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Significance of hip rotators

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Robertisaacs, Nov 14, 2008.

?

The external hip rotators probably play only a minor role in generating STJ supination moment in mos

  1. Agree

    11 vote(s)
    73.3%
  2. Disagree

    4 vote(s)
    26.7%

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    Kevin said

    Agree or disagree?

    Regards
    Robert
     
  2. Robert:

    What is a mos? A new species of animal??;):pigs::pigs::pigs:
     
  3. blinda

    blinda MVP

    :D:D Am also wondering what a `mos` is?

    cheers,
    Bel

    l

    Ahh, just read this. Sorry `nother blonde moment!
     
    Last edited: Nov 14, 2008
  4. A mos is a mythical creature . Little is known of it save that some think hip rotators play little part in supination of its stjs.
     
  5. DaVinci

    DaVinci Well-Known Member

    If you were to run this poll on a physiotherapy site, it would almost all be 100% for disagree.
     
  6. efuller

    efuller MVP

    Agree, because of Newton's third law. If the trunk applies an external roation moment to the thigh then there is an equal and opposite moment from the thigh applied to the trunk. In late stance phase the moment on the trunk would attempt to move the trunk in the opposite direction needed for forward progression. The trunk is up there in space not connected to anything when the other leg is in swing.

    Another reason: The old trick that Root Orien & Weed mentioned in their books about twisting the hips to cause a change in STJ position. If you have a person who is skinny enough to see the tendons contract, you will see the leg muscles PT and peroneus brevis contract when you twist your hips. If you are aware enough to not use your lower leg muscles and you try to twist your hips the STJ won't move much.

    Cheers,

    Eric
     
  7. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Resistance training is accompanied by increases in hip strength and changes in lower extremity biomechanics during running.
    Snyder KR, Earl JE, O'Connor KM, Ebersole KT.
    Clin Biomech (Bristol, Avon). 2008 Nov 13. [Epub ahead of print]
     
  8. Ian Harvey

    Ian Harvey Active Member

    If the rearfoot inversion moment decreased by 57%, then , on the face of it, this seems significant.

    I can't judge the relative contributions of the various muscles to pronation control, but the external hip rotators are relatively quite large, and the femoral head and neck may offer a larger lever arm than the lever arm around the subtalar joint?

    Can't comment on the effectiveness of the angle of their action relative to the hip joint axis.

    If their results are genuine (and there isn't an obvious reason why they should not be), then this might be an explanation?

    Eric says: Agree, because of Newton's third law. If the trunk applies an external roation moment to the thigh then there is an equal and opposite moment from the thigh applied to the trunk. In late stance phase the moment on the trunk would attempt to move the trunk in the opposite direction needed for forward progression. The trunk is up there in space not connected to anything when the other leg is in swing.

    Wouldn't the forward momentum and inertia of the larger trunk resist the closed chain moment from the thigh (at least to some extent), making it more likely that the thigh would externally rotate and increase the supination moment upon the foot?

    Apologies if I don't use correct engineering terms.

    Cheers,
    Ian.
     
  9. efuller

    efuller MVP

    Hi Ian,

    Yes I agree that the forward momentum and inertia of the trunk would resist the moment from the leg. The question, is this what you want to do? Do you want to slow the momentum of the trunk to supinate the STJ? If the goal is forward progression I would suggest that is not what we want to do. It is possible, but is it the goal.

    Another thing to think about is the connections from the thigh down to the subtalar joint. If an external rotation moment is applied to the thigh, the thigh will apply an external rotation moment to the lower leg through the knee. The knee structures are not arranged to transmit this moment well. I haven't thought much about which muscles would provide support to the moment. It might work, but the passive structures are not in the correct direction to prevent external rotation of the thigh relative to the lower leg. The lower leg has to transmit the force to the talus. Maybe, the ankle mortise is strong enough to transmit the stress.

