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Heel strike subtalar joint pronation shock absorbtion

Discussion in 'Biomechanics, Sports and Foot orthoses' started by wdd, Jun 5, 2012.

  1. wdd

    wdd Well-Known Member

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    At heel strike subtalar joint pronation produces shock absorbtion.

    Over the years I have seen this statement written time after time as if it's a self evident but so far I haven't seen an explanation, ie what about subtalar joint pronation absorbs ground reaction force at heel strike?

    My own rationalisation is that the vertical reduction in the apparent height of the calcaneum associated with pronation gives that extra vertical height for the body to be decelerated. But surely the difference in the apparent height of the calcaneum at heel strike and following STJ pronation is so little that it can't make much direct, practical difference to shock absorbtion?

    Thanks in anticipation.

  2. Craig Payne

    Craig Payne Moderator

    I vaguely recall 2 studies from >10-15yrs ago that does not support the statement.

    If I recall correctly, one study looked at impact with and without strapping to limit STJ pronation and found no differences. The other study (I think) looked at impact under the foot running on a camber (ie the 'downhill' foot supinated more and the other pronated more) and found no differences in impact forces between the two feet.
  3. Griff

    Griff Moderator

    Some articles for those interested on the subject:

    Attached Files:

  4. efuller

    efuller MVP

    I've seen a lot of slow motion videos of heel strike in walking. Most of them, you see very little internal leg rotation between the time of heel contact and forefoot contact. After forefoot contact you do see rapid internal rotation of the leg relative to the foot. This makes sense mechanically as the center of pressure under the heel, during the time between heel contact and forefoot contact, will be relatively close to the STJ axis and therefore not cause much moment. After forefoot contact, assuming lateral contacts first, the center of pressure will shift more lateral and cause a greater pronation moment. So, the STJ doesn't really pronate during the time heel contact "shock" needs to be absorbed. After the forefoot is fully loaded there is body weight, but there really isn't any shock.

    To absorb shock you need to have motion resisted by muscle action. In heel contact gait, I can see ankle plantar flexion resisted by the anterior tibial muscle reducing shock, but not really STJ motion.

    The rigid lever mobile adapter theory doesn't really stack up to observation.

  5. Dananberg

    Dananberg Active Member

    I have longed viewed STJ pronation at heel strike as more of a rotational accommodation to internal limb rotation, knee & hip flexion which occur at this time in the step. Eric was, of course, correct in that muscle firing must occur to decelerate the various components for shock attenuation to occur. So, at heel strike, gluts fire to prevent hip collapse while the quads fire to prevent knee collapse. Pronation of the STJ permits matching of these motions from above to a motion the foot can manage considering its small mass as related to the remainder of the lower extremity.

    Of interest, for instance, when the hip extends during the 2nd half of single support phase, the gluts are “off”. Muscles, when acting eccentrically (resisting motion), are far more efficient than when firing concentrically (creating motion). It has been my long term view that these principles are critical for understanding the efficiency of the gait cycle.


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