I like cardio all the time!! here is my thoughts!
#1 YOU will NOT lose muscle mass if taking the right amount of proteins, doing the cardio at the right heart rate and right times ie; first thing in the am (after 40 gm of protein) or after my training workout. you might drop some water, and your scale weight may drop a bit...but none of us get caught up in what the scale says ..do we??? he he so keep in positive nitrogen balance, ie; protein and you wont lose muscle. dont confuse water mass w/ muscle!!
#2 youre on a cycle, even if youre afraid to lose mass, do some!!
why? because the increase in blood flow and circulation that comes from it!
key word...blood flow!!! yeah, that stuff that courses thru the veins and transfers toxins/ waste and other debris from the metabolic process right out of your system!! you will get more oxygenated nutrient enriched blood heading to those just worked body parts , that will give you better recoup time, less (lactic acid) soreness... better growth!!
ok...enuf of my babbling, do your damn cardio and grow!!!!