Mar:
yes, Bootcamp is circuit in style, but of course it has an interval effect with those one minute cardios to which you give your all. Quite honestly I feel Bootcamp to be as tough as the Imaxes. I think if you can do Bootcamp and you have mastered most of the third stage most advanced steps for the intervals in Gin Miller's Intense Moves you are completely ready for the Imaxes. They will be a challenge to begin with, but not just for you, they are a challenge to everybody, including Cathe and her crew who rehearse them for several weeks to improve their cardiovascular conditioning before filming!
Cathe's intrvals are more intesne than Gin's. Imax 1 has one minute intervals that repeat the same move over and over again forthe duration. Some are easier than others, some you will love, others are horrid! Imax 2 uses a combo of moves in each interval and is for that reason more interesting in my opinion. The music for Imax 2 is way better than that for imax 1, it will sweep you along with it until suddenly you realize how hard you are working.
It's fine to get these workouts nd larn them slowly, increasing your endurance bit by bit, and modifying moves where you need to. Some of the moves may always challenge you and some may aggravate knees, etc, but there are many moves from imax 1 that you could sub for some of the intervals of imax 2 if they do not suit you. So, there are many ways to make it work for you.
Please don't think that you have no business doing either of these workouts until you are in tip top athletic condition: the whole point is to use them to help you reach that state. Even if all you can do to begin with is the first half of each, that is great. Then every two weeks or so, you add another interval on until you have accomplished the whole thing.
Look at Cathe's video clips and see what you think. There are many devotees of these workouts here who can enthuse more. Personally, I prefer circuits to intervals and so have not done either video since about May I think. Just personal preference. They are awesome workouts, especially Imax 2.
Clare