In a message dated 98-04-29 03:29:46 EDT, Keith Rome writes

> 
>  The stiffness instrument as stated previously has been calibrated and 
>  tested on 'healthy inviduals'. The problem arises from the raw data. 
>  We have used polynomial and splinic transformations of the data. But 
>  the question still arises what part of the force-displacement curve 
>  is important to clinicians. To scientists/bioengineers there is 
>  different interpretations. This is where problems arise. Any 
>  comments/suggestions.
>  
>  

A theory I have, and it may be a weak one, is that there are two kinds of
MECHanical heel pain.  The first, we all know and love is pain at the
insertion of the plantar fascia.  The second is a "bruising" type pain from
either people standing with more weight on the heel or from impact at heel
contact.  I'm not sure which.  Anecdotally, I have seen people with very
flexible feet stand with a lot more weight on their heel than average.  (80%
of weight behind ankle axis and a not very scientific average of about 60% of
weight on the heel)  Anyway, back to your question.  The bruising pain may be
related to the impact forces at heel contact and this would be attenuated by
the combined shoe hand heel pad stiffness.  This peak, in running, is directly
related to the vertical velocity of the leg and foot segment prior to heel
strike.  

Bobbert MF.  Yeadon MR.  Nigg BM.  Mechanical analysis of the landing phase in
heel toe running.  Journal of Biomechanics.  25(3):223 34, 1992 Mar.

 Bobbert MF.  Schamhardt HC.  Nigg BM.  Calculation of vertical ground
reaction force estimates during running from positional data.  Journal of
Biomechanics.  24(12):1095 105, 1991.

In guessing what kind of pathology could be related to the stiffness of the
fat pad I could see "bruising" heel pain and impact stress in structures up to
the knee.  But the forces above the knee are atenuated by knee flexion.   The
forefoot is off of the ground at the time that heel pad stiffness is important
so the only other structure that may be important would be the anterior tibial
muscle.  (Anterior shin spllints?)   Also, as you mention in your later post,
heel pad stiffness may be important for diabetic feet.

I hope this helps,

Eric

There has been a study that shows a change in the 


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