    Cheers,

    Eric Fuller
     
  10. Ian Harvey

    Ian Harvey Active Member

    Hi Eric,

    Eric says"Yes I agree that the forward momentum and inertia of the trunk would resist the moment from the leg. The question, is this what you want to do? Do you want to slow the momentum of the trunk to supinate the STJ? If the goal is forward progression I would suggest that is not what we want to do. It is possible, but is it the goal.

    Doesn't the external rotation moment on the femur at the correct time in normal gait, cause supination of the foot and allow easier forward progression via the ankle and forefoot rocker mechanism? (I hope I have understood this). Could weaker external rotators cause a reduction in the efficiency of this mechanism, and conversely, might stronger external rotators improve this mechanism?

    Eric says: Another thing to think about is the connections from the thigh down to the subtalar joint. If an external rotation moment is applied to the thigh, the thigh will apply an external rotation moment to the lower leg through the knee. The knee structures are not arranged to transmit this moment well. I haven't thought much about which muscles would provide support to the moment. It might work, but the passive structures are not in the correct direction to prevent external rotation of the thigh relative to the lower leg. The lower leg has to transmit the force to the talus. Maybe, the ankle mortise is strong enough to transmit the stress.

    Can't comment on the strength of the connections between hip and foot. Perhaps the external rotators are not only stronger, but have been quite extensively "trained" over the research period, and are better at co-ordinating and timing the events of the leg?

    Also, the IT band does connect the bum to the tibia. It's external rotation properties upon the lower leg are not clear to me, but I have just looked at Primal Anatomy and seen that the IT band appears to connect to tib ant via the fascia around the knee. If the bum tightens the IT band, and tib ant fires soon after, this may cause more supination at the right time? Don't know, just speculating.

    I suspect that the external rotators do have some effect, and this could add to the efficiency of the foot position in gait?

    Don't know, just speculating. But, they are reporting significant results. Are these likely to be false or misleading?

    Cheers,
    Ian.
     
  11. efuller

    efuller MVP

    We would have to look at inverse dynamics to see if the trunk actually does apply an external rotation moment to the thigh. Yes, it could occur at the right time, but we don't know that it does and it would probably be variable across people if it did.

    I'm not sure what what the conection of hip moments are to the ankle and forefoot rocker mechanism. I'm assuming that you are referring to sagittal plane progression of the trunk that is allowed by closed kinetic chaing ankle dorsiflexion and the foot pivoting at the distal ground contact point when the heel lifts. These events are not necessarily conected with hip moments. If your point is that supination will make those pivots easier, then I would agree. However, that does not necessarily mean that the supination moment at the foot has to come from above. The Windlass and the posterior tibial muscle are things that have a direct effect on causing external talar rotation.

    The IT band is vertical. If you wanted to prevent transverse plane rotation of the femur on the tibia you would want horizontal fibers.

    I agree that it is possible for the external rotators to help supination. However, if I were going to expend energy to supinate the STJ I would use the posterior tibial muscle.

    Another thought. When we see late stance phase pronation, what is happening at the hip?

    The results of the paper showed increase in strength of the hip external rotators and they also showed that there was less STJ pronation. They did not show that hip rotators caused STJ supination. Correlation is not causation.

    Regards,

    Eric
     
  12. Ian Harvey

    Ian Harvey Active Member

    Thanks for your reply Eric,

    I had looked for a full text paper on this research earlier, but the link didn't work, and I couldn't get it by other means. I now have it and have skimmed through it briefly.

    The closed chain strength training protocols could have increased the strength of the tib post, along with the targetted hip rotators. Therefore, it can't be accepted that the increased strength of the hip rotators is the only factor effecting supination.

    Their figures do indicate that the calcaneus is significantly more inverted at heel strike, but we can't assume that the hip rotators are the sole cause of this.

    Cheers,
    Ian.
     
  13. efuller

    efuller MVP

    Actually, the hip rotators cannot supinate the STJ in swing phase. The foot as a whole would externally rotate. For the hip rotators to supinate the STJ the foot has to be on the ground. It does sound as if the increased supination could have been caused by incrased PT strength.

    Cheers,
    Eric
     
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