Yes, Step Blast is a calorie burner. I just did it on an 8" step last week and burned 488 calories. I only do IMAX 3 on a 6" step and I burn an average of 421 calories. These are two of my all-time favorites. They are both really intense. IMAX 2 I burn an average of 407 calories. IMAX 1 about 416. I had started to do IMAX 1 on 8" as well. I find IMAX 1 and 3 to be about the same level and IMAX 2 the easiest of the three (not to say that it's easy). I don't think I would ever do IMAX 3 on 8" because of the choreography and the intensity. Even though Step Blast only has the blasts at the end, it is quite a challenge after running through all the step combos.
Marcy