On Mon, 8 Jan 2001 14:16:05 -0800, Wally Day <[log in to unmask]> wrote:

>Does anyone have an understanding of how and/or why
>weight bearing exercise can increase bone density? I
>understand how muscle mass in increased (damage to
>muscle cell, body repairs and overcompensates - a
>simplistic explanation), but that doesn't seem to
>relate to bones.

I did my own google.com exercise and found:

      http://www.nationalacademies.org/ssb/csbmch6.htm

Read the "Putative Mechanisms" section and stuff like:

   "A recent mathematical model
   attempted to quantify the relationship between fluid shear stress on the
   extracellular surface and the increased calcium permeability of
   stress-gated ion channels in endothelial cells."

Is this any better?

It seems that there is also the inverse: losing bone density in
weightlessness.

Philip Thrift
http://www.paleofitness.com