I think the key is to do it often. I found that when I put the imax workouts in my rotation at least once a week, I see rapid improvement in my endurance level, and I do mean rapid! To maintain that level ( and not improve ) I find that one Imax every 2 -2 1/2 weeks does the trick. Just did Imax 2 this morning after about 3 wks, got through all the blasts except cursed number 9, which I had to modify the very last go-around. It all depends on what you are looking for. I would try to do just the first five intervals first. Continue adding segments as you find your cardiovascular fitness improves. Before you know it you will have em all down!