The honeymoon with the Body Blast series isn't over, so this could change, but right now it's Supersets. Imax (thanks to Annette's urging) is the smartest Cathe purchase I've probably made (that said, I do not regret a single Cathe purchase - they've all been well worth it). Imax has done the most for my cardiovascular endurance. Sometimes I have to psyche myself up to do it, but I'm always glad I did.