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