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Different orthotics stiffness for winter and summer

Discussion in 'Biomechanics, Sports and Foot orthoses' started by mike weber, Nov 11, 2009.

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    Had a patient in before with 3 "different" devices for everyday use, running and sking.

    He got a bit confused when I asked what the differences were as they looked the same to me and felt the same to him anyway... Having moved from a more constant climate of OZ. To the less stable climate of Sweden there is a call for two different stiffness of orthotics for warm and cold activities ?

    Yes I realise that the bodies temp is pretty constant but if there is snow and minus 28 c cold then the plastic with be more stiff does anyone think this is significant?
  2. As we don't fully understand the significance of orthoses stiffness yet it difficult to give a definitive answer. However, I would assume that the variation in "working" temperature at the foot- orthosis interface would have minimal effect.
  3. ok I might do an experiement when /if we get a really cold day with a pair of running shoes and therometer go out walking and measure the temp under my orthotics and report back
  4. Measure external temperature, then measure temperature of orthosis at foot-orthosis interface during given activity in extremes of temperature. Then show temperature effects of any recorded differences on load-deformation of orthoses. THEN, show effects of any variation in load-deformation characteristics on kinetics /kinematics; then show influence of any kinetic /kinematic difference on clinical outcomes. That should keep you busy for the next few years.
  5. I believe I´ve just been Spoonered :D

    I´ll start with baby steps 1st before taking it to the next level
  6. pgcarter

    pgcarter Well-Known Member

    Sounds like you are inventing a solution for a problem that does not really exist.... I'm happy to support the idea that different acitivities may require different orthoses shape or materials......but not temperature, the homeostatic nature of human bodies......frost bite etc the actual temp range inside the footwear is not that large and a ten or 20 deg effect on the materials is going to be really quite small....but good luck
    regards Phill Carter
  7. Agreed, but the patient in question obviously fell for it!
  8. Thanks for the reading Simon.

    Clearly as you and Phil said there will be a rise but nothing that will have a major effect on device stiffness. The china leather article talked about 6 degee which then become stabil after a short time. Nothing to consider.
  9. Speaking from experience of doing multiple sports in the snow including cross-country skiing, downhill skiing and snowmobiling over the past 30 years, the temperature of an orthosis in snow activities does become quite colder than the foot. This would certainly affect the orthosis stiffness, with increased stiffness in colder temperatures in especially the shank independent materials such as polypropylene. Colder temperatures can even lead to increased fracturing in the acrylic materials such as Rohadur. I'm certain that some individuals could easily feel the difference in stiffness of their orthoses with a 50 degree temperature change. That being said, I have never seen anyone have an orthosis just for cold temperatures, but rather I seen multiple patients that have separate orthoses for the specific sport that is used in cold temperatures such as cross-country and alpine skiiing.
  10. pgcarter

    pgcarter Well-Known Member

    I tend to think that if the temp really got to -20 deg C inside a boot for very long the foot itself would not be doing too well, it would not be just the orthotic going rigid......... and even then the change from normal room temp is only 40 deg or so, when I did a little research project on hysteresis, elastic vs permanent change, on rubber bands even at 90 deg C. you could demonstrate an effect....but only a small one, so a forty deg change on polypro I would have thought would be less effect. I can vouch for the effects of severe temp changes.....-30 deg at the highest resort in Colorado....the quality of circulation was a bigger issue than the temp alone.....some people get numb toes and others don't. I got numb halluces until I expanded the boot toe box for greater height....after that the temp did not seem to matter.
    regards Phill Carter
  11. joejared

    joejared Active Member

    (acetal) Delrin would likely be a better candidate for a more constant flexibility at more extreme temperatures, and teflon would probably be even more consistent in this area, and both materials would need to be considerably thinner to match flexibility of polypropylene type devices. I'd also suggest avoiding abs plastic, as it's more brittle at colder temperatures.

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