SS, this topic has been beaten to death..i for one can not get away with anything but am cardio and i never lost any muscle last time and dropped from 282lbs to 227lbs in 8 weeks...while some can do the same doing pm cardio only, i cannot...I believe iyt is a personal thing and needs to be determined by the person, and there is no right and wrong answer to this question, steps can be taken yto stay anti-catabolic before am cardio and that is essential to doing it right...
here is a like to about 6 pages of arguments from a bunch of us on the topic, skim it over and see what you think
http://forums.steroid.com/showthread.php?t=240522