I have made good progress in gaining muscle, but I just have a hard time getting through Mega Step Blast on the 8-inch step. I've been doing this tape for a couple months now regularly. I also do The FIRM and really think that has helped me to tone up and I am more sculpted, but when it comes to cardio, I am a WIMP. I just can't seem to improve. I workout 5-6 days a week doing cardio and about 3 days a week weight lifting. I am not overweight. I'd like to get through MSB using a 8-inch step. I can do it on a 6-inch and that is hard, but I do get through it and with good form. But whenever I try this on the 8-inch... well, it just poops me out. How can I improve?