My favorite of all of Cathe's strength workouts is the Slow and Heavy series. However, that might not be the best one to start out with when building strength. MIS works each muscle group of the upperbody in about 6 or 7 min, whereas the Pure Strength series works each for 10-12 min. MIS is almost like an endurance workout in that it moves fairly quickly, however, Cathe uses a 35# barbell for each body part, as opposed to using lighter weight for some, like she does in Power Hour. I really like Pure Strength series and found that it built a great foundation of strength before moving onto the Slow and Heavy tapes. And I LOVE Pure Strength's legs workout. That is my favorite Cathe leg workout of all time.