Warm up for 5 minutes then to 8 sets of max setting at ~96 step/min (used to be 100 but I am getting old) for a minute and then rest for 90 sec. Now that it is summer and I am trying to get my boys to run I am doing that, but I am pretty sure that I will go back to this routine. I do some circuit weight training for my core muscles right after so I keep my heart rate up for another 25 minutes. In all, I keep it up for 50 minutes while doing exercise that increases my strength and I think it is a good combination.