Chuckie (www.chuckiev.blogspot.com) just wrote about one of his epic rides of maintaining 100RPM for 1 hour.  Well it was my turn to attempt this on the PCs.  I lasted 20minutes!  It is one thing to spend time on the cranks, but another to try and maintain a high RPM.  This is definitely something I need to work on.  All the muscles you can think of were firing.  I can only question the benefits while I am doing it, but now after a few days I already feel refreshed and ready to tackle them again!