I think there is a workout curve for each level, but my level is still level 3 which I started at. I don't know if my month 5 is like month 2 for level 4 or month 8 for level 1, but I CAN tell you they do indeed make it harder every month.. oh BOY do they ever! My shoulders are screaming today with the pushups he tried to get me to do!
The cardio is also at two levels.. I asked in the beginning. So for example the Gotham Body workout.. level one and two get one workout and level three and four get another one.
I really like Bob too, but what scares me is someone posted that Mike was a LOT harder than Bob!!

After getting the next DVD, I think I am putting my subscription on hold because as far as the upper body stuff, my strength has not preogressed as the DVD wants me to be.. Stuff with weights and the bands are fine. it's just the exercises that use our own body weight, like dolphins, planks, pushups.. etc. He makes them harder every month!!