Originally Posted by jur
Quoting from
http://www.sheldonbrown.com/standing.html:
"The added stress flexes many parts of the bicycle, and the energy required to do this flexing is not usually recovered when the parts straighten back out."
I sort of passed high school physics, and that doesn't make sense to me: the energy put into the system can't just be "lost", it either is there or is converted to another form. Unless your bike parts are heating up or giving off light, the energy is still there, no?. I think the difference between rigid and flexy parts and frames is the speed and/or "feel" of how the energy is fed back.