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The Initial Windlass Phase of Gait .

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, May 30, 2020.

  1. scotfoot

    scotfoot Well-Known Member


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    Here is a brief video explaining the Initial Windlass Phase of Gait . The load sharing mechanics of this mechanism where first described by me , here on this forum in conversation with Dr Eric Fuller ,some time ago .

     
  2. scotfoot

    scotfoot Well-Known Member

    Imagine walking for a prolonged period in shoes that have a shallow toe box . The toe dorsiflexing action is impeded and this might lead to pain on the top of the foot or in the lower leg .

    Solution ,shoes with a deeper toe box or easily displaced upper made of a mesh type material .
     
  3. scotfoot

    scotfoot Well-Known Member

    So a shallow toe box would inhibit the dorsiflexion of the toes prior to foot strike and adversely affect the initial windlass phase ( IWF) .

    Another feature of modern shoes which might interfere with the IWF is the toe spring . Obviously , if a toe spring is present the toes cannot fully plantar flex during weight acceptance and so the IWF is suppressed.

    Imagine a car driving at 40 mph into a brick wall. The deceleration is near instantaneous and the result is great damage to the car and the crash test dummy inside . But put a wall of tyres in front of the brick wall and the rate of the deceleration of the striking car is greatly reduced .
    Even small time diffrence in rate of deceleration can have a big impact on the damage the sudden release of kinetic energy can have especially over many foot strike repetitions .
    It is speculative , but re-educating the foot and allowing it to function properly in terms of the IWF , might have a huge impact on the course of foot pathologies such as plantar fasciitis .

    Gerry
     
  4. scotfoot

    scotfoot Well-Known Member

    What evidence is there for purposeful pre strike dorsiflexion of the toes during barefoot walking ?

    A paper produced in 2009 by Carvaggi et al look into exactly this aspect of unshod gait . They found that on average the toes were dorsiflexed about 30 degrees at heel strike .
    Their conclusion was that this gives a pretensioning of the plantar fascia .

    Extract from paper conclusion

    "Indeed, a recent study has proposed that early stance preloading of the PA may be beneficial to propulsion during walking (Pataky et al., 2008). While the present study strongly suggests that such preloading exists, without further experimental and/or modelling studies, we can only speculate as to the possible advantages of such preloading. Loading the PA at heel-strike is likely to reduce the crimp present in unloaded collagenous tissues (Butler et al., 1978), thereby resulting in earlier arch stiffening and helping to ensure that, as the propulsive phase begins, a greater proportion of force is transferred by the foot to the ground."

    In my opinion the authors did not fully understand the physics involved here since as I have described elsewhere, dorsiflexion of the toes prior to heel strike is not about the fascia being readied to take on load more instantly but exactly the opposite. That is if it is wound around the MTFJ it can then be paid back out like arrestor cable in an aircraft carrier .

    That it still mechanism persists in a group of twenty somethings used to wearing restrictive footwear merely demonstrates how vital this mechanism is in normal gait .

    Paper from Carvaggi

    A dynamic model of the windlass mechanism of the foot: evidence for early stance phase preloading of the plantar aponeurosis
    Paolo Caravaggi, Todd Pataky, John Y. Goulermas, Russel Savage, Robin Crompton
     
  5. scotfoot

    scotfoot Well-Known Member

    At heel contact during walking the tibialis anterior muscle is active . It is thought that the muscle acts eccentrically and helps prevent the foot "slapping" into the ground producing foot pain .
    The extensor hallucis longus can act in much the same way ,but since it crosses the MTPJ it also acts eccentrically to assist with both preventing foot slap and excessively rapid loading of the plantar fascia and tissues of the foot through the initial windlass phase.
    Footwear does not generally prevent the tib ant from doing its job but from the nursery to the grave footwear will inhibit the the extensor hallucis longus.

    I read a study that demonstrated little activity in the flexor digitorum longus at heel strike in a western population and this may be because of the effects that footwear has on early neural development . Splinting from an early age if you like .

    I am not that well versed in the specific techniques used by Prof Irene Davis at the Spalding Institute but can see the potential benefits of trying to breath life back into the initial windlass phase .

    Gerry
     
  6. scotfoot

    scotfoot Well-Known Member

    The extensor hallucis longus then ,acts eccentrically at heel contact and applies a dorsiflexing moment at the ankle preventing foot slapping .

    With the heel and forefoot on the ground ,the dorsiflexed toes then lower in a controlled fashion ensuring progressive loading of the PF and tissues of the foot .
    But what of shoes with toe springs . The toes cannot flatten against the substrate in the way they otherwise would potentially leading to excessive peak load .
    With regard to transitioning to a barefoot , forefoot strike , the initial phase of gait (IWP ) becomes even more important .
    If suppressed during developmental stages it may be difficult to establish natural range of motion and motor patterns in later life .
    Thus , although barefoot running may be seen by some as a more natural state of affairs than running shod , changing to this style of running may simply not be a good idea for many/ most from a habitually shod background .
    A heel strike in a cushioned shoe may be more protective of the plantar fascia than a barefoot , forefoot strike with a reduced level of IWP.
     
  7. scotfoot

    scotfoot Well-Known Member

    During weight acceptance when walking, the foot lengthens and the distance between the heel and the met heads increases . The plantar ligaments take much of the load . But what if the toes are held in an extended position by a toe spring .
    The PF stays wound around the met heads and so it takes more of the load than it might otherwise do . Yes ?
     
  8. scotfoot

    scotfoot Well-Known Member

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