics' becomes difficult. Having sat through a couple of days listening to Craig's summarisation in the Boot Camp - of how the various axis determine the efficiency of low gear and high gear propulsion - and appreciating the logic - then reading this interprettion and also appreciating its logic, one is left with the overwhelming urge to inset the cranium into the microwave and cook on full power for 30 mins in the hope that whatever is left can make sense of it all. One thought though - if MASS orthotics aim to promote the foot to function in a supinated position primarily, doesn't that mean that function revolves around the low gear hypothesis - ergo; the least effective and/or optimal position for propulsion? :bang::bang::bang:
     
  11. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    MASS brings the first ray down to the ground, so that probably does not happen.

    Bojsen-Mollers hypothesis is just that. A hypothesis. IMHO, a very good hypothesis. It does explain a lot of observations and research on foot function.

    Maybe the use of the terminology of "high" and "low" gear as analogous to the gears in the car is problematic. Perhaps the focus and terminology should be on the length of the lever arm to the oblique and transverse axes.
     
  12. The length of the lever arm to the Achilles? Is it not the distance from the Achilles to the centre of pressure at any given time during propulsion which is significant here?
     
  13. Simon:

    Have to say that I have been smiling and laughing uncontrollably at times at seeing you, Eric, Robert, Graham and Michael all taking big bites out of The Turkey over the Thanksgiving holiday...you know who I mean.:rolleyes:

    Anyway, back to Craig's take on low-gear and high-gear. I agree with you that analyzing the center of pressure (CoP) makes a lot more sense than even trying to pidgeon hole the latter half of stance phase as being either "high-gear" or "low-gear". Certainly we would want to be able to classify the movement of ground reaction forces during the latter half of stance phase into more than just two categories, "low-gear" and "high-gear". I would think position of CoP relative to the ankle joint axis, subtalar joint axis and Achilles tendon would give us a more better idea of the kinetics of the latter half of stance phase than using Bojsen-Moller's "low-gear, high-gear" approach.
     
  14. Graham

    Graham RIP

    Careful Kevin! I could get charged with hunting "Turkey" out of season! :drinks
     
  15. That's the thing about turkeys - they often like to claim that they're really something else even when it's patently obvious that they're not.... ;)
     

    Attached Files:

  16. This is interesting from the Nigg paper Ian linked to here: http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=182059&postcount=26

    "Bojsen-Moller (1977) indicated that the MP joints rotate
    about a transverse axis for sprinting but an oblique axis
    during running. During running, the more anterior positions
    of the MP axis at the center and medial side of the
    foot would shorten the lever arm of the external ground
    reaction force and, therefore, reduce the calculated MP
    torque. The extent of the error associated with assuming
    a transverse axis would depend on the individual anatomy
    of the subjects. However, as was seen by the sensitivity
    analysis, an average anterior shift of the MP axis by
    1 cm resulted in an average decrease of 27% in the energy
    absorbed at the MP joint during running."
     
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