Bruce,
Thanks for clarifying things.
You are alluding to hip swing as the means of lengthening the stride. Hip
swing lengthens the leg at contact and propulsion so the center of gravity
does not drop as much. What about hip extension? Isn't this the more
important factor for stride length? I can see how hip swing needs to be
increased with hip extension to keep the center of gravity from dropping
too much.
By the way, I wrong, and I appreciate you straightening me out. I was
looking at the foot and forgot about the hip.
Sincerely,
Stanley
At 08:04 PM 12/14/04 -0600, you wrote:
> Stanley asked last week:
>What I am asking is does the increased stride length from a valgus fore
> > foot post result from:
> > 1. An increase in firing of the gastrocnemius (as Kevin suggests).
> > 2. Or an increase in midtarsal pronation so there compensation for the
> > ankle joints sagittal plane motion, and hence a longer stride length.
>You have answered that with a shorter midstance, there is less MTJ
> > compensation, more foot stability and a longer stride as a result of hip
> > extension (and 1st MPJ dorsiflexion).
> > So you are saying that MTJ pronation limits hip extension. Can I assume
> > this is because external rotation of the femur allows for more hip
> > extension? If this is correct, then forefoot valgus posts would have to
> > work by causing more external rotation of the femur. Is this what you see?
>
>I would have to agree with Stanley here. There is no doubt in my mind that
>MTJ pronation limits hip extension. Since extension of the 1st mpj allows
>STJ supination, when timed properly, this will match the intenal rotation of
>the swing limb and cause external rotation of the lower extremity, including
>the femur, causing external rotation and a longer stride length. In my
>mind, this action facilitates the function of the GS complex, not the other
>way around.
>I hope this clarifies things.
>Sorry for the delay.
>Sincerely;
>Bruce Williams
>
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