Hi Stanley and all
Stanley wrote in response to my comment:
>>To answer your question: the magnitude of force or body weight is not
>>changed, but the point of application of that force is changed. When the
>>point of application of the force is changed the moment arm (R) that force
>>has about an axis is changed. So R changes even though the position of the
>>calcaneus does not. The concept of center of pressure may be helpful in
>>understanding this...........After standing on a varus wedge, the position
>>of the force is
>>different even though the position of the foot did not change.
>
>Eric, I thought I had this concept, until you talked about the varus wedge.
>How is the position of the force different on a varus wedge?
As you lower feet on to a varus heel wedge the medial side contacts
first. A lot of feet will not change their calcaneal heel bisection
position when they stand on wedges. The part that compresses first will
have higher pressure and more force under it. So when the foot is fully
lowered on to the wedge the higher side of the wedge will have more
pressure. I have some unpublished data on this. There are also studies
done recently looking at moments with wedging and there have been changes
that correlate with the center of pressure being shifted toward the high
side of the wedge.
The location of force can change without a change in position.
Cheers,
Eric Fuller
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