Weight lifting during water fast

Today is my first day of a long water fast. It's going to be somewhere around 30 days long. I know that I shouldn't lift weights a lot during my fast. My question is let's say I train shoulders during my fast. Will my body breakdown other muscles to repair the shoulder muscle/help it grow? Since that's the only place amino acids are really available? I've read this once before but can't remember where and was wondering if it's accurate? Thanks! Tweet