I aim at losing fat. I find that if I do any more than 30min early in the season, I start losing muscle definition and I look flat. I am not extremely muscular, but I like to hold onto my hard earned muscle...hehe! Anyway, INTENSE INTERVALS of 20 mins(warm up 5 cool down 5-10) really kick my ass and burn fat! You really have to work hard...I almost feel sick at some points. I always do cardio after weight training (except for leg days) about 4/week.