In reply to IanF:
I know why I take protein before, during and after a workout, however cannot provide you with sound science based advice.
As I understand it the muscles need protein when forced to contract if this is not freely available then the body turns to the next source, the muscle fibers.
Personally I take leucine, isoleucine and valine along with a few other funky products as a pre-work drink (30mins prior). During a work out I take more protein usually essential amino acids and post exercise a mix of EAA's with extra L-Glutamine.
This article might help...
http://www.t-nation.com/free_online_article/most_recent/maximize_protein_sy...