I've decided that I need to start getting more serious about the cardio part of my workout. Previously I have only done 5 min set at medium level (.7 miles) as a warm up to weight training but want to lean out some and increase my endurance, etc. My machine of choice is the eliptical stepper and was wondering if it's better to pace yourself (slow down) so as to make your time on the machine last say 30 min. and cover approx 2.5 miles or go for speed and distance ie: 2 miles in 15 min. Since the idea is to get your heart pumping either would do that but which is more effective? Thanks.