I've yet to do the entire 'workout', however I have been using the equipment daily. As with all workouts, it is important to focus on the muscle group one is engaging, so I use the muscles in my upper thigh and butt region. I feel I am getting a tremendous workout. When I first 'jumped on' the equipment I did feel some soreness in my knees, however that was because I was actually pulling my legs inward using the lower portion of my leg, instead of using the targeted muscle group.