I don't know that anyone could give you numbers on this one. Part of the problem is that since running uses different muscles, or uses them differently, than step does, your body may have to work harder cardio-wise than you might expect just to keep putting one foot in front of the other.(I'm assuming here that you don't already run as a normal part of your cardio). I was thinking at first that I would just recommend that you take the time you would spend on a Cathe step tape (average seems to be about 7-9 min. warm-up, 40-47 min main cardio, 7-9 min cooldown), walk briskly for the warm-up and cooldown times and walk/jog/run at whatever pace feels like the same percieved rate of exertion you would use with Cathe for the same amount of time she uses for the main cardio. But then I realized that going that long if you're new to running would be to set yourself up for injury. So I guess my wishy-washy advice is to walk a lot, run a little, and know that you're not going to lose your conditining from just a week without step. --Karen