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Is The Ground Flat?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Graham, Oct 16, 2008.

  1. Graham

    Graham RIP

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    David Holland asserts that:

    What say our learned collegues
  2. From what I have seen over the past decade of reading notes on the Podiatry Mailbase and Podiatry Arena.......

    if David Holland is speaking.......

    there is a 73.9% chance that the words, "hard, flat ground", will somewhere be within the body of the posting.:deadhorse::deadhorse::deadhorse:
  3. davidh

    davidh Podiatry Arena Veteran

  4. DaVinci

    DaVinci Well-Known Member

    Surely that is because everyone has there own particular interests, there own particular areas of expertise. Whenever a topic comes up of relevance to that area of interest or expertise, they are more likely to comment on it?
  5. Craig Payne

    Craig Payne Moderator

    Surely the answer to this depends on the context of the question (or clinical problem).

    If the problem is an overuse injury in a marathon runner, then the shoe/foot interface is not "flat" (it has a 10mm heel raise in most shoes), but the interface between the shoe/ground is "flat" (assuming they run on the road and live in a flat area and do not hill work).

    If its a plantar neuropathic ulcer, then the overload of the tissues does not come from a flat ground as the ADL's carry carried out in a variety of surfaces and a variety of gaits (there was a good study on plantar pressures in diabetes a few years ago that compared straight line walking to walking in a figure 8).
  6. davidh

    davidh Podiatry Arena Veteran

    Hi DaVinci,

    Stating the obvious, but thanks for pointing it out;).

  7. markjohconley

    markjohconley Well-Known Member

    For most training that would be flat but not level due to the camber, no?
  8. Adrian Misseri

    Adrian Misseri Active Member

    But the foot really isn't flat now is it? :pigs:
  9. pgcarter

    pgcarter Well-Known Member

    What about timber industry workers or outdoor education teachers in the bush all day>?....And in the interests of even handedness I've observed that there is a 99.9% likelyhood of Kevin saying something about subtalar joint axis position or rotations if a topic having anything vaguely to do with that comes up. Which is not to be critical, just to state the obvious.

    regards Phill Carter
  10. True:D

    Also true:D

    VERY true. Its probably a heuristics thing.;)

    However. It seems that David is saying

    Anyhoo I'm absolutely serious when I say that the "basic interface between the shoe and foot" and the shoe and ground is not flat.

    I think this is, as always, a question with varied answers. However very few shoes are entirely flat inside and even fewer are entirely flat under the sole. Most shoes have moulded rubber soles which are generally pitched higher in the heel and are often rounded under the heels.

    I would suggest that very few outdoor surfaces are consistantly flat, even roads and pavements tend to have camber as mark points out.

    So my $0.02 is that it IS possible to find a hard flat shoe foot and foot ground interface, but it is far more likely to be the case that the foot will be inclined in the sagital plane by the shoe all of the time.

    It is interesting to note that since the popularity of those Friggin ballet pump slippery type girls shoe things i have seen a great deal more problems of the tendo achillies, severs and escape pronation. :craig:

    Read this sentance 3 times. still don't understand it! What is an ADL and what does it carry?

  11. Well, I think that 99.9% is a little high, but the point has been noted.......and then..... ignored....and then..... forgotten.;)

    If we are to go anywhere further with this discussion, we must first define what we mean by "flat ground" or "horizontal ground". Ground, like any three-dimensional (3D) surface, can be described many ways, using either relative or absolute values. If we were to show 1,000 people a photo of the top surface of a new wooden table-top, probably 999 of them would say that the table-top was "flat". However, now if we showed the same 1,000 people a scanning electron microscopic image of a section from that wooden table-top, probably 999 of them would describe this surface as "rough and uneven".

    Therefore, "flat", "uneven", "rough", "undulating", "sloped", "hilly", "cambered", "smooth" and other such terms used to describe the 3D shape of a weightbearing surface are all relative and subjective terms. None of these are absolute or precise terms. These words should not be used in a scientific discussion on the biomechanical effects of 3D weightbearing surface shape on the kinetic and kinematic function of the foot and lower extremity, unless we are to first define and agree to the same precise definitions for these terms.

    Once we all decide on how much angular slope a weightbearing surface can have from the horizontal reference plane and how much variation and irregularity of contour is allowed within a given weightbearing surface area to still call that same weightbearing surface "flat and horizontal", then we can all begin to have a meaningful discussion.:drinks
    Last edited: Dec 17, 2008
  12. Took the words out of my mouth. I was going to say that we can look at macro and micro. What shape is the earths surface when we look at it from the two extremes?

    As I have noted before, my view is very much in line with Roberts.
    Last edited: Dec 17, 2008
  13. markjohconley

    markjohconley Well-Known Member

    Activities of Daily Living, and yes
  14. Hmmm. An annoyingly good point as always. Since the man himself in person has not come on to give an answer i'll have a crack.

    For the purposes of this discussion is the significant element to this question. As Kevin points out depending how fine a detail we look no surface will ever be entirely flat OR level.

    There are also 4 elements here. Angulation and irregularity, foot-shoe and shoe-ground. Irregularities which are larger than the foot become angulations.

    Irregularity shoe-ground

    I would say that for this to be significant in context of what we do (ie clinical applied biomechanics) an irregularity must be sufficient to either incline the foot in any direction (see below), deform the shoe sole, or create a rocker effect in any plane. Obviously this is heavily dependant on the style of shoe. For deformation of the sole of the shoe i suggest anything the patient can detect in superficial sensation (like the bumps on zebra crossings) are significant.

    Angulation shoe-ground.

    Our threshold of repeatability for most lower limb goniometry is pretty large, around the 5 degree mark or more depending on what study you look at. I therefore offer that for this debate we consider any angulation greater than 3 degree significant. Most orthotic modifications go to a much finer detail than this (it cracks me up when i see a prescription for a 3.5 degree wedge). But i question the real world relevance of any angulation or wedge less than a couple of degrees.

    Angulation in shoe.
    As with ground i question the relevance of anything less than 2 or three degrees. 3.5 (Its how it comes!) is the smallest wedge i use in orthotics so IMO this is a reasonable sort of threshold.

    Irregularity in shoe.
    This is a tricky one because it is not a simple question of vertical force. The way the shoe flows into the sides is also significant as is the degree of compressibility / conformibility of the sole. Can't really think of a rational way to set a tolerance threshold for this one. Anyone?

    Obviously no threshold is perfect. If anyone else can offer a better idea then lets hear it!


